DataTable.Merge 方法

定义

命名空间:: System.Data

程序集:: netstandard.dll, System.Data.Common.dll

程序集:: System.Data.Common.dll

程序集:: System.Data.dll

程序集:: netstandard.dll

重要

一些信息与预发行产品相关，相应产品在发行之前可能会进行重大修改。对于此处提供的信息，Microsoft 不作任何明示或暗示的担保。

将指定的 DataTable 值与当前 DataTable合并。

重载

名称	说明
Merge(DataTable, Boolean, MissingSchemaAction)	将指定的 DataTable 项与当前 `DataTable`合并，指示是否保留更改以及如何处理当前 `DataTable`中缺少的架构。
Merge(DataTable, Boolean)	将指定的 DataTable 值与当前 `DataTable`合并，指示是否保留当前 `DataTable`更改。
Merge(DataTable)	将指定的 DataTable 值与当前 DataTable合并。

示例

以下控制台应用程序演示了方法参数missingSchemaAction的行为Merge。此示例创建同一表的两个版本，修改第二个版本的架构。然后，代码尝试将第二个表合并到第一个表。

注释

此示例演示如何使用合并的重载版本之一。有关可能提供的其他示例，请参阅各个重载主题。

private static void DemonstrateMergeTable()
{
    DataTable table1 = new DataTable("Items");

    // Add columns
    DataColumn idColumn = new DataColumn("id", typeof(System.Int32));
    DataColumn itemColumn = new DataColumn("item", typeof(System.Int32));
    table1.Columns.Add(idColumn);
    table1.Columns.Add(itemColumn);

    // Set the primary key column.
    table1.PrimaryKey = new DataColumn[] { idColumn };

    // Add RowChanged event handler for the table.
    table1.RowChanged += new
        System.Data.DataRowChangeEventHandler(Row_Changed);

    // Add ten rows.
    DataRow row;
    for (int i = 0; i <= 9; i++)
    {
        row = table1.NewRow();
        row["id"] = i;
        row["item"] = i;
        table1.Rows.Add(row);
    }

    // Accept changes.
    table1.AcceptChanges();
    PrintValues(table1, "Original values");

    // Create a second DataTable identical to the first.
    DataTable table2 = table1.Clone();

    // Add column to the second column, so that the
    // schemas no longer match.
    table2.Columns.Add("newColumn", typeof(System.String));

    // Add three rows. Note that the id column can't be the
    // same as existing rows in the original table.
    row = table2.NewRow();
    row["id"] = 14;
    row["item"] = 774;
    row["newColumn"] = "new column 1";
    table2.Rows.Add(row);

    row = table2.NewRow();
    row["id"] = 12;
    row["item"] = 555;
    row["newColumn"] = "new column 2";
    table2.Rows.Add(row);

    row = table2.NewRow();
    row["id"] = 13;
    row["item"] = 665;
    row["newColumn"] = "new column 3";
    table2.Rows.Add(row);

    // Merge table2 into the table1.
    Console.WriteLine("Merging");
    table1.Merge(table2, false, MissingSchemaAction.Add);
    PrintValues(table1, "Merged With table1, schema added");
}

private static void Row_Changed(object sender,
    DataRowChangeEventArgs e)
{
    Console.WriteLine("Row changed {0}\t{1}", e.Action,
        e.Row.ItemArray[0]);
}

private static void PrintValues(DataTable table, string label)
{
    // Display the values in the supplied DataTable:
    Console.WriteLine(label);
    foreach (DataRow row in table.Rows)
    {
        foreach (DataColumn col in table.Columns)
        {
            Console.Write("\t " + row[col].ToString());
        }
        Console.WriteLine();
    }
}

Private Sub DemonstrateMergeTable()
  Dim table1 As New DataTable("Items")

  ' Add columns
  Dim idColumn As New DataColumn("id", GetType(System.Int32))
  Dim itemColumn As New DataColumn("item", GetType(System.Int32))
  table1.Columns.Add(idColumn)
  table1.Columns.Add(itemColumn)

  ' Set the primary key column.
  table1.PrimaryKey = New DataColumn() {idColumn}

  ' Add RowChanged event handler for the table.
  AddHandler table1.RowChanged, AddressOf Row_Changed

  ' Add some rows.
  Dim row As DataRow
  For i As Integer = 0 To 3
    row = table1.NewRow()
    row("id") = i
    row("item") = i
    table1.Rows.Add(row)
  Next i

  ' Accept changes.
  table1.AcceptChanges()
  PrintValues(table1, "Original values")

  ' Create a second DataTable identical to the first.
  Dim table2 As DataTable = table1.Clone()

  ' Add column to the second column, so that the 
  ' schemas no longer match.
  table2.Columns.Add("newColumn", GetType(System.String))

  ' Add three rows. Note that the id column can't be the 
  ' same as existing rows in the original table.
  row = table2.NewRow()
  row("id") = 14
  row("item") = 774
  row("newColumn") = "new column 1"
  table2.Rows.Add(row)

  row = table2.NewRow()
  row("id") = 12
  row("item") = 555
  row("newColumn") = "new column 2"
  table2.Rows.Add(row)

  row = table2.NewRow()
  row("id") = 13
  row("item") = 665
  row("newColumn") = "new column 3"
  table2.Rows.Add(row)

  ' Merge table2 into the table1.
  Console.WriteLine("Merging")
  table1.Merge(table2, False, MissingSchemaAction.Add)
  PrintValues(table1, "Merged With table1, Schema added")
End Sub

Private Sub Row_Changed(ByVal sender As Object, _
      ByVal e As DataRowChangeEventArgs)
  Console.WriteLine("Row changed {0}{1}{2}", _
    e.Action, ControlChars.Tab, e.Row.ItemArray(0))
End Sub

Private Sub PrintValues(ByVal table As DataTable, _
      ByVal label As String)
  ' Display the values in the supplied DataTable:
  Console.WriteLine(label)
  For Each row As DataRow In table.Rows
    For Each col As DataColumn In table.Columns
      Console.Write(ControlChars.Tab + " " + row(col).ToString())
    Next col
    Console.WriteLine()
  Next row
End Sub

注解

该方法 Merge 用于合并两 DataTable 个具有基本相似架构的对象。合并通常用于客户端应用程序，以将数据源的最新更改合并到现有 DataTable数据源中。这样，客户端应用程序就可以使用数据源中的最新数据进行刷新 DataTable 。

合并操作只考虑原始表和要合并的表。子表不受影响或包含。如果表具有一个或多个子表（定义为关系的一部分），则必须单独合并每个子表。

Merge(DataTable, Boolean, MissingSchemaAction)

Source:: DataTable.cs

Source:: DataTable.cs

Source:: DataTable.cs

Source:: DataTable.cs

Source:: DataTable.cs

将指定的 DataTable 项与当前 DataTable合并，指示是否保留更改以及如何处理当前 DataTable中缺少的架构。

public:
 void Merge(System::Data::DataTable ^ table, bool preserveChanges, System::Data::MissingSchemaAction missingSchemaAction);

public void Merge(System.Data.DataTable table, bool preserveChanges, System.Data.MissingSchemaAction missingSchemaAction);

member this.Merge : System.Data.DataTable * bool * System.Data.MissingSchemaAction -> unit

Public Sub Merge (table As DataTable, preserveChanges As Boolean, missingSchemaAction As MissingSchemaAction)

参数

table: DataTable

要 DataTable 与当前 DataTable合并的。

preserveChanges: Boolean

如果保留当前更改，则为。

missingSchemaAction: MissingSchemaAction

其中一个 MissingSchemaAction 值。

示例

private static void DemonstrateMergeTable()
{
    DataTable itemsTable = new DataTable("Items");

    // Add columns
    DataColumn idColumn = new DataColumn("id", typeof(System.Int32));
    DataColumn itemColumn = new DataColumn("item", typeof(System.Int32));
    itemsTable.Columns.Add(idColumn);
    itemsTable.Columns.Add(itemColumn);

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

    // Add RowChanged event handler for the table.
    itemsTable.RowChanged +=
        new System.Data.DataRowChangeEventHandler(Row_Changed);

    // Add ten rows.
    DataRow row;
    for (int i = 0; i <= 9; i++)
    {
        row = itemsTable.NewRow();
        row["id"] = i;
        row["item"] = i;
        itemsTable.Rows.Add(row);
    }

    // Accept changes.
    itemsTable.AcceptChanges();
    PrintValues(itemsTable, "Original values");

    // Create a second DataTable identical to the first.
    DataTable itemsClone = itemsTable.Clone();

    // Add column to the second column, so that the
    // schemas no longer match.
    itemsClone.Columns.Add("newColumn", typeof(System.String));

    // Add three rows. Note that the id column can't be the
    // same as existing rows in the original table.
    row = itemsClone.NewRow();
    row["id"] = 14;
    row["item"] = 774;
    row["newColumn"] = "new column 1";
    itemsClone.Rows.Add(row);

    row = itemsClone.NewRow();
    row["id"] = 12;
    row["item"] = 555;
    row["newColumn"] = "new column 2";
    itemsClone.Rows.Add(row);

    row = itemsClone.NewRow();
    row["id"] = 13;
    row["item"] = 665;
    row["newColumn"] = "new column 3";
    itemsClone.Rows.Add(row);

    // Merge itemsClone into the itemsTable.
    Console.WriteLine("Merging");
    itemsTable.Merge(itemsClone, false, MissingSchemaAction.Add);
    PrintValues(itemsTable, "Merged With itemsTable, schema added");
}

private static void Row_Changed(object sender,
    DataRowChangeEventArgs e)
{
    Console.WriteLine("Row changed {0}\t{1}",
        e.Action, e.Row.ItemArray[0]);
}

private static void PrintValues(DataTable table, string label)
{
    // Display the values in the supplied DataTable:
    Console.WriteLine(label);
    foreach (DataRow row in table.Rows)
    {
        foreach (DataColumn col in table.Columns)
        {
            Console.Write("\t " + row[col].ToString());
        }
        Console.WriteLine();
    }
}

Private Sub DemonstrateMergeTable()
  Dim itemsTable As New DataTable("Items")

  ' Add columns
  Dim idColumn As New DataColumn("id", GetType(System.Int32))
  Dim itemColumn As New DataColumn("item", GetType(System.Int32))
  itemsTable.Columns.Add(idColumn)
  itemsTable.Columns.Add(itemColumn)

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

  ' Add RowChanged event handler for the table.
  AddHandler itemsTable.RowChanged, AddressOf Row_Changed

  ' Add some rows.
  Dim row As DataRow
  For i As Integer = 0 To 3
    row = itemsTable.NewRow()
    row("id") = i
    row("item") = i
    itemsTable.Rows.Add(row)
  Next i

  ' Accept changes.
  itemsTable.AcceptChanges()
  PrintValues(itemsTable, "Original values")

  ' Create a second DataTable identical to the first.
  Dim itemsClone As DataTable = itemsTable.Clone()

  ' Add column to the second column, so that the 
  ' schemas no longer match.
  itemsClone.Columns.Add("newColumn", GetType(System.String))

  ' Add three rows. Note that the id column can't be the 
  ' same as existing rows in the original table.
  row = itemsClone.NewRow()
  row("id") = 14
  row("item") = 774
  row("newColumn") = "new column 1"
  itemsClone.Rows.Add(row)

  row = itemsClone.NewRow()
  row("id") = 12
  row("item") = 555
  row("newColumn") = "new column 2"
  itemsClone.Rows.Add(row)

  row = itemsClone.NewRow()
  row("id") = 13
  row("item") = 665
  row("newColumn") = "new column 3"
  itemsClone.Rows.Add(row)

  ' Merge itemsClone into the itemsTable.
  Console.WriteLine("Merging")
  itemsTable.Merge(itemsClone, False, MissingSchemaAction.Add)
  PrintValues(itemsTable, "Merged With itemsTable, Schema added")
End Sub

Private Sub Row_Changed(ByVal sender As Object, _
  ByVal e As DataRowChangeEventArgs)
  Console.WriteLine("Row changed {0}{1}{2}", _
    e.Action, ControlChars.Tab, e.Row.ItemArray(0))
End Sub

Private Sub PrintValues(ByVal table As DataTable, ByVal label As String)
  ' Display the values in the supplied DataTable:
  Console.WriteLine(label)
  For Each row As DataRow In table.Rows
    For Each col As DataColumn In table.Columns
      Console.Write(ControlChars.Tab + " " + row(col).ToString())
    Next col
    Console.WriteLine()
  Next row
End Sub

注解

合并操作只考虑原始表和要合并的表。子表不受影响或包含。如果表具有一个或多个子表（定义为关系的一部分），则必须单独合并每个子表。

该方法 Merge 通常在一系列过程结束时调用，这些过程涉及验证更改、协调错误、使用更改更新数据源，最后刷新现有 DataTable内容。

执行合并时，除非开发人员为 preserveChanges 参数指定 false，否则在合并操作期间保留合并之前对现有数据所做的更改。如果参数 preserveChanges 设置为 true，则传入值不会覆盖现有行的当前行版本中的现有值。如果参数 preserveChanges 设置为 false，则传入值将覆盖现有行的当前行版本中的现有值。有关行版本的详细信息，请参阅行状态和行版本。

在客户端应用程序中，通常有一个按钮，用户可以单击该按钮来收集已更改的数据，并在将其发送回中间层组件之前对其进行验证。在此方案中， GetChanges 首先调用该方法。此方法返回第二 DataTable 个针对验证和合并的优化方法。第二 DataTable 个对象仅 DataTable 包含已更改的对象， DataRow 从而导致原始 DataTable对象的子集。此子集通常较小，因此此子集更高效地传回中间层组件。中间层组件随后通过存储过程更新原始数据源。然后，中间层可以发送回 DataTable 包含原始数据和数据源的最新数据的新数据（再次运行原始查询），也可以发送回子集，其中包含从数据源对它所做的任何更改。（例如，如果数据源自动创建唯一的主键值，则可以将这些值传播回客户端应用程序。在任一情况下，都可以使用DataTable该方法将返回的DataTable返回内容合并回客户端应用程序的原始Merge应用程序中。

Merge调用该方法时，将比较两DataTable个对象的架构，因为架构可能已更改。例如，在企业到企业方案中，自动化过程可能已将新列添加到 XML 架构。如果源 DataTable 包含目标中缺少的架构元素（已添加 DataColumn 的对象），则可以通过将参数设置为 missingSchemaActionMissingSchemaAction.Add 将架构元素添加到目标。在这种情况下，合并 DataTable 包含添加的架构和数据。

合并架构后，数据将合并。

将新源DataTable合并到目标时，具有DataRowState值UnchangedModified或Deleted与具有相同主键值的目标行匹配的任何源行。值为 DataRowState 的 Added 源行与与新源行相同的主键值与新的目标行匹配。

另请参阅

适用于

Merge(DataTable, Boolean)

Source:: DataTable.cs

Source:: DataTable.cs

Source:: DataTable.cs

Source:: DataTable.cs

Source:: DataTable.cs

将指定的 DataTable 值与当前 DataTable合并，指示是否保留当前 DataTable更改。

public:
 void Merge(System::Data::DataTable ^ table, bool preserveChanges);

public void Merge(System.Data.DataTable table, bool preserveChanges);

member this.Merge : System.Data.DataTable * bool -> unit

Public Sub Merge (table As DataTable, preserveChanges As Boolean)

参数

table: DataTable

要 DataTable 与当前 DataTable合并的。

preserveChanges: Boolean

如果保留当前更改，则为。

示例

以下控制台应用程序创建包含 DataTable 的行，修改这些行中的某些数据，并尝试合并其他 DataTable行中的数据。该示例演示参数的不同行为 preserveChanges 。


private static void DemonstrateMergeTable()
{
    // Demonstrate merging, within and without
    // preserving changes.

    // In this example, take these actions:
    // 1. Create a DataTable (table1) and fill the table with data.
    // 2. Create a copy of table1, and modify its data (modifiedTable).
    // 3. Modify data in table1.
    // 4. Make a copy of table1 (table1Copy).
    // 5. Merge the data from modifiedTable into table1 and table1Copy,
    //    showing the difference between setting the preserveChanges
    //    parameter to true and false.

    // Create a new DataTable.
    DataTable table1 = new DataTable("Items");

    // Add two columns to the table:
    DataColumn column = new DataColumn("id", typeof(System.Int32));
    column.AutoIncrement = true;
    table1.Columns.Add(column);

    column = new DataColumn("item", typeof(System.String));
    table1.Columns.Add(column);

    // Set primary key column.
    table1.PrimaryKey = new DataColumn[] { table1.Columns[0] };

    // Add some rows.
    DataRow row;
    for (int i = 0; i <= 3; i++)
    {
        row = table1.NewRow();
        row["item"] = "Item " + i;
        table1.Rows.Add(row);
    }

    // Accept changes.
    table1.AcceptChanges();
    PrintValues(table1, "Original values");

    // Using the same schema as the original table,
    // modify the data for later merge.
    DataTable modifiedTable = table1.Copy();
    foreach (DataRow rowModified in modifiedTable.Rows)
    {
        rowModified["item"] = rowModified["item"].ToString()
            + " modified";
    }
    modifiedTable.AcceptChanges();

    // Change row values, and add a new row:
    table1.Rows[0]["item"] = "new Item 0";
    table1.Rows[1]["item"] = "new Item 1";

    row = table1.NewRow();
    row["id"] = 4;
    row["item"] = "Item 4";
    table1.Rows.Add(row);

    // Get a copy of the modified data:
    DataTable table1Copy = table1.Copy();
    PrintValues(table1, "Modified and new Values");
    PrintValues(modifiedTable, "Data to be merged into table1");

    // Merge new data into the modified data.
    table1.Merge(modifiedTable, true);
    PrintValues(table1, "Merged data (preserve changes)");

    table1Copy.Merge(modifiedTable, false);
    PrintValues(table1Copy, "Merged data (don't preserve changes)");
}

private static void PrintValues(DataTable table, string label)
{
    // Display the values in the supplied DataTable:
    Console.WriteLine(label);
    foreach (DataRow row in table.Rows)
    {
        foreach (DataColumn column in table.Columns)
        {
            Console.Write("\t{0}", row[column, DataRowVersion.Current]);
        }
        Console.WriteLine();
    }
}

Private Sub DemonstrateMergeTable()
  ' Demonstrate merging, within and without
  ' preserving changes.

  ' In this example, take these actions:
  ' 1. Create a DataTable (table1) and fill the table with data.
  ' 2. Create a copy of table1, and modify its data (modifiedTable).
  ' 3. Modify data in table1.
  ' 4. Make a copy of table1 (table1Copy).
  ' 5. Merge the data from modifiedTable into table1 and table1Copy, 
  '    showing the difference between setting the preserveChanges 
  '    parameter to true and false.

  ' Create a new DataTable.
  Dim table1 As New DataTable("Items")

  ' Add two columns to the table:
  Dim column As New DataColumn("id", GetType(System.Int32))
  column.AutoIncrement = True
  table1.Columns.Add(column)

  column = New DataColumn("item", GetType(System.String))
  table1.Columns.Add(column)

  ' Set primary key column.
  table1.PrimaryKey = New DataColumn() {table1.Columns(0)}

  ' Add some rows.
  Dim row As DataRow
  For i As Integer = 0 To 3
    row = table1.NewRow()
    row("item") = "Item " & i
    table1.Rows.Add(row)
  Next i

  ' Accept changes.
  table1.AcceptChanges()
  PrintValues(table1, "Original values")

  ' Using the same schema as the original table, 
  ' modify the data for later merge.
  Dim modifiedTable As DataTable = table1.Copy()
  For Each row In modifiedTable.Rows
    row("item") = row("item").ToString() & " modified"
  Next
  modifiedTable.AcceptChanges()

  ' Change row values, and add a new row:
  table1.Rows(0)("item") = "New Item 0"
  table1.Rows(1)("item") = "New Item 1"

  row = table1.NewRow()
  row("id") = 4
  row("item") = "Item 4"
  table1.Rows.Add(row)

  ' Get a copy of the modified data:
  Dim table1Copy As DataTable = table1.Copy()
  PrintValues(table1, "Modified and New Values")
  PrintValues(modifiedTable, "Data to be merged into table1")


  ' Merge new data into the modified data.
  table1.Merge(modifiedTable, True)
  PrintValues(table1, "Merged data (preserve changes)")

  table1Copy.Merge(modifiedTable, False)
  PrintValues(table1Copy, "Merged data (don't preserve changes)")

End Sub

Private Sub PrintValues(ByVal table As DataTable, _
  ByVal label As String)

  ' Display the values in the supplied DataTable:
  Console.WriteLine(label)
  For Each row As DataRow In table.Rows
    For Each column As DataColumn In table.Columns
      Console.Write("{0}{1}", ControlChars.Tab, row(column, _
          DataRowVersion.Current))
    Next column
    Console.WriteLine()
  Next row
End Sub

注解

Merge 方法用于合并两 DataTable 个具有基本相似架构的对象。合并通常用于客户端应用程序，以将数据源的最新更改合并到现有 DataTable数据源中。这样，客户端应用程序就可以使用数据源中的最新数据进行刷新 DataTable 。

合并操作只考虑原始表和要合并的表。子表不受影响或包含。如果表具有一个或多个子表（定义为关系的一部分），则必须单独合并每个子表。

该方法 Merge 通常在一系列过程结束时调用，这些过程涉及验证更改、协调错误、使用更改更新数据源，最后刷新现有 DataTable内容。

另请参阅

适用于

Merge(DataTable)

Source:: DataTable.cs

Source:: DataTable.cs

Source:: DataTable.cs

Source:: DataTable.cs

Source:: DataTable.cs

将指定的 DataTable 值与当前 DataTable合并。

public:
 void Merge(System::Data::DataTable ^ table);

public void Merge(System.Data.DataTable table);

member this.Merge : System.Data.DataTable -> unit

Public Sub Merge (table As DataTable)

参数

table: DataTable

要 DataTable 与当前 DataTable合并的。

示例

以下控制台应用程序创建一个简单的 DataTable 数据，并将数据添加到表中。然后，该示例创建表的副本，并将行添加到副本。最后，该示例调用 Merge 该方法将第二个表中的数据与第一个表中的数据合并。

private static void DemonstrateMergeTable()
{
    DataTable table1 = new DataTable("Items");

    // Add columns
    DataColumn column1 = new DataColumn("id", typeof(System.Int32));
    DataColumn column2 = new DataColumn("item", typeof(System.Int32));
    table1.Columns.Add(column1);
    table1.Columns.Add(column2);

    // Set the primary key column.
    table1.PrimaryKey = new DataColumn[] { column1 };

    // Add RowChanged event handler for the table.
    table1.RowChanged +=
        new System.Data.DataRowChangeEventHandler(Row_Changed);

    // Add some rows.
    DataRow row;
    for (int i = 0; i <= 3; i++)
    {
        row = table1.NewRow();
        row["id"] = i;
        row["item"] = i;
        table1.Rows.Add(row);
    }

    // Accept changes.
    table1.AcceptChanges();
    PrintValues(table1, "Original values");

    // Create a second DataTable identical to the first.
    DataTable table2 = table1.Clone();

    // Add three rows. Note that the id column can't be the
    // same as existing rows in the original table.
    row = table2.NewRow();
    row["id"] = 14;
    row["item"] = 774;
    table2.Rows.Add(row);

    row = table2.NewRow();
    row["id"] = 12;
    row["item"] = 555;
    table2.Rows.Add(row);

    row = table2.NewRow();
    row["id"] = 13;
    row["item"] = 665;
    table2.Rows.Add(row);

    // Merge table2 into the table1.
    Console.WriteLine("Merging");
    table1.Merge(table2);
    PrintValues(table1, "Merged With table1");
}

private static void Row_Changed(object sender,
    DataRowChangeEventArgs e)
{
    Console.WriteLine("Row changed {0}\t{1}",
        e.Action, e.Row.ItemArray[0]);
}

private static void PrintValues(DataTable table, string label)
{
    // Display the values in the supplied DataTable:
    Console.WriteLine(label);
    foreach (DataRow row in table.Rows)
    {
        foreach (DataColumn col in table.Columns)
        {
            Console.Write("\t " + row[col].ToString());
        }
        Console.WriteLine();
    }
}

Private Sub DemonstrateMergeTable()
  Dim table1 As New DataTable("Items")

  ' Add columns
  Dim column1 As New DataColumn("id", GetType(System.Int32))
  Dim column2 As New DataColumn("item", GetType(System.Int32))
  table1.Columns.Add(column1)
  table1.Columns.Add(column2)

  ' Set the primary key column.
  table1.PrimaryKey = New DataColumn() {column1}

  ' Add RowChanged event handler for the table.
  AddHandler table1.RowChanged, AddressOf Row_Changed

  ' Add some rows.
  Dim row As DataRow
  For i As Integer = 0 To 3
    row = table1.NewRow()
    row("id") = i
    row("item") = i
    table1.Rows.Add(row)
  Next i

  ' Accept changes.
  table1.AcceptChanges()
  PrintValues(table1, "Original values")

  ' Create a second DataTable identical to the first.
  Dim table2 As DataTable = table1.Clone()

  ' Add three rows. Note that the id column can't be the 
  ' same as existing rows in the original table.
  row = table2.NewRow()
  row("id") = 14
  row("item") = 774
  table2.Rows.Add(row)

  row = table2.NewRow()
  row("id") = 12
  row("item") = 555
  table2.Rows.Add(row)

  row = table2.NewRow()
  row("id") = 13
  row("item") = 665
  table2.Rows.Add(row)

  ' Merge table2 into the table1.
  Console.WriteLine("Merging")
  table1.Merge(table2)
  PrintValues(table1, "Merged With table1")

End Sub

Private Sub Row_Changed(ByVal sender As Object, _
  ByVal e As DataRowChangeEventArgs)
  Console.WriteLine("Row changed {0}{1}{2}", _
    e.Action, ControlChars.Tab, e.Row.ItemArray(0))
End Sub

Private Sub PrintValues(ByVal table As DataTable, _
  ByVal label As String)
  ' Display the values in the supplied DataTable:
  Console.WriteLine(label)
  For Each row As DataRow In table.Rows
    For Each col As DataColumn In table.Columns
      Console.Write(ControlChars.Tab + " " + row(col).ToString())
    Next col
    Console.WriteLine()
  Next row
End Sub

注解

合并操作只考虑原始表和要合并的表。子表不受影响或包含。如果表具有一个或多个子表（定义为关系的一部分），则必须单独合并每个子表。

该方法 Merge 通常在一系列过程结束时调用，这些过程涉及验证更改、协调错误、使用更改更新数据源，最后刷新现有 DataTable内容。

执行合并时，在合并操作期间默认保留合并之前对现有数据所做的更改。开发人员可以通过为此方法调用另外两个重载之一并指定参数的 false 值 preserveChanges 来修改此行为。

在客户端应用程序中，通常有一个按钮，用户可以单击该按钮来收集已更改的数据，并在将其发送回中间层组件之前对其进行验证。在此方案中， GetChanges 首先调用该方法。此方法返回第二 DataTable 个针对验证和合并的优化方法。第二 DataTable 个对象仅 DataRow 包含已更改的对象，从而导致原始 DataTable对象的子集。此子集通常更小，因此更高效地传回中间层组件。中间层组件随后通过存储过程更新原始数据源。然后，中间层可以发送回 DataTable 包含原始数据和数据源的最新数据的新数据（再次运行原始查询），也可以发送回子集，其中包含从数据源对它所做的任何更改。（例如，如果数据源自动创建唯一的主键值，则可以将这些值传播回客户端应用程序。在任一情况下，都可以使用DataTable该方法将返回的DataTable返回内容合并回客户端应用程序的原始Merge应用程序中。

将新源DataTable合并到目标中时，任何值DataRowState为Unchanged或ModifiedDeleted与具有相同主键值的源行匹配。值为 DataRowState 的 Added 源行与与新源行相同的主键值与新的目标行匹配。

另请参阅

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