System.Data.DataTable 類別
本文提供此 API 參考文件的補充備註。
類別 DataTable 是 ADO.NET 連結庫中的中央物件。 使用 DataTable 其他物件包括 DataSet 與 DataView。
DataTable 物件名稱會有條件地區分大小寫。 例如，如果其中一個 DataTable 名稱為 「mydatatable」，而另一個名為 「Mydatatable」，則用來搜尋其中一個數據表的字串會被視為區分大小寫。 不過，如果 「mydatatable」 存在且 「Mydatatable」 不存在，則搜尋字串會視為不區分大小寫。 DataSet可以包含兩個DataTable具有相同TableName屬性值但不同Namespace屬性值的物件。 如需使用 DataTable 對象的詳細資訊，請參閱 建立DataTable。
如果您要以程式設計方式建立 DataTable ，您必須先將 物件新增 DataColumn 至 DataColumnCollection （透過 Columns 屬性存取） 來定義其架構。 如需新增 DataColumn 對象的詳細資訊，請參閱 將數據行加入DataTable。
若要將資料列加入 至 DataTable，您必須先使用 NewRow 方法傳回新的 DataRow 物件。 方法會 NewRow 傳回具有 架構的數據 DataTable列，因為它是由數據表 的 DataColumnCollection所定義。 可以儲存的數據列 DataTable 數目上限為 16,777,216。 如需詳細資訊，請參閱 將數據新增至 DataTable。
DataTable也包含物件的集合Constraint，可用來確保數據的完整性。 如需詳細資訊，請參閱 DataTable 條件約束。
有許多 DataTable 事件可用來判斷數據表何時進行變更。 其中包括 RowChanged、RowChanging、RowDeleting 和 RowDeleted。 如需可以搭配 DataTable使用之事件的詳細資訊，請參閱 處理 DataTable 事件。
建立 的實例 DataTable 時，某些讀取/寫入屬性會設定為初始值。 如需這些值的清單，請參閱建構函式 DataTable 。
注意
DataSet和 DataTable 物件繼承自 MarshalByValueComponent ，並支援 ISerializable .NET 遠端的介面。 這些是您唯一可用於 .NET 遠端處理 ADO.NET 物件。
安全性考量
如需 DataSet 和 DataTable 安全性的相關信息，請參閱 安全性指引。
範例
此範例示範如何使用特定架構定義手動建立 DataTable：
- 建立多個 DataTable 並定義初始數據行。
- 建立數據表條件約束。
- 插入值並顯示數據表。
- 建立表達式數據行並顯示數據表。
using System;
using System.Data;
class Program
{
static void Main(string[] args)
{
// Create two tables and add them into the DataSet
DataTable orderTable = CreateOrderTable();
DataTable orderDetailTable = CreateOrderDetailTable();
DataSet salesSet = new DataSet();
salesSet.Tables.Add(orderTable);
salesSet.Tables.Add(orderDetailTable);
// Set the relations between the tables and create the related constraint.
salesSet.Relations.Add("OrderOrderDetail", orderTable.Columns["OrderId"], orderDetailTable.Columns["OrderId"], true);
Console.WriteLine("After creating the foreign key constriant, you will see the following error if inserting order detail with the wrong OrderId: ");
try
{
DataRow errorRow = orderDetailTable.NewRow();
errorRow[0] = 1;
errorRow[1] = "O0007";
orderDetailTable.Rows.Add(errorRow);
}
catch (Exception e)
{
Console.WriteLine(e.Message);
}
Console.WriteLine();
// Insert the rows into the table
InsertOrders(orderTable);
InsertOrderDetails(orderDetailTable);
Console.WriteLine("The initial Order table.");
ShowTable(orderTable);
Console.WriteLine("The OrderDetail table.");
ShowTable(orderDetailTable);
// Use the Aggregate-Sum on the child table column to get the result.
DataColumn colSub = new DataColumn("SubTotal", typeof(Decimal), "Sum(Child.LineTotal)");
orderTable.Columns.Add(colSub);
// Compute the tax by referencing the SubTotal expression column.
DataColumn colTax = new DataColumn("Tax", typeof(Decimal), "SubTotal*0.1");
orderTable.Columns.Add(colTax);
// If the OrderId is 'Total', compute the due on all orders; or compute the due on this order.
DataColumn colTotal = new DataColumn("TotalDue", typeof(Decimal), "IIF(OrderId='Total',Sum(SubTotal)+Sum(Tax),SubTotal+Tax)");
orderTable.Columns.Add(colTotal);
DataRow row = orderTable.NewRow();
row["OrderId"] = "Total";
orderTable.Rows.Add(row);
Console.WriteLine("The Order table with the expression columns.");
ShowTable(orderTable);
Console.WriteLine("Press any key to exit.....");
Console.ReadKey();
}
private static DataTable CreateOrderTable()
{
DataTable orderTable = new DataTable("Order");
// Define one column.
DataColumn colId = new DataColumn("OrderId", typeof(String));
orderTable.Columns.Add(colId);
DataColumn colDate = new DataColumn("OrderDate", typeof(DateTime));
orderTable.Columns.Add(colDate);
// Set the OrderId column as the primary key.
orderTable.PrimaryKey = new DataColumn[] { colId };
return orderTable;
}
private static DataTable CreateOrderDetailTable()
{
DataTable orderDetailTable = new DataTable("OrderDetail");
// Define all the columns once.
DataColumn[] cols =
{
new DataColumn("OrderDetailId", typeof(Int32)),
new DataColumn("OrderId", typeof(String)),
new DataColumn("Product", typeof(String)),
new DataColumn("UnitPrice", typeof(Decimal)),
new DataColumn("OrderQty", typeof(Int32)),
new DataColumn("LineTotal", typeof(Decimal), "UnitPrice*OrderQty")
};
orderDetailTable.Columns.AddRange(cols);
orderDetailTable.PrimaryKey = new DataColumn[] { orderDetailTable.Columns["OrderDetailId"] };
return orderDetailTable;
}
private static void InsertOrders(DataTable orderTable)
{
// Add one row once.
DataRow row1 = orderTable.NewRow();
row1["OrderId"] = "O0001";
row1["OrderDate"] = new DateTime(2013, 3, 1);
orderTable.Rows.Add(row1);
DataRow row2 = orderTable.NewRow();
row2["OrderId"] = "O0002";
row2["OrderDate"] = new DateTime(2013, 3, 12);
orderTable.Rows.Add(row2);
DataRow row3 = orderTable.NewRow();
row3["OrderId"] = "O0003";
row3["OrderDate"] = new DateTime(2013, 3, 20);
orderTable.Rows.Add(row3);
}
private static void InsertOrderDetails(DataTable orderDetailTable)
{
// Use an Object array to insert all the rows .
// Values in the array are matched sequentially to the columns, based on the order in which they appear in the table.
Object[] rows =
{
new Object[] { 1, "O0001", "Mountain Bike", 1419.5, 36 },
new Object[] { 2, "O0001", "Road Bike", 1233.6, 16 },
new Object[] { 3, "O0001", "Touring Bike", 1653.3, 32 },
new Object[] { 4, "O0002", "Mountain Bike", 1419.5, 24 },
new Object[] { 5, "O0002", "Road Bike", 1233.6, 12 },
new Object[] { 6, "O0003", "Mountain Bike", 1419.5, 48 },
new Object[] { 7, "O0003", "Touring Bike", 1653.3, 8 },
};
foreach (Object[] row in rows)
{
orderDetailTable.Rows.Add(row);
}
}
private static void ShowTable(DataTable table)
{
foreach (DataColumn col in table.Columns)
{
Console.Write("{0,-14}", col.ColumnName);
}
Console.WriteLine();
foreach (DataRow row in table.Rows)
{
foreach (DataColumn col in table.Columns)
{
if (col.DataType.Equals(typeof(DateTime)))
Console.Write("{0,-14:d}", row[col]);
else if (col.DataType.Equals(typeof(Decimal)))
Console.Write("{0,-14:C}", row[col]);
else
Console.Write("{0,-14}", row[col]);
}
Console.WriteLine();
}
Console.WriteLine();
}
}
Imports System.Data
Class Program
Public Shared Sub Main(args As String())
' Create two tables and add them into the DataSet
Dim orderTable As DataTable = CreateOrderTable()
Dim orderDetailTable As DataTable = CreateOrderDetailTable()
Dim salesSet As New DataSet()
salesSet.Tables.Add(orderTable)
salesSet.Tables.Add(orderDetailTable)
' Set the relations between the tables and create the related constraint.
salesSet.Relations.Add("OrderOrderDetail", orderTable.Columns("OrderId"), orderDetailTable.Columns("OrderId"), True)
Console.WriteLine("After creating the foreign key constriant, you will see the following error if inserting order detail with the wrong OrderId: ")
Try
Dim errorRow As DataRow = orderDetailTable.NewRow()
errorRow(0) = 1
errorRow(1) = "O0007"
orderDetailTable.Rows.Add(errorRow)
Catch e As Exception
Console.WriteLine(e.Message)
End Try
Console.WriteLine()
' Insert the rows into the table
InsertOrders(orderTable)
InsertOrderDetails(orderDetailTable)
Console.WriteLine("The initial Order table.")
ShowTable(orderTable)
Console.WriteLine("The OrderDetail table.")
ShowTable(orderDetailTable)
' Use the Aggregate-Sum on the child table column to get the result.
Dim colSub As New DataColumn("SubTotal", GetType([Decimal]), "Sum(Child.LineTotal)")
orderTable.Columns.Add(colSub)
' Compute the tax by referencing the SubTotal expression column.
Dim colTax As New DataColumn("Tax", GetType([Decimal]), "SubTotal*0.1")
orderTable.Columns.Add(colTax)
' If the OrderId is 'Total', compute the due on all orders; or compute the due on this order.
Dim colTotal As New DataColumn("TotalDue", GetType([Decimal]), "IIF(OrderId='Total',Sum(SubTotal)+Sum(Tax),SubTotal+Tax)")
orderTable.Columns.Add(colTotal)
Dim row As DataRow = orderTable.NewRow()
row("OrderId") = "Total"
orderTable.Rows.Add(row)
Console.WriteLine("The Order table with the expression columns.")
ShowTable(orderTable)
Console.WriteLine("Press any key to exit.....")
Console.ReadKey()
End Sub
Private Shared Function CreateOrderTable() As DataTable
Dim orderTable As New DataTable("Order")
' Define one column.
Dim colId As New DataColumn("OrderId", GetType([String]))
orderTable.Columns.Add(colId)
Dim colDate As New DataColumn("OrderDate", GetType(DateTime))
orderTable.Columns.Add(colDate)
' Set the OrderId column as the primary key.
orderTable.PrimaryKey = New DataColumn() {colId}
Return orderTable
End Function
Private Shared Function CreateOrderDetailTable() As DataTable
Dim orderDetailTable As New DataTable("OrderDetail")
' Define all the columns once.
Dim cols As DataColumn() = {New DataColumn("OrderDetailId", GetType(Int32)), New DataColumn("OrderId", GetType([String])), New DataColumn("Product", GetType([String])), New DataColumn("UnitPrice", GetType([Decimal])), New DataColumn("OrderQty", GetType(Int32)), New DataColumn("LineTotal", GetType([Decimal]), "UnitPrice*OrderQty")}
orderDetailTable.Columns.AddRange(cols)
orderDetailTable.PrimaryKey = New DataColumn() {orderDetailTable.Columns("OrderDetailId")}
Return orderDetailTable
End Function
Private Shared Sub InsertOrders(orderTable As DataTable)
' Add one row once.
Dim row1 As DataRow = orderTable.NewRow()
row1("OrderId") = "O0001"
row1("OrderDate") = New DateTime(2013, 3, 1)
orderTable.Rows.Add(row1)
Dim row2 As DataRow = orderTable.NewRow()
row2("OrderId") = "O0002"
row2("OrderDate") = New DateTime(2013, 3, 12)
orderTable.Rows.Add(row2)
Dim row3 As DataRow = orderTable.NewRow()
row3("OrderId") = "O0003"
row3("OrderDate") = New DateTime(2013, 3, 20)
orderTable.Rows.Add(row3)
End Sub
Private Shared Sub InsertOrderDetails(orderDetailTable As DataTable)
' Use an Object array to insert all the rows .
' Values in the array are matched sequentially to the columns, based on the order in which they appear in the table.
Dim rows As [Object]() = {New [Object]() {1, "O0001", "Mountain Bike", 1419.5, 36}, New [Object]() {2, "O0001", "Road Bike", 1233.6, 16}, New [Object]() {3, "O0001", "Touring Bike", 1653.3, 32}, New [Object]() {4, "O0002", "Mountain Bike", 1419.5, 24}, New [Object]() {5, "O0002", "Road Bike", 1233.6, 12}, New [Object]() {6, "O0003", "Mountain Bike", 1419.5, 48}, _
New [Object]() {7, "O0003", "Touring Bike", 1653.3, 8}}
For Each row As [Object]() In rows
orderDetailTable.Rows.Add(row)
Next
End Sub
Private Shared Sub ShowTable(table As DataTable)
For Each col As DataColumn In table.Columns
Console.Write("{0,-14}", col.ColumnName)
Next
Console.WriteLine()
For Each row As DataRow In table.Rows
For Each col As DataColumn In table.Columns
If col.DataType.Equals(GetType(DateTime)) Then
Console.Write("{0,-14:d}", row(col))
ElseIf col.DataType.Equals(GetType([Decimal])) Then
Console.Write("{0,-14:C}", row(col))
Else
Console.Write("{0,-14}", row(col))
End If
Next
Console.WriteLine()
Next
Console.WriteLine()
End Sub
End Class
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