DataTable.Load 方法

定義

命名空間:: System.Data

組件:: netstandard.dll, System.Data.Common.dll

組件:: System.Data.Common.dll

組件:: System.Data.dll

組件:: netstandard.dll

重要

部分資訊涉及發行前產品，在發行之前可能會有大幅修改。 Microsoft 對此處提供的資訊，不做任何明確或隱含的瑕疵擔保。

利用提供的 IDataReader資料來源來填入 aDataTable。如果已經 DataTable 包含資料列，來自資料來源的輸入資料會與現有的資料列合併。

多載

名稱	Description
Load(IDataReader)	利用提供的 IDataReader資料來源來填入 aDataTable。如果已經 DataTable 包含資料列，來自資料來源的輸入資料會與現有的資料列合併。
Load(IDataReader, LoadOption)	利用提供的 IDataReader資料來源來填入 aDataTable。若已 `DataTable` 包含列數，則根據參數值 `loadOption` ，資料來源的輸入資料會與現有資料列合併。
Load(IDataReader, LoadOption, FillErrorEventHandler)	利用錯誤處理代理所提供的IDataReader資料，填DataTable入資料來源的值。

範例

以下範例展示了呼叫該 Load 方法時涉及的幾個問題。首先，範例聚焦於結構問題，包括從已載 IDataReader入的結構推斷結構，接著處理不相容的結構，以及缺少或新增欄位的結構。接著範例聚焦於資料議題，包括處理各種載入選項。

備註

此範例展示了如何使用其中一個超載版本的 Load。其他可能可用的範例，請參閱個別超載主題。

static void Main()
{
    // This example examines a number of scenarios involving the
    // DataTable.Load method.
    Console.WriteLine("Load a DataTable and infer its schema:");

    // The table has no schema. The Load method will infer the
    // schema from the IDataReader:
    DataTable table = new DataTable();

    // Retrieve a data reader, based on the Customers data. In
    // an application, this data might be coming from a middle-tier
    // business object:
    DataTableReader reader = new DataTableReader(GetCustomers());

    table.Load(reader);
    PrintColumns(table);

    Console.WriteLine(" ============================= ");
    Console.WriteLine("Load a DataTable from an incompatible IDataReader:");

    // Create a table with a single integer column. Attempt
    // to load data from a reader with a schema that is
    // incompatible. Note the exception, determined
    // by the particular incompatibility:
    table = GetIntegerTable();
    reader = new DataTableReader(GetStringTable());
    try
    {
        table.Load(reader);
    }
    catch (Exception ex)
    {
        Console.WriteLine(ex.GetType().Name + ":" + ex.Message);
    }

    Console.WriteLine(" ============================= ");
    Console.WriteLine(
        "Load a DataTable with an IDataReader that has extra columns:");

    // Note that loading a reader with extra columns adds
    // the columns to the existing table, if possible:
    table = GetIntegerTable();
    reader = new DataTableReader(GetCustomers());
    table.Load(reader);
    PrintColumns(table);

    Console.WriteLine(" ============================= ");
    Console.WriteLine(
        "Load a DataTable with an IDataReader that has missing columns:");

    // Note that loading a reader with missing columns causes
    // the columns to be filled with null data, if possible:
    table = GetCustomers();
    reader = new DataTableReader(GetIntegerTable());
    table.Load(reader);
    PrintColumns(table);

    // Demonstrate the various possibilites when loading data into
    // a DataTable that already contains data.
    Console.WriteLine(" ============================= ");
    Console.WriteLine("Demonstrate data considerations:");
    Console.WriteLine("Current value, Original value, (RowState)");
    Console.WriteLine(" ============================= ");
    Console.WriteLine("Original table:");

    table = SetupModifiedRows();
    DisplayRowState(table);

    Console.WriteLine(" ============================= ");
    Console.WriteLine("Data in IDataReader to be loaded:");
    DisplayRowState(GetChangedCustomers());

    PerformDemo(LoadOption.OverwriteChanges);
    PerformDemo(LoadOption.PreserveChanges);
    PerformDemo(LoadOption.Upsert);

    Console.WriteLine("Press any key to continue.");
    Console.ReadKey();
}

private static void DisplayRowState(DataTable table)
{
    for (int i = 0; i <= table.Rows.Count - 1; i++)
    {
        object current = "--";
        object original = "--";
        DataRowState rowState = table.Rows[i].RowState;

        // Attempt to retrieve the current value, which doesn't exist
        // for deleted rows:
        if (rowState != DataRowState.Deleted)
        {
            current = table.Rows[i]["Name", DataRowVersion.Current];
        }

        // Attempt to retrieve the original value, which doesn't exist
        // for added rows:
        if (rowState != DataRowState.Added)
        {
            original = table.Rows[i]["Name", DataRowVersion.Original];
        }
        Console.WriteLine("{0}: {1}, {2} ({3})", i, current,
            original, rowState);
    }
}

private static DataTable GetChangedCustomers()
{
    // Create sample Customers table.
    DataTable table = new DataTable();

    // Create two columns, ID and Name.
    DataColumn idColumn = table.Columns.Add("ID", typeof(int));
    table.Columns.Add("Name", typeof(string));

    // Set the ID column as the primary key column.
    table.PrimaryKey = new DataColumn[] { idColumn };

    table.Rows.Add(new object[] { 0, "XXX" });
    table.Rows.Add(new object[] { 1, "XXX" });
    table.Rows.Add(new object[] { 2, "XXX" });
    table.Rows.Add(new object[] { 3, "XXX" });
    table.Rows.Add(new object[] { 4, "XXX" });
    table.AcceptChanges();
    return table;
}

private static DataTable GetCustomers()
{
    // Create sample Customers table, in order
    // to demonstrate the behavior of the DataTableReader.
    DataTable table = new DataTable();

    // Create two columns, ID and Name.
    DataColumn idColumn = table.Columns.Add("ID", typeof(int));
    table.Columns.Add("Name", typeof(string));

    // Set the ID column as the primary key column.
    table.PrimaryKey = new DataColumn[] { idColumn };

    table.Rows.Add(new object[] { 0, "Mary" });
    table.Rows.Add(new object[] { 1, "Andy" });
    table.Rows.Add(new object[] { 2, "Peter" });
    table.AcceptChanges();
    return table;
}

private static DataTable GetIntegerTable()
{
    // Create sample Customers table, in order
    // to demonstrate the behavior of the DataTableReader.
    DataTable table = new DataTable();

    // Create two columns, ID and Name.
    DataColumn idColumn = table.Columns.Add("ID", typeof(int));

    // Set the ID column as the primary key column.
    table.PrimaryKey = new DataColumn[] { idColumn };

    table.Rows.Add(new object[] { 4 });
    table.Rows.Add(new object[] { 5 });
    table.AcceptChanges();
    return table;
}

private static DataTable GetStringTable()
{
    // Create sample Customers table, in order
    // to demonstrate the behavior of the DataTableReader.
    DataTable table = new DataTable();

    // Create two columns, ID and Name.
    DataColumn idColumn = table.Columns.Add("ID", typeof(string));

    // Set the ID column as the primary key column.
    table.PrimaryKey = new DataColumn[] { idColumn };

    table.Rows.Add(new object[] { "Mary" });
    table.Rows.Add(new object[] { "Andy" });
    table.Rows.Add(new object[] { "Peter" });
    table.AcceptChanges();
    return table;
}

private static void PerformDemo(LoadOption optionForLoad)
{

    // Load data into a DataTable, retrieve a DataTableReader containing
    // different data, and call the Load method. Depending on the
    // LoadOption value passed as a parameter, this procedure displays
    // different results in the DataTable.
    Console.WriteLine(" ============================= ");
    Console.WriteLine("table.Load(reader, {0})", optionForLoad);
    Console.WriteLine(" ============================= ");

    DataTable table = SetupModifiedRows();
    DataTableReader reader = new DataTableReader(GetChangedCustomers());
    table.RowChanging +=new DataRowChangeEventHandler(HandleRowChanging);

    table.Load(reader, optionForLoad);
    Console.WriteLine();
    DisplayRowState(table);
}

private static void PrintColumns(DataTable table)
{
    // Loop through all the rows in the DataTableReader
    foreach (DataRow row in table.Rows)
    {
        for (int i = 0; i < table.Columns.Count; i++)
        {
            Console.Write(row[i] + " ");
        }
        Console.WriteLine();
    }
}

private static DataTable SetupModifiedRows()
{
    // Fill a DataTable with customer info, and
    // then modify, delete, and add rows.

    DataTable table = GetCustomers();
    // Row 0 is unmodified.
    // Row 1 is modified.
    // Row 2 is deleted.
    // Row 3 is added.
    table.Rows[1]["Name"] = "Sydney";
    table.Rows[2].Delete();
    DataRow row = table.NewRow();
    row["ID"] = 3;
    row["Name"] = "Melony";
    table.Rows.Add(row);

    // Note that the code doesn't call
    // table.AcceptChanges()
    return table;
}

static void HandleRowChanging(object sender, DataRowChangeEventArgs e)
{
    Console.WriteLine(
        "RowChanging event: ID = {0}, action = {1}", e.Row["ID"],
        e.Action);
}

Sub Main()
  Dim table As New DataTable()

  ' This example examines a number of scenarios involving the 
  ' DataTable.Load method.
  Console.WriteLine("Load a DataTable and infer its schema:")

  ' Retrieve a data reader, based on the Customers data. In
  ' an application, this data might be coming from a middle-tier
  ' business object:
  Dim reader As New DataTableReader(GetCustomers())

  ' The table has no schema. The Load method will infer the 
  ' schema from the IDataReader:
  table.Load(reader)
  PrintColumns(table)

  Console.WriteLine(" ============================= ")
  Console.WriteLine("Load a DataTable from an incompatible IDataReader:")

  ' Create a table with a single integer column. Attempt
  ' to load data from a reader with a schema that is 
  ' incompatible. Note the exception, determined
  ' by the particular incompatibility:
  table = GetIntegerTable()
  reader = New DataTableReader(GetStringTable())
  Try
    table.Load(reader)
  Catch ex As Exception
    Console.WriteLine(ex.GetType.Name & ":" & ex.Message())
  End Try

  Console.WriteLine(" ============================= ")
  Console.WriteLine( _
      "Load a DataTable with an IDataReader that has extra columns:")

  ' Note that loading a reader with extra columns adds
  ' the columns to the existing table, if possible:
  table = GetIntegerTable()
  reader = New DataTableReader(GetCustomers())
  table.Load(reader)
  PrintColumns(table)

  Console.WriteLine(" ============================= ")
  Console.WriteLine( _
      "Load a DataTable with an IDataReader that has missing columns:")

  ' Note that loading a reader with missing columns causes 
  ' the columns to be filled with null data, if possible:
  table = GetCustomers()
  reader = New DataTableReader(GetIntegerTable())
  table.Load(reader)
  PrintColumns(table)

  ' Demonstrate the various possibilites when loading data into
  ' a DataTable that already contains data.
  Console.WriteLine(" ============================= ")
  Console.WriteLine("Demonstrate data considerations:")
  Console.WriteLine("Current value, Original value, (RowState)")
  Console.WriteLine(" ============================= ")
  Console.WriteLine("Original table:")

  table = SetupModifiedRows()
  DisplayRowState(table)

  Console.WriteLine(" ============================= ")
  Console.WriteLine("Data in IDataReader to be loaded:")
  DisplayRowState(GetChangedCustomers())

  PerformDemo(LoadOption.OverwriteChanges)
  PerformDemo(LoadOption.PreserveChanges)
  PerformDemo(LoadOption.Upsert)

  Console.WriteLine("Press any key to continue.")
  Console.ReadKey()
End Sub

Private Sub DisplayRowState(ByVal table As DataTable)
  For i As Integer = 0 To table.Rows.Count - 1
    Dim current As Object = "--"
    Dim original As Object = "--"
    Dim rowState As DataRowState = table.Rows(i).RowState

    ' Attempt to retrieve the current value, which doesn't exist
    ' for deleted rows:
    If rowState <> DataRowState.Deleted Then
      current = table.Rows(i)("Name", DataRowVersion.Current)
    End If

    ' Attempt to retrieve the original value, which doesn't exist
    ' for added rows:
    If rowState <> DataRowState.Added Then
      original = table.Rows(i)("Name", DataRowVersion.Original)
    End If
    Console.WriteLine("{0}: {1}, {2} ({3})", i, current, original, rowState)
  Next
End Sub

Private Function GetChangedCustomers() As DataTable
  ' Create sample Customers table.
  Dim table As New DataTable

  ' Create two columns, ID and Name.
  Dim idColumn As DataColumn = table.Columns.Add("ID", GetType(Integer))
  table.Columns.Add("Name", GetType(String))

  ' Set the ID column as the primary key column.
  table.PrimaryKey = New DataColumn() {idColumn}

  table.Rows.Add(New Object() {0, "XXX"})
  table.Rows.Add(New Object() {1, "XXX"})
  table.Rows.Add(New Object() {2, "XXX"})
  table.Rows.Add(New Object() {3, "XXX"})
  table.Rows.Add(New Object() {4, "XXX"})
  table.AcceptChanges()
  Return table
End Function

Private Function GetCustomers() As DataTable
  ' Create sample Customers table.
  Dim table As New DataTable

  ' Create two columns, ID and Name.
  Dim idColumn As DataColumn = table.Columns.Add("ID", GetType(Integer))
  table.Columns.Add("Name", GetType(String))

  ' Set the ID column as the primary key column.
  table.PrimaryKey = New DataColumn() {idColumn}

  table.Rows.Add(New Object() {0, "Mary"})
  table.Rows.Add(New Object() {1, "Andy"})
  table.Rows.Add(New Object() {2, "Peter"})
  table.AcceptChanges()
  Return table
End Function

Private Function GetIntegerTable() As DataTable
  ' Create sample table with a single Int32 column.
  Dim table As New DataTable

  Dim idColumn As DataColumn = table.Columns.Add("ID", GetType(Integer))

  ' Set the ID column as the primary key column.
  table.PrimaryKey = New DataColumn() {idColumn}

  table.Rows.Add(New Object() {4})
  table.Rows.Add(New Object() {5})
  table.AcceptChanges()
  Return table
End Function

Private Function GetStringTable() As DataTable
  ' Create sample table with a single String column.
  Dim table As New DataTable

  Dim idColumn As DataColumn = table.Columns.Add("ID", GetType(String))

  ' Set the ID column as the primary key column.
  table.PrimaryKey = New DataColumn() {idColumn}

  table.Rows.Add(New Object() {"Mary"})
  table.Rows.Add(New Object() {"Andy"})
  table.Rows.Add(New Object() {"Peter"})
  table.AcceptChanges()
  Return table
End Function

Private Sub PerformDemo(ByVal optionForLoad As LoadOption)

  ' Load data into a DataTable, retrieve a DataTableReader containing
  ' different data, and call the Load method. Depending on the
  ' LoadOption value passed as a parameter, this procedure displays
  ' different results in the DataTable.
  Console.WriteLine(" ============================= ")
  Console.WriteLine("table.Load(reader, {0})", optionForLoad)
  Console.WriteLine(" ============================= ")

  Dim table As DataTable = SetupModifiedRows()
  Dim reader As New DataTableReader(GetChangedCustomers())
  AddHandler table.RowChanging, New _
      DataRowChangeEventHandler(AddressOf HandleRowChanging)

  table.Load(reader, optionForLoad)
  Console.WriteLine()
  DisplayRowState(table)
End Sub

Private Sub PrintColumns( _
   ByVal table As DataTable)

  ' Loop through all the rows in the DataTableReader.
  For Each row As DataRow In table.Rows
    For Each col As DataColumn In table.Columns
      Console.Write(row(col).ToString() & " ")
    Next
    Console.WriteLine()
  Next
End Sub

Private Function SetupModifiedRows() As DataTable
  ' Fill a DataTable with customer info, and 
  ' then modify, delete, and add rows.

  Dim table As DataTable = GetCustomers()
  ' Row 0 is unmodified.
  ' Row 1 is modified.
  ' Row 2 is deleted.
  ' Row 3 is added.
  table.Rows(1)("Name") = "Sydney"
  table.Rows(2).Delete()
  Dim row As DataRow = table.NewRow
  row("ID") = 3
  row("Name") = "Melony"
  table.Rows.Add(row)

  ' Note that the code doesn't call
  ' table.AcceptChanges()
  Return table
End Function

Private Sub HandleRowChanging(ByVal sender As Object, _
  ByVal e As System.Data.DataRowChangeEventArgs)
  Console.WriteLine( _
      "RowChanging event: ID = {0}, action = {1}", e.Row("ID"), _
      e.Action)
End Sub

備註

此 Load 方法可用於多種常見情境，皆圍繞從指定資料來源取得資料並將其加入目前的資料容器（此例 DataTable為）。這些情境描述了的 DataTable標準使用，描述其更新與合併行為。

A DataTable 與單一主要資料來源同步或更新。 DataTable軌跡會改變，使得與主要資料來源同步。此外，A DataTable 也能接受來自一個或多個次級資料來源的增量資料。他們 DataTable 不負責追蹤變更以允許與次級資料來源同步。

根據這兩個假設的資料來源，使用者很可能需要以下其中一種行為：

從主要資料來源初始化 DataTable 。在此情境中，使用者希望以主要資料來源的值初始化一個空 DataTable 位。之後使用者打算將變更傳回主要資料來源。
保留變更並重新同步於主要資料來源。在此情境中，使用者希望將 DataTable 前一個情境中已填入的資料，並與主要資料來源進行增量同步，保留在 DataTable.
來自次級資料來源的增量資料流。在此情境中，使用者希望將一個或多個次要資料來源的變更合併，並將這些變更傳回主要資料來源。

這個 Load 方法讓所有這些情境都成為可能。除了其中一個外，這個方法的超載都允許你指定載入選項參數，指示已在 DataTable 合併中與列的列如何被載入。（不允許你指定行為的超載會使用預設的載入選項。）下表說明列舉所 LoadOption 提供的三種載荷選項。在每種情況下，描述都顯示當資料列的主鍵與現有列的主鍵相符時的行為。

裝載選項	說明
`PreserveChanges` (預設值)	更新該列的原始版本，並更新該列的值。
`OverwriteChanges`	更新該列目前及原始版本的下一列值。
`Upsert`	更新該列的當前版本，並輸入該列的值。

一般而言， PreserveChanges 與 OverwriteChanges 選項是針對使用者需要與 DataSet 主要資料來源同步其變更的情況。此 Upsert 選項有助於彙整來自一個或多個次級資料來源的變更。

Load(IDataReader)

來源:: DataTable.cs

來源:: DataTable.cs

來源:: DataTable.cs

來源:: DataTable.cs

來源:: DataTable.cs

利用提供的 IDataReader資料來源來填入 aDataTable。如果已經 DataTable 包含資料列，來自資料來源的輸入資料會與現有的資料列合併。

public:
 void Load(System::Data::IDataReader ^ reader);

[System.Diagnostics.CodeAnalysis.RequiresUnreferencedCode("Members from types used in the expression column to be trimmed if not referenced directly.")]
public void Load(System.Data.IDataReader reader);

public void Load(System.Data.IDataReader reader);

[<System.Diagnostics.CodeAnalysis.RequiresUnreferencedCode("Members from types used in the expression column to be trimmed if not referenced directly.")>]
member this.Load : System.Data.IDataReader -> unit

member this.Load : System.Data.IDataReader -> unit

Public Sub Load (reader As IDataReader)

參數

reader: IDataReader

一個 IDataReader 提供結果集合的

屬性: RequiresUnreferencedCodeAttribute

範例

以下範例展示了呼叫該 Load 方法時涉及的幾個問題。首先，範例聚焦於結構問題，包括從已載 IDataReader入的結構推斷結構，接著處理不相容的結構，以及缺少或新增欄位的結構。範例接著呼叫該 Load 方法，並在載入操作前後顯示資料。

static void Main()
{
    // This example examines a number of scenarios involving the
    // DataTable.Load method.
    Console.WriteLine("Load a DataTable and infer its schema:");

    // The table has no schema. The Load method will infer the
    // schema from the IDataReader:
    DataTable table = new DataTable();

    // Retrieve a data reader, based on the Customers data. In
    // an application, this data might be coming from a middle-tier
    // business object:
    DataTableReader reader = new DataTableReader(GetCustomers());

    table.Load(reader);
    PrintColumns(table);

    Console.WriteLine(" ============================= ");
    Console.WriteLine(
        "Load a DataTable from an incompatible IDataReader:");

    // Create a table with a single integer column. Attempt
    // to load data from a reader with a schema that is
    // incompatible. Note the exception, determined
    // by the particular incompatibility:
    table = GetIntegerTable();
    reader = new DataTableReader(GetStringTable());
    try
    {
        table.Load(reader);
    }
    catch (Exception ex)
    {
        Console.WriteLine(ex.GetType().Name + ":" + ex.Message);
    }

    Console.WriteLine(" ============================= ");
    Console.WriteLine(
        "Load a DataTable with an IDataReader that has extra columns:");

    // Note that loading a reader with extra columns adds
    // the columns to the existing table, if possible:
    table = GetIntegerTable();
    reader = new DataTableReader(GetCustomers());
    table.Load(reader);
    PrintColumns(table);

    Console.WriteLine(" ============================= ");
    Console.WriteLine(
        "Load a DataTable with an IDataReader that has missing columns:");

    // Note that loading a reader with missing columns causes
    // the columns to be filled with null data, if possible:
    table = GetCustomers();
    reader = new DataTableReader(GetIntegerTable());
    table.Load(reader);
    PrintColumns(table);

    // Demonstrate the various possibilites when loading data
    // into a DataTable that already contains data.
    Console.WriteLine(" ============================= ");
    Console.WriteLine("Demonstrate data considerations:");
    Console.WriteLine("Current value, Original value, (RowState)");
    Console.WriteLine(" ============================= ");
    Console.WriteLine("Original table:");

    table = SetupModifiedRows();
    DisplayRowState(table);

    Console.WriteLine(" ============================= ");
    Console.WriteLine("Data in IDataReader to be loaded:");
    DisplayRowState(GetChangedCustomers());

    // Load data into a DataTable, retrieve a DataTableReader
    // containing different data, and call the Load method.
    Console.WriteLine(" ============================= ");
    Console.WriteLine("table.Load(reader)");
    Console.WriteLine(" ============================= ");

    table = SetupModifiedRows();
    reader = new DataTableReader(GetChangedCustomers());
    table.Load(reader);
    DisplayRowState(table);

    Console.WriteLine("Press any key to continue.");
    Console.ReadKey();
}

private static void DisplayRowState(DataTable table)
{
    for (int i = 0; i <= table.Rows.Count - 1; i++)
    {
        object current = "--";
        object original = "--";
        DataRowState rowState = table.Rows[i].RowState;

        // Attempt to retrieve the current value, which doesn't exist
        // for deleted rows:
        if (rowState != DataRowState.Deleted)
        {
            current = table.Rows[i]["Name", DataRowVersion.Current];
        }

        // Attempt to retrieve the original value, which doesn't exist
        // for added rows:
        if (rowState != DataRowState.Added)
        {
            original = table.Rows[i]["Name", DataRowVersion.Original];
        }
        Console.WriteLine("{0}: {1}, {2} ({3})", i,
            current, original, rowState);
    }
}

private static DataTable GetChangedCustomers()
{
    // Create sample Customers table.
    DataTable table = new DataTable();

    // Create two columns, ID and Name.
    DataColumn idColumn = table.Columns.Add("ID",
        typeof(int));
    table.Columns.Add("Name", typeof(string));

    // Set the ID column as the primary key column.
    table.PrimaryKey = new DataColumn[] { idColumn };

    table.Rows.Add(new object[] { 1, "XXX" });
    table.Rows.Add(new object[] { 2, "XXX" });
    table.Rows.Add(new object[] { 3, "XXX" });
    table.Rows.Add(new object[] { 4, "XXX" });
    table.Rows.Add(new object[] { 5, "XXX" });
    table.Rows.Add(new object[] { 6, "XXX" });
    table.AcceptChanges();
    return table;
}

private static DataTable GetCustomers()
{
    // Create sample Customers table, in order
    // to demonstrate the behavior of the DataTableReader.
    DataTable table = new DataTable();

    // Create two columns, ID and Name.
    DataColumn idColumn = table.Columns.Add("ID",
        typeof(int));
    table.Columns.Add("Name", typeof(string));

    // Set the ID column as the primary key column.
    table.PrimaryKey = new DataColumn[] { idColumn };

    table.Rows.Add(new object[] { 1, "Mary" });
    table.Rows.Add(new object[] { 2, "Andy" });
    table.Rows.Add(new object[] { 3, "Peter" });
    table.Rows.Add(new object[] { 4, "Russ" });
    table.AcceptChanges();
    return table;
}

private static DataTable GetIntegerTable()
{
    // Create sample Customers table, in order
    // to demonstrate the behavior of the DataTableReader.
    DataTable table = new DataTable();

    // Create two columns, ID and Name.
    DataColumn idColumn = table.Columns.Add("ID",
        typeof(int));

    // Set the ID column as the primary key column.
    table.PrimaryKey = new DataColumn[] { idColumn };

    table.Rows.Add(new object[] { 5 });
    table.Rows.Add(new object[] { 6 });
    table.Rows.Add(new object[] { 7 });
    table.Rows.Add(new object[] { 8 });
    table.AcceptChanges();
    return table;
}

private static DataTable GetStringTable()
{
    // Create sample Customers table, in order
    // to demonstrate the behavior of the DataTableReader.
    DataTable table = new DataTable();

    // Create two columns, ID and Name.
    DataColumn idColumn = table.Columns.Add("ID",
        typeof(string));

    // Set the ID column as the primary key column.
    table.PrimaryKey = new DataColumn[] { idColumn };

    table.Rows.Add(new object[] { "Mary" });
    table.Rows.Add(new object[] { "Andy" });
    table.Rows.Add(new object[] { "Peter" });
    table.Rows.Add(new object[] { "Russ" });
    table.AcceptChanges();
    return table;
}

private static void PrintColumns(DataTable table)
{
    // Loop through all the rows in the DataTableReader
    foreach (DataRow row in table.Rows)
    {
        for (int i = 0; i < table.Columns.Count; i++)
        {
            Console.Write(row[i] + " ");
        }
        Console.WriteLine();
    }
}

private static DataTable SetupModifiedRows()
{
    // Fill a DataTable with customer info, and
    // then modify, delete, and add rows.

    DataTable table = GetCustomers();
    // Row 0 is unmodified.
    // Row 1 is modified.
    // Row 2 is deleted.
    // Row 5 is added.
    table.Rows[1]["Name"] = "Sydney";
    table.Rows[2].Delete();
    DataRow row = table.NewRow();
    row["ID"] = 5;
    row["Name"] = "Melony";
    table.Rows.Add(row);

    // Note that the code doesn't call
    // table.AcceptChanges()
    return table;
}

Sub Main()
  ' This example examines a number of scenarios involving the 
  ' DataTable.Load method.
  Console.WriteLine("Load a DataTable and infer its schema:")

  ' The table has no schema. The Load method will infer the 
  ' schema from the IDataReader:
  Dim table As New DataTable()

  ' Retrieve a data reader, based on the Customers data. In
  ' an application, this data might be coming from a middle-tier
  ' business object:
  Dim reader As New DataTableReader(GetCustomers())

  table.Load(reader)
  PrintColumns(table)

  Console.WriteLine(" ============================= ")
  Console.WriteLine( _
      "Load a DataTable from an incompatible IDataReader:")

  ' Create a table with a single integer column. Attempt
  ' to load data from a reader with a schema that is 
  ' incompatible. Note the exception, determined
  ' by the particular incompatibility:
  table = GetIntegerTable()
  reader = New DataTableReader(GetStringTable())
  Try
    table.Load(reader)
  Catch ex As Exception
    Console.WriteLine(ex.GetType.Name & ":" & ex.Message())
  End Try

  Console.WriteLine(" ============================= ")
  Console.WriteLine( _
      "Load a DataTable with an IDataReader that has extra columns:")

  ' Note that loading a reader with extra columns adds
  ' the columns to the existing table, if possible:
  table = GetIntegerTable()
  reader = New DataTableReader(GetCustomers())
  table.Load(reader)
  PrintColumns(table)

  Console.WriteLine(" ============================= ")
      Console.WriteLine( _
          "Load a DataTable with an IDataReader that has missing columns:")

  ' Note that loading a reader with missing columns causes 
  ' the columns to be filled with null data, if possible:
  table = GetCustomers()
  reader = New DataTableReader(GetIntegerTable())
  table.Load(reader)
  PrintColumns(table)

  ' Demonstrate the various possibilites when loading data into
  ' a DataTable that already contains data.
  Console.WriteLine(" ============================= ")
  Console.WriteLine("Demonstrate data considerations:")
  Console.WriteLine("Current value, Original value, (RowState)")
  Console.WriteLine(" ============================= ")
  Console.WriteLine("Original table:")

  table = SetupModifiedRows()
  DisplayRowState(table)

  Console.WriteLine(" ============================= ")
  Console.WriteLine("Data in IDataReader to be loaded:")
  DisplayRowState(GetChangedCustomers())

  ' Load data into a DataTable, retrieve a DataTableReader 
  ' containing different data, and call the Load method. 
  Console.WriteLine(" ============================= ")
  Console.WriteLine("table.Load(reader)")
  Console.WriteLine(" ============================= ")

  table = SetupModifiedRows()
  reader = New DataTableReader(GetChangedCustomers())
  table.Load(reader)
  DisplayRowState(table)

  Console.WriteLine("Press any key to continue.")
  Console.ReadKey()
End Sub

Private Sub DisplayRowState(ByVal table As DataTable)
  For i As Integer = 0 To table.Rows.Count - 1
    Dim current As Object = "--"
    Dim original As Object = "--"
    Dim rowState As DataRowState = table.Rows(i).RowState

    ' Attempt to retrieve the current value, which doesn't exist
    ' for deleted rows:
    If rowState <> DataRowState.Deleted Then
      current = table.Rows(i)("Name", DataRowVersion.Current)
    End If

    ' Attempt to retrieve the original value, which doesn't exist
    ' for added rows:
    If rowState <> DataRowState.Added Then
      original = table.Rows(i)("Name", DataRowVersion.Original)
    End If
    Console.WriteLine("{0}: {1}, {2} ({3})", i, _
      current, original, rowState)
  Next
End Sub

Private Function GetChangedCustomers() As DataTable
  ' Create sample Customers table.
  Dim table As New DataTable

  ' Create two columns, ID and Name.
  Dim idColumn As DataColumn = table.Columns.Add("ID", _
      GetType(Integer))
  table.Columns.Add("Name", GetType(String))

  ' Set the ID column as the primary key column.
  table.PrimaryKey = New DataColumn() {idColumn}

  table.Rows.Add(New Object() {1, "XXX"})
  table.Rows.Add(New Object() {2, "XXX"})
  table.Rows.Add(New Object() {3, "XXX"})
  table.Rows.Add(New Object() {4, "XXX"})
  table.Rows.Add(New Object() {5, "XXX"})
  table.Rows.Add(New Object() {6, "XXX"})
  table.AcceptChanges()
  Return table
End Function

Private Function GetCustomers() As DataTable
  ' Create sample Customers table.
  Dim table As New DataTable

  ' Create two columns, ID and Name.
  Dim idColumn As DataColumn = table.Columns.Add("ID", _
      GetType(Integer))
  table.Columns.Add("Name", GetType(String))

  ' Set the ID column as the primary key column.
  table.PrimaryKey = New DataColumn() {idColumn}

  table.Rows.Add(New Object() {1, "Mary"})
  table.Rows.Add(New Object() {2, "Andy"})
  table.Rows.Add(New Object() {3, "Peter"})
  table.Rows.Add(New Object() {4, "Russ"})
  table.AcceptChanges()
  Return table
End Function

Private Function GetIntegerTable() As DataTable
  ' Create sample table with a single Int32 column.
  Dim table As New DataTable

  Dim idColumn As DataColumn = table.Columns.Add("ID", _
      GetType(Integer))

  ' Set the ID column as the primary key column.
  table.PrimaryKey = New DataColumn() {idColumn}

  table.Rows.Add(New Object() {5})
  table.Rows.Add(New Object() {6})
  table.Rows.Add(New Object() {7})
  table.Rows.Add(New Object() {8})
  table.AcceptChanges()
  Return table
End Function

Private Function GetStringTable() As DataTable
  ' Create sample table with a single String column.
  Dim table As New DataTable

  Dim idColumn As DataColumn = table.Columns.Add("ID", _
      GetType(String))

  ' Set the ID column as the primary key column.
  table.PrimaryKey = New DataColumn() {idColumn}

  table.Rows.Add(New Object() {"Mary"})
  table.Rows.Add(New Object() {"Andy"})
  table.Rows.Add(New Object() {"Peter"})
  table.Rows.Add(New Object() {"Russ"})
  table.AcceptChanges()
  Return table
End Function

Private Sub PrintColumns( _
   ByVal table As DataTable)

  ' Loop through all the rows in the DataTableReader.
  For Each row As DataRow In table.Rows
    For Each col As DataColumn In table.Columns
      Console.Write(row(col).ToString() & " ")
    Next
    Console.WriteLine()
  Next
End Sub

Private Function SetupModifiedRows() As DataTable
  ' Fill a DataTable with customer info, and 
  ' then modify, delete, and add rows.

  Dim table As DataTable = GetCustomers()
  ' Row 0 is unmodified.
  ' Row 1 is modified.
  ' Row 2 is deleted.
  ' Row 5 is added.
  table.Rows(1)("Name") = "Sydney"
  table.Rows(2).Delete()
  Dim row As DataRow = table.NewRow
  row("ID") = 5
  row("Name") = "Melony"
  table.Rows.Add(row)

  ' Note that the code doesn't call
  ' table.AcceptChanges()
  Return table
End Function

備註

該 Load 方法會從載 IDataReader入的中取出第一個結果集，並在成功完成後，將讀取器的位置設定為下一個結果集（若有的話）。在轉換資料時，該 Load 方法使用與該 DbDataAdapter.Fill 方法相同的轉換規則。

Load此方法在載入實例資料IDataReader時必須考慮三個特定問題：結構、資料與事件操作。在使用該結構時， Load 方法可能會遇到如下表所述的條件。結構操作適用於所有匯入的結果集，即使沒有資料也一樣。

狀況	行為
它 DataTable 沒有架構。	該 Load 方法根據從匯入的 IDataReader結果集推論出該結構。
它 DataTable 有 schema，但與已載入的 schema 不相容。	該 Load 方法會拋出一個例外，對應於嘗試將資料載入不相容結構時所發生的特定錯誤。
這些結構是相容的，但載入的結果集結構包含不存在於 DataTable的欄位。	此 Load 方法將額外的欄位加入 `DataTable`的結構中。若與 DataTable 載入結果集對應欄位不相容，該方法會拋出例外。該方法同時從結果集中取得所有新增欄位的限制資訊。除了主鍵限制外，此限制資訊僅在載 DataTable 入操作開始時電流中沒有任何欄位時使用。
這些結構是相容的，但載入的結果集結構包含的欄位數少於 `DataTable`。	若缺失欄位有預設值或資料型別為 null， Load 該方法允許新增列，並以預設 `null` 值取代缺失欄位。若無法使用預設值或 `null` ，則 `Load` 該方法會拋出例外。若未提供特定預設值， `Load` 該方法將該值作為 `null` 隱含的預設值。

在考慮方法在資料操作上的行為 Load 之前，請考慮 a DataTable 中的每一列同時維持每欄的當前值與原始值。這些值可能是等價的，也可能不同，若資料自填入 DataTable。更多資訊請參閱列狀態與列版本。

此版本 Load 嘗試保留每列的當前值，保留原始值。（如果你想更細緻地控制輸入資料的行為，請參見 DataTable.Load。）如果現有的列和進入的列包含對應的主鍵值，該列會使用目前的列狀態值處理，否則會被視為新一列。

在事件操作方面， RowChanging 事件發生在每列變更之前，事件 RowChanged 則在每列變更後發生。在每種情況下， Action 傳遞給事件處理器的實例屬性 DataRowChangeEventArgs 都包含與該事件相關的特定動作資訊。此動作值取決於載入操作前該列的狀態。在每個案例中，兩個事件都同時發生，且作用方式相同。該動作可套用於每列的當前或原始版本，或兩者皆適用，視當前列狀態而定。

下表顯示該 Load 方法的行為。最後一列（標示為「（不存在）」）描述了與任何現有列不匹配的輸入列的行為。此表中的每個儲存格描述同一列欄位的當前及原始值，以及 DataRowState 方法完成後 Load 的值。在這種情況下，該方法不允許你指定載入選項，而是使用預設 PreserveChanges的。

現有 DataRowState	方法與事件動作之後 `Load` 的值
已新增	Current = <現有> 原始 = <即將抵達> 狀態 = <修改版> RowAction = ChangeOriginal
已修改	Current = <現有> 原始 = <即將抵達> 狀態 = <修改版> RowAction = ChangeOriginal
已刪除	目前 = <不可用> 原始 = <即將抵達> 狀態 = <已刪除> RowAction = ChangeOriginal
未更改	Current = <進入> 原始 = <即將抵達> 狀態 = <不變> RowAction = ChangeCurrentAndOriginal
（未出席）	Current = <進入> 原始 = <即將抵達> 狀態 = <不變> RowAction = ChangeCurrentAndOriginal

A 中的 DataColumn 值可以透過使用如 ReadOnly 和 AutoIncrement等性質來約束。該 Load 方法以符合欄位屬性定義行為的方式處理此類欄位。 a DataColumn 的唯讀限制僅適用於記憶體中發生的變更。 Load該方法會覆寫只讀欄位的值（如有需要）。

為了決定要用哪個版本的主鍵欄位來比較目前列與輸入列，方法會 Load 使用該列內原始的主鍵值（如果存在的話）。否則，該 Load 方法使用當前版本的主鍵欄位。

另請參閱

適用於

Load(IDataReader, LoadOption)

來源:: DataTable.cs

來源:: DataTable.cs

來源:: DataTable.cs

來源:: DataTable.cs

來源:: DataTable.cs

利用提供的 IDataReader資料來源來填入 aDataTable。若已 DataTable 包含列數，則根據參數值 loadOption ，資料來源的輸入資料會與現有資料列合併。

public:
 void Load(System::Data::IDataReader ^ reader, System::Data::LoadOption loadOption);

[System.Diagnostics.CodeAnalysis.RequiresUnreferencedCode("Using LoadOption may cause members from types used in the expression column to be trimmed if not referenced directly.")]
public void Load(System.Data.IDataReader reader, System.Data.LoadOption loadOption);

public void Load(System.Data.IDataReader reader, System.Data.LoadOption loadOption);

[<System.Diagnostics.CodeAnalysis.RequiresUnreferencedCode("Using LoadOption may cause members from types used in the expression column to be trimmed if not referenced directly.")>]
member this.Load : System.Data.IDataReader * System.Data.LoadOption -> unit

member this.Load : System.Data.IDataReader * System.Data.LoadOption -> unit

Public Sub Load (reader As IDataReader, loadOption As LoadOption)

參數

reader: IDataReader

一個 IDataReader 提供一個或多個結果集的。

loadOption: LoadOption

列舉中的一個值 LoadOption ，表示已在中的 DataTable 列與共用相同主鍵的入列如何結合。

屬性: RequiresUnreferencedCodeAttribute

範例

static void Main()
{
    // This example examines a number of scenarios involving the
    // DataTable.Load method.
    Console.WriteLine("Load a DataTable and infer its schema:");

    // The table has no schema. The Load method will infer the
    // schema from the IDataReader:
    DataTable table = new DataTable();

    // Retrieve a data reader, based on the Customers data. In
    // an application, this data might be coming from a middle-tier
    // business object:
    DataTableReader reader = new DataTableReader(GetCustomers());

    table.Load(reader);
    PrintColumns(table);

    Console.WriteLine(" ============================= ");
    Console.WriteLine(
        "Load a DataTable from an incompatible IDataReader:");

    // Create a table with a single integer column. Attempt
    // to load data from a reader with a schema that is
    // incompatible. Note the exception, determined
    // by the particular incompatibility:
    table = GetIntegerTable();
    reader = new DataTableReader(GetStringTable());
    try
    {
        table.Load(reader);
    }
    catch (Exception ex)
    {
        Console.WriteLine(ex.GetType().Name + ":" + ex.Message);
    }

    Console.WriteLine(" ============================= ");
    Console.WriteLine(
        "Load a DataTable with an IDataReader that has extra columns:");

    // Note that loading a reader with extra columns adds
    // the columns to the existing table, if possible:
    table = GetIntegerTable();
    reader = new DataTableReader(GetCustomers());
    table.Load(reader);
    PrintColumns(table);

    Console.WriteLine(" ============================= ");
    Console.WriteLine(
        "Load a DataTable with an IDataReader that has missing columns:");

    // Note that loading a reader with missing columns causes
    // the columns to be filled with null data, if possible:
    table = GetCustomers();
    reader = new DataTableReader(GetIntegerTable());
    table.Load(reader);
    PrintColumns(table);

    // Demonstrate the various possibilites when loading data into
    // a DataTable that already contains data.
    Console.WriteLine(" ============================= ");
    Console.WriteLine("Demonstrate data considerations:");
    Console.WriteLine("Current value, Original value, (RowState)");
    Console.WriteLine(" ============================= ");
    Console.WriteLine("Original table:");

    table = SetupModifiedRows();
    DisplayRowState(table);

    Console.WriteLine(" ============================= ");
    Console.WriteLine("Data in IDataReader to be loaded:");
    DisplayRowState(GetChangedCustomers());

    PerformDemo(LoadOption.OverwriteChanges);
    PerformDemo(LoadOption.PreserveChanges);
    PerformDemo(LoadOption.Upsert);

    Console.WriteLine("Press any key to continue.");
    Console.ReadKey();
}

private static void DisplayRowState(DataTable table)
{
    for (int i = 0; i <= table.Rows.Count - 1; i++)
    {
        object current = "--";
        object original = "--";
        DataRowState rowState = table.Rows[i].RowState;

        // Attempt to retrieve the current value, which doesn't exist
        // for deleted rows:
        if (rowState != DataRowState.Deleted)
        {
            current = table.Rows[i]["Name", DataRowVersion.Current];
        }

        // Attempt to retrieve the original value, which doesn't exist
        // for added rows:
        if (rowState != DataRowState.Added)
        {
            original = table.Rows[i]["Name", DataRowVersion.Original];
        }
        Console.WriteLine("{0}: {1}, {2} ({3})", i,
            current, original, rowState);
    }
}

private static DataTable GetChangedCustomers()
{
    // Create sample Customers table.
    DataTable table = new DataTable();

    // Create two columns, ID and Name.
    DataColumn idColumn = table.Columns.Add("ID", typeof(int));
    table.Columns.Add("Name", typeof(string));

    // Set the ID column as the primary key column.
    table.PrimaryKey = new DataColumn[] { idColumn };

    table.Rows.Add(new object[] { 0, "XXX" });
    table.Rows.Add(new object[] { 1, "XXX" });
    table.Rows.Add(new object[] { 2, "XXX" });
    table.Rows.Add(new object[] { 3, "XXX" });
    table.Rows.Add(new object[] { 4, "XXX" });
    table.AcceptChanges();
    return table;
}

private static DataTable GetCustomers()
{
    // Create sample Customers table, in order
    // to demonstrate the behavior of the DataTableReader.
    DataTable table = new DataTable();

    // Create two columns, ID and Name.
    DataColumn idColumn = table.Columns.Add("ID", typeof(int));
    table.Columns.Add("Name", typeof(string));

    // Set the ID column as the primary key column.
    table.PrimaryKey = new DataColumn[] { idColumn };

    table.Rows.Add(new object[] { 0, "Mary" });
    table.Rows.Add(new object[] { 1, "Andy" });
    table.Rows.Add(new object[] { 2, "Peter" });
    table.AcceptChanges();
    return table;
}

private static DataTable GetIntegerTable()
{
    // Create sample Customers table, in order
    // to demonstrate the behavior of the DataTableReader.
    DataTable table = new DataTable();

    // Create two columns, ID and Name.
    DataColumn idColumn = table.Columns.Add("ID", typeof(int));

    // Set the ID column as the primary key column.
    table.PrimaryKey = new DataColumn[] { idColumn };

    table.Rows.Add(new object[] { 4 });
    table.Rows.Add(new object[] { 5 });
    table.AcceptChanges();
    return table;
}

private static DataTable GetStringTable()
{
    // Create sample Customers table, in order
    // to demonstrate the behavior of the DataTableReader.
    DataTable table = new DataTable();

    // Create two columns, ID and Name.
    DataColumn idColumn = table.Columns.Add("ID", typeof(string));

    // Set the ID column as the primary key column.
    table.PrimaryKey = new DataColumn[] { idColumn };

    table.Rows.Add(new object[] { "Mary" });
    table.Rows.Add(new object[] { "Andy" });
    table.Rows.Add(new object[] { "Peter" });
    table.AcceptChanges();
    return table;
}

private static void PerformDemo(LoadOption optionForLoad)
{

    // Load data into a DataTable, retrieve a DataTableReader containing
    // different data, and call the Load method. Depending on the
    // LoadOption value passed as a parameter, this procedure displays
    // different results in the DataTable.
    Console.WriteLine(" ============================= ");
    Console.WriteLine("table.Load(reader, {0})", optionForLoad);
    Console.WriteLine(" ============================= ");

    DataTable table = SetupModifiedRows();
    DataTableReader reader = new DataTableReader(GetChangedCustomers());
    table.RowChanging +=new DataRowChangeEventHandler(HandleRowChanging);

    table.Load(reader, optionForLoad);
    Console.WriteLine();
    DisplayRowState(table);
}

private static void PrintColumns(DataTable table)
{
    // Loop through all the rows in the DataTableReader
    foreach (DataRow row in table.Rows)
    {
        for (int i = 0; i < table.Columns.Count; i++)
        {
            Console.Write(row[i] + " ");
        }
        Console.WriteLine();
    }
}

private static DataTable SetupModifiedRows()
{
    // Fill a DataTable with customer info, and
    // then modify, delete, and add rows.

    DataTable table = GetCustomers();
    // Row 0 is unmodified.
    // Row 1 is modified.
    // Row 2 is deleted.
    // Row 3 is added.
    table.Rows[1]["Name"] = "Sydney";
    table.Rows[2].Delete();
    DataRow row = table.NewRow();
    row["ID"] = 3;
    row["Name"] = "Melony";
    table.Rows.Add(row);

    // Note that the code doesn't call
    // table.AcceptChanges()
    return table;
}

static void HandleRowChanging(object sender, DataRowChangeEventArgs e)
{
    Console.WriteLine(
        "RowChanging event: ID = {0}, action = {1}", e.Row["ID"], e.Action);
}

Sub Main()
  Dim table As New DataTable()

  ' This example examines a number of scenarios involving the
  '  DataTable.Load method.
  Console.WriteLine("Load a DataTable and infer its schema:")

  ' Retrieve a data reader, based on the Customers data. In
  ' an application, this data might be coming from a middle-tier
  ' business object:
  Dim reader As New DataTableReader(GetCustomers())

  ' The table has no schema. The Load method will infer the 
  ' schema from the IDataReader:
  table.Load(reader)
  PrintColumns(table)

  Console.WriteLine(" ============================= ")
  Console.WriteLine( _
      "Load a DataTable from an incompatible IDataReader:")

  ' Create a table with a single integer column. Attempt
  ' to load data from a reader with a schema that is 
  ' incompatible. Note the exception, determined
  ' by the particular incompatibility:
  table = GetIntegerTable()
  reader = New DataTableReader(GetStringTable())
  Try
    table.Load(reader)
  Catch ex As Exception
    Console.WriteLine(ex.GetType.Name & ":" & ex.Message())
  End Try

  Console.WriteLine(" ============================= ")
  Console.WriteLine( _
      "Load a DataTable with an IDataReader that has extra columns:")

  ' Note that loading a reader with extra columns adds
  ' the columns to the existing table, if possible:
  table = GetIntegerTable()
  reader = New DataTableReader(GetCustomers())
  table.Load(reader)
  PrintColumns(table)

  Console.WriteLine(" ============================= ")
  Console.WriteLine( _
      "Load a DataTable with an IDataReader that has missing columns:")

  ' Note that loading a reader with missing columns causes 
  ' the columns to be filled with null data, if possible:
  table = GetCustomers()
  reader = New DataTableReader(GetIntegerTable())
  table.Load(reader)
  PrintColumns(table)

  ' Demonstrate the various possibilites when loading data into
  ' a DataTable that already contains data.
  Console.WriteLine(" ============================= ")
  Console.WriteLine("Demonstrate data considerations:")
  Console.WriteLine("Current value, Original value, (RowState)")
  Console.WriteLine(" ============================= ")
  Console.WriteLine("Original table:")

  table = SetupModifiedRows()
  DisplayRowState(table)

  Console.WriteLine(" ============================= ")
  Console.WriteLine("Data in IDataReader to be loaded:")
  DisplayRowState(GetChangedCustomers())

  PerformDemo(LoadOption.OverwriteChanges)
  PerformDemo(LoadOption.PreserveChanges)
  PerformDemo(LoadOption.Upsert)

  Console.WriteLine("Press any key to continue.")
  Console.ReadKey()
End Sub

Private Sub DisplayRowState(ByVal table As DataTable)
  For i As Integer = 0 To table.Rows.Count - 1
    Dim current As Object = "--"
    Dim original As Object = "--"
    Dim rowState As DataRowState = table.Rows(i).RowState

    ' Attempt to retrieve the current value, which doesn't exist
    ' for deleted rows:
    If rowState <> DataRowState.Deleted Then
      current = table.Rows(i)("Name", DataRowVersion.Current)
    End If

    ' Attempt to retrieve the original value, which doesn't exist
    ' for added rows:
    If rowState <> DataRowState.Added Then
      original = table.Rows(i)("Name", DataRowVersion.Original)
    End If
    Console.WriteLine("{0}: {1}, {2} ({3})", i, _
      current, original, rowState)
  Next
End Sub

Private Function GetChangedCustomers() As DataTable
  ' Create sample Customers table.
  Dim table As New DataTable

  ' Create two columns, ID and Name.
  Dim idColumn As DataColumn = table.Columns.Add("ID", _
      GetType(Integer))
  table.Columns.Add("Name", GetType(String))

  ' Set the ID column as the primary key column.
  table.PrimaryKey = New DataColumn() {idColumn}

  table.Rows.Add(New Object() {0, "XXX"})
  table.Rows.Add(New Object() {1, "XXX"})
  table.Rows.Add(New Object() {2, "XXX"})
  table.Rows.Add(New Object() {3, "XXX"})
  table.Rows.Add(New Object() {4, "XXX"})
  table.AcceptChanges()
  Return table
End Function

Private Function GetCustomers() As DataTable
  ' Create sample Customers table.
  Dim table As New DataTable

  ' Create two columns, ID and Name.
  Dim idColumn As DataColumn = table.Columns.Add("ID", _
      GetType(Integer))
  table.Columns.Add("Name", GetType(String))

  ' Set the ID column as the primary key column.
  table.PrimaryKey = New DataColumn() {idColumn}

  table.Rows.Add(New Object() {0, "Mary"})
  table.Rows.Add(New Object() {1, "Andy"})
  table.Rows.Add(New Object() {2, "Peter"})
  table.AcceptChanges()
  Return table
End Function

Private Function GetIntegerTable() As DataTable
  ' Create sample table with a single Int32 column.
  Dim table As New DataTable

  Dim idColumn As DataColumn = table.Columns.Add("ID", _
      GetType(Integer))

  ' Set the ID column as the primary key column.
  table.PrimaryKey = New DataColumn() {idColumn}

  table.Rows.Add(New Object() {4})
  table.Rows.Add(New Object() {5})
  table.AcceptChanges()
  Return table
End Function

Private Function GetStringTable() As DataTable
  ' Create sample table with a single String column.
  Dim table As New DataTable

  Dim idColumn As DataColumn = table.Columns.Add("ID", _
      GetType(String))

  ' Set the ID column as the primary key column.
  table.PrimaryKey = New DataColumn() {idColumn}

  table.Rows.Add(New Object() {"Mary"})
  table.Rows.Add(New Object() {"Andy"})
  table.Rows.Add(New Object() {"Peter"})
  table.AcceptChanges()
  Return table
End Function

Private Sub PerformDemo(ByVal optionForLoad As LoadOption)

  ' Load data into a DataTable, retrieve a DataTableReader containing
  ' different data, and call the Load method. Depending on the
  ' LoadOption value passed as a parameter, this procedure displays
  ' different results in the DataTable.
  Console.WriteLine(" ============================= ")
  Console.WriteLine("table.Load(reader, {0})", optionForLoad)
  Console.WriteLine(" ============================= ")

  Dim table As DataTable = SetupModifiedRows()
  Dim reader As New DataTableReader(GetChangedCustomers())
  AddHandler table.RowChanging, New _
      DataRowChangeEventHandler(AddressOf HandleRowChanging)

  table.Load(reader, optionForLoad)
  Console.WriteLine()
  DisplayRowState(table)
End Sub

Private Sub PrintColumns( _
   ByVal table As DataTable)

  ' Loop through all the rows in the DataTableReader.
  For Each row As DataRow In table.Rows
    For Each col As DataColumn In table.Columns
      Console.Write(row(col).ToString() & " ")
    Next
    Console.WriteLine()
  Next
End Sub

Private Function SetupModifiedRows() As DataTable
  ' Fill a DataTable with customer info, and 
  ' then modify, delete, and add rows.

  Dim table As DataTable = GetCustomers()
  ' Row 0 is unmodified.
  ' Row 1 is modified.
  ' Row 2 is deleted.
  ' Row 3 is added.
  table.Rows(1)("Name") = "Sydney"
  table.Rows(2).Delete()
  Dim row As DataRow = table.NewRow
  row("ID") = 3
  row("Name") = "Melony"
  table.Rows.Add(row)

  ' Note that the code doesn't call
  ' table.AcceptChanges()
  Return table
End Function

Private Sub HandleRowChanging(ByVal sender As Object, _
      ByVal e As System.Data.DataRowChangeEventArgs)
  Console.WriteLine( _
      "RowChanging event: ID = {0}, action = {1}", e.Row("ID"), e.Action)
End Sub

備註

該 Load 方法會從載 IDataReader入的中取出第一個結果集，並在成功完成後，將讀取器的位置設定為下一個結果集（若有的話）。在轉換資料時，該 Load 方法使用與該 Fill 方法相同的轉換規則。

Load此方法在載入實例資料IDataReader時必須考慮三個特定問題：結構、資料與事件操作。在使用該結構時， Load 方法可能會遇到如下表所述的條件。結構操作適用於所有匯入的結果集，即使沒有資料也一樣。

狀況	行為
它 DataTable 沒有架構。	該 `Load` 方法根據從匯入的 IDataReader結果集推論出該結構。
它 DataTable 有 schema，但與已載入的 schema 不相容。	該 `Load` 方法會拋出一個例外，對應於嘗試將資料載入不相容結構時所發生的特定錯誤。
這些結構是相容的，但載入的結果集結構包含不存在 `DataTable`於 .	此 `Load` 方法將額外的欄位加入 `DataTable`的結構中。若與 DataTable 載入結果集對應欄位不相容，該方法會拋出例外。該方法同時從結果集中取得所有新增欄位的限制資訊。除了主鍵限制外，此限制資訊僅在載 DataTable 入操作開始時電流中沒有任何欄位時使用。
這些結構是相容的，但載入的結果集結構包含的欄位數少於 `DataTable`。	如果缺失的欄位有預設值或欄位的資料型別是可空的，該 `Load` 方法允許新增這些列，並以預設值或空值替換缺失欄位。若無法使用預設值或 null，則 `Load` 該方法會拋出例外。若未提供特定預設值， `Load` 則以空值作為隱含的預設值。

在此方法呼叫中，指定的 LoadOption 參數會影響輸入資料的處理。 Load 方法應該如何處理與現有列主鍵相同的載入列？它應該修改目前的數值、原始數值，還是兩者都修改？這些問題以及更多，都由參數 loadOption 控制。

如果現有的列和進入的列包含對應的主鍵值，該列會使用目前的列狀態值處理，否則會被視為新一列。

在事件操作方面， RowChanging 事件發生在每列變更之前，事件 RowChanged 則在每列變更後發生。在每種情況下， Action 傳遞給事件處理器的實例屬性 DataRowChangeEventArgs 都包含與該事件相關的特定動作資訊。此動作值會依載入前該列的狀態而有所不同。在每個案例中，兩個事件都同時發生，且作用方式相同。該動作可套用於每列的當前或原始版本，或兩者皆適用，視當前列狀態而定。

下表顯示 Load 方法在每個值時 LoadOption 的行為，並展示這些值如何與被載入列的列狀態互動。最後一列（標示為「（不存在）」）描述了與任何現有列不匹配的輸入列的行為。此表中的每個儲存格描述同一列欄位的當前及原始值，以及 DataRowState 方法完成後 Load 的值。

現有 DataRowState	Upsert	覆寫變更	保留變更（預設行為）
已新增	Current = <進入> 原始 = -<不可用> 州 = <附加> RowAction = 變更	Current = <進入> 原始 = <即將抵達> 狀態 = <不變> RowAction = ChangeCurrentAndOriginal	Current = <現有> 原始 = <即將抵達> 狀態 = <修改版> RowAction = ChangeOriginal
已修改	Current = <進入> 原始 = <現存> 狀態 = <修改版> RowAction = 變更	Current = <進入> 原始 = <即將抵達> 狀態 = <不變> RowAction = ChangeCurrentAndOriginal	Current = <現有> 原始 = <即將抵達> 狀態 = <修改版> RowAction =ChangeOriginal
已刪除	（載入不會影響已刪除的列） Current = --- 原始 = <現存> 狀態 = <已刪除> （新增一列具有以下特徵） Current = <進入> 原始 = <不可取得> 州 = <附加> RowAction = 加法	還原刪除，以及 Current = <進入> 原始 = <即將抵達> 狀態 = <不變> RowAction = ChangeCurrentAndOriginal	目前 = <不可用> 原始 = <即將抵達> 狀態 = <已刪除> RowAction = ChangeOriginal
未更改	Current = <進入> 原始 = <現存> 如果新值與現有值相同，則狀態 = <不變> RowAction = 無否則狀態 = <修改版> RowAction = 變更	Current = <進入> 原始 = <即將抵達> 狀態 = <不變> RowAction = ChangeCurrentAndOriginal	Current = <進入> 原始 = <即將抵達> 狀態 = <不變> RowAction = ChangeCurrentAndOriginal
不在場）	Current = <進入> 原始 = <不可取得> 州 = <附加> RowAction = 加法	Current = <進入> 原始 = <即將抵達> 狀態 = <不變> RowAction = ChangeCurrentAndOriginal	Current = <進入> 原始 = <即將抵達> 狀態 = <不變> RowAction = ChangeCurrentAndOriginal

如果你在呼叫 Load 方法時指定 OverwriteChanges 或 PreserveChanges 選項，就會假設輸入資料來自 DataTable的主要資料來源，DataTable 會追蹤變更並能將變更傳回資料來源。若選擇 Upsert 選項，假設資料來自次級資料來源，例如由中階元件提供的資料，且可能被使用者修改。在此情況下，假設意圖是彙整來自中一個或多個資料來源 DataTable的資料，然後可能將資料傳播回主要資料來源。參數 LoadOption 用於決定用於主鍵比較的具體資料列版本。下表提供了詳細資訊。

裝載選項	用於主鍵比較的 DataRow 版本
`OverwriteChanges`	如果有原始版本，則為現行版本
`PreserveChanges`	如果有原始版本，則為現行版本
`Upsert`	如果有現行版本（若有的話）;否則為原始版本

另請參閱

適用於

Load(IDataReader, LoadOption, FillErrorEventHandler)

來源:: DataTable.cs

來源:: DataTable.cs

來源:: DataTable.cs

來源:: DataTable.cs

來源:: DataTable.cs

利用錯誤處理代理所提供的IDataReader資料，填DataTable入資料來源的值。

public:
 virtual void Load(System::Data::IDataReader ^ reader, System::Data::LoadOption loadOption, System::Data::FillErrorEventHandler ^ errorHandler);

[System.Diagnostics.CodeAnalysis.RequiresUnreferencedCode("Using LoadOption may cause members from types used in the expression column to be trimmed if not referenced directly.")]
public virtual void Load(System.Data.IDataReader reader, System.Data.LoadOption loadOption, System.Data.FillErrorEventHandler? errorHandler);

public virtual void Load(System.Data.IDataReader reader, System.Data.LoadOption loadOption, System.Data.FillErrorEventHandler? errorHandler);

public virtual void Load(System.Data.IDataReader reader, System.Data.LoadOption loadOption, System.Data.FillErrorEventHandler errorHandler);

[<System.Diagnostics.CodeAnalysis.RequiresUnreferencedCode("Using LoadOption may cause members from types used in the expression column to be trimmed if not referenced directly.")>]
abstract member Load : System.Data.IDataReader * System.Data.LoadOption * System.Data.FillErrorEventHandler -> unit
override this.Load : System.Data.IDataReader * System.Data.LoadOption * System.Data.FillErrorEventHandler -> unit

abstract member Load : System.Data.IDataReader * System.Data.LoadOption * System.Data.FillErrorEventHandler -> unit
override this.Load : System.Data.IDataReader * System.Data.LoadOption * System.Data.FillErrorEventHandler -> unit

Public Overridable Sub Load (reader As IDataReader, loadOption As LoadOption, errorHandler As FillErrorEventHandler)

參數

reader: IDataReader

IDataReader A 提供結果集。

loadOption: LoadOption

列舉中的一個值 LoadOption ，表示已在中的 DataTable 列與共用相同主鍵的入列如何結合。

errorHandler: FillErrorEventHandler

當載入資料時發生錯誤時，會呼叫一個 FillErrorEventHandler 代理。

屬性: RequiresUnreferencedCodeAttribute

範例

static void Main()
{
    // Attempt to load data from a data reader in which
    // the schema is incompatible with the current schema.
    // If you use exception handling, you won't get the chance
    // to examine each row, and each individual table,
    // as the Load method progresses.
    // By taking advantage of the FillErrorEventHandler delegate,
    // you can interact with the Load process as an error occurs,
    // attempting to fix the problem, or simply continuing or quitting
    // the Load process:
    DataTable table = GetIntegerTable();
    DataTableReader reader = new DataTableReader(GetStringTable());
    table.Load(reader, LoadOption.OverwriteChanges, FillErrorHandler);

    Console.WriteLine("Press any key to continue.");
    Console.ReadKey();
}

private static DataTable GetIntegerTable()
{
    // Create sample Customers table, in order
    // to demonstrate the behavior of the DataTableReader.
    DataTable table = new DataTable();

    // Create two columns, ID and Name.
    DataColumn idColumn = table.Columns.Add("ID", typeof(int));

    // Set the ID column as the primary key column.
    table.PrimaryKey = new DataColumn[] { idColumn };

    table.Rows.Add(new object[] { 4 });
    table.Rows.Add(new object[] { 5 });
    table.AcceptChanges();
    return table;
}

private static DataTable GetStringTable()
{
    // Create sample Customers table, in order
    // to demonstrate the behavior of the DataTableReader.
    DataTable table = new DataTable();

    // Create two columns, ID and Name.
    DataColumn idColumn = table.Columns.Add("ID", typeof(string));

    // Set the ID column as the primary key column.
    table.PrimaryKey = new DataColumn[] { idColumn };

    table.Rows.Add(new object[] { "Mary" });
    table.Rows.Add(new object[] { "Andy" });
    table.Rows.Add(new object[] { "Peter" });
    table.AcceptChanges();
    return table;
}

static void FillErrorHandler(object sender, FillErrorEventArgs e)
{
    // You can use the e.Errors value to determine exactly what
    // went wrong.
    if (e.Errors.GetType() == typeof(System.FormatException))
    {
        Console.WriteLine("Error when attempting to update the value: {0}",
            e.Values[0]);
    }

    // Setting e.Continue to True tells the Load
    // method to continue trying. Setting it to False
    // indicates that an error has occurred, and the
    // Load method raises the exception that got
    // you here.
    e.Continue = true;
}

Sub Main()
  Dim table As New DataTable()

  ' Attempt to load data from a data reader in which
  ' the schema is incompatible with the current schema.
  ' If you use exception handling, you won't get the chance
  ' to examine each row, and each individual table,
  ' as the Load method progresses.
  ' By taking advantage of the FillErrorEventHandler delegate,
  ' you can interact with the Load process as an error occurs,
  ' attempting to fix the problem, or simply continuing or quitting
  ' the Load process:
  table = GetIntegerTable()
  Dim reader As New DataTableReader(GetStringTable())
  table.Load(reader, LoadOption.OverwriteChanges, _
      AddressOf FillErrorHandler)

  Console.WriteLine("Press any key to continue.")
  Console.ReadKey()
End Sub

Private Sub FillErrorHandler(ByVal sender As Object, _
  ByVal e As FillErrorEventArgs)
  ' You can use the e.Errors value to determine exactly what
  ' went wrong.
  If e.Errors.GetType Is GetType(System.FormatException) Then
    Console.WriteLine("Error when attempting to update the value: {0}", _
      e.Values(0))
  End If

  ' Setting e.Continue to True tells the Load
  ' method to continue trying. Setting it to False
  ' indicates that an error has occurred, and the 
  ' Load method raises the exception that got 
  ' you here.
  e.Continue = True
End Sub

Private Function GetIntegerTable() As DataTable
  ' Create sample table with a single Int32 column.
  Dim table As New DataTable

  Dim idColumn As DataColumn = table.Columns.Add("ID", GetType(Integer))

  ' Set the ID column as the primary key column.
  table.PrimaryKey = New DataColumn() {idColumn}

  table.Rows.Add(New Object() {4})
  table.Rows.Add(New Object() {5})
  table.TableName = "IntegerTable"
  table.AcceptChanges()
  Return table
End Function

Private Function GetStringTable() As DataTable
  ' Create sample table with a single String column.
  Dim table As New DataTable

  Dim idColumn As DataColumn = table.Columns.Add("ID", _
      GetType(String))

  ' Set the ID column as the primary key column.
  table.PrimaryKey = New DataColumn() {idColumn}

  table.Rows.Add(New Object() {"Mary"})
  table.Rows.Add(New Object() {"Andy"})
  table.Rows.Add(New Object() {"Peter"})
  table.AcceptChanges()
  Return table
End Function

Private Sub PrintColumns( _
   ByVal table As DataTable)

  ' Loop through all the rows in the DataTableReader.
  For Each row As DataRow In table.Rows
    For Each col As DataColumn In table.Columns
      Console.Write(row(col).ToString() & " ")
    Next
    Console.WriteLine()
  Next
End Sub

備註

該 Load 方法會從載 IDataReader入的中取出第一個結果集，並在成功完成後，將讀取器的位置設定為下一個結果集（若有的話）。在轉換資料時，該 Load 方法使用與該 DbDataAdapter.Fill 方法相同的轉換規則。

狀況	行為
它 DataTable 沒有架構。	該 `Load` 方法根據從匯入的 IDataReader結果集推論出該結構。
它 DataTable 有 schema，但與已載入的 schema 不相容。	該 `Load` 方法會拋出一個例外，對應於嘗試將資料載入不相容結構時所發生的特定錯誤。
這些結構是相容的，但載入的結果集結構包含不存在 `DataTable`於 .	此 `Load` 方法將額外的欄位加入 `DataTable`的結構中。若與 DataTable 載入結果集對應欄位不相容，該方法會拋出例外。該方法同時從結果集中取得所有新增欄位的限制資訊。除了主鍵限制外，此限制資訊僅在載 DataTable 入操作開始時電流中沒有任何欄位時使用。
這些結構是相容的，但載入的結果集結構包含的欄位數少於 `DataTable`。	如果缺失的欄位有預設值或欄位的資料型別是可空的，該 `Load` 方法允許新增這些列，並以預設值或空值替換缺失欄位。若無法使用預設值或 null，則 `Load` 該方法會拋出例外。若未提供特定預設值， `Load` 則以空值作為隱含的預設值。

如果現有的列和進入的列包含對應的主鍵值，該列會使用目前的列狀態值處理，否則會被視為新一列。

現有 DataRowState	Upsert	覆寫變更	保留變更（預設行為）
已新增	Current = <進入> 原始 = -<不可用> 州 = <附加> RowAction = 變更	Current = <進入> 原始 = <即將抵達> 狀態 = <不變> RowAction = ChangeCurrentAndOriginal	Current = <現有> 原始 = <即將抵達> 狀態 = <修改版> RowAction = ChangeOriginal
已修改	Current = <進入> 原始 = <現存> 狀態 = <修改版> RowAction = 變更	Current = <進入> 原始 = <即將抵達> 狀態 = <不變> RowAction = ChangeCurrentAndOriginal	Current = <現有> 原始 = <即將抵達> 狀態 = <修改版> RowAction =ChangeOriginal
被 eleted	（載入不會影響已刪除的列） Current = --- 原始 = <現存> 狀態 = <已刪除> （新增一列具有以下特徵） Current = <進入> 原始 = <不可取得> 州 = <附加> RowAction = 加法	還原刪除，以及 Current = <進入> 原始 = <即將抵達> 狀態 = <不變> RowAction = ChangeCurrentAndOriginal	目前 = <不可用> 原始 = <即將抵達> 狀態 = <已刪除> RowAction = ChangeOriginal
未更改	Current = <進入> 原始 = <現存> 如果新值與現有值相同，則狀態 = <不變> RowAction = 無否則狀態 = <修改版> RowAction = 變更	Current = <進入> 原始 = <即將抵達> 狀態 = <不變> RowAction = ChangeCurrentAndOriginal	Current = <進入> 原始 = <即將抵達> 狀態 = <不變> RowAction = ChangeCurrentAndOriginal
不在場）	Current = <進入> 原始 = <不可取得> 州 = <附加> RowAction = 加法	Current = <進入> 原始 = <即將抵達> 狀態 = <不變> RowAction = ChangeCurrentAndOriginal	Current = <進入> 原始 = <即將抵達> 狀態 = <不變> RowAction = ChangeCurrentAndOriginal

裝載選項	用於主鍵比較的 DataRow 版本
`OverwriteChanges`	如果有原始版本，則為現行版本
`PreserveChanges`	如果有原始版本，則為現行版本
`Upsert`	如果有現行版本（若有的話）;否則為原始版本

參數 errorHandler 是一個 FillErrorEventHandler 代理，指的是載入資料時發生錯誤時所呼叫的程序。 FillErrorEventArgs傳遞給程序的參數提供了屬性，讓你能取得關於發生錯誤、當前資料列以及被填入的資料DataTable資訊。使用這種代理機制，而非較簡單的嘗試/接球區塊，能讓你判斷錯誤、處理情況，並繼續處理。參數 FillErrorEventArgs 提供一個 Continue 屬性：將此屬性設為表示 true 你已處理錯誤並希望繼續處理。將屬性設為， false 表示你希望停止處理。請注意，將屬性設為會 false 觸發問題的程式碼拋出例外。

另請參閱

適用於

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共用方式為

DataTable.Load 方法

定義

多載

範例

備註

Load(IDataReader)

參數

範例

備註

另請參閱

適用於

Load(IDataReader, LoadOption)

參數

範例

備註

另請參閱

適用於

Load(IDataReader, LoadOption, FillErrorEventHandler)

參數

範例

備註

另請參閱

適用於

意見反應