System.Data.DataTable 类
本文提供了此 API 参考文档的补充说明。
该 DataTable 类是 ADO.NET 库中的中心对象。 使用 DataTable 的其他对象包括 DataSet 和 DataView.
DataTable 对象名称在条件上区分大小写。 例如，如果一个 DataTable 名为“mydatatable”，另一个名为“Mydatatable”，则用于搜索其中一个表的字符串被视为区分大小写。 但是，如果“mydatatable”存在且“Mydatatable”不存在，则搜索字符串被视为不区分大小写。 A DataSet 可以包含两 DataTable 个具有相同 TableName 属性值但不同 Namespace 属性值的对象。 有关使用 DataTable 对象的详细信息，请参阅 创建 DataTable。
如果要以编程方式创建， DataTable 必须先通过将对象添加到 DataColumnDataColumnCollection （通过 Columns 属性访问）来定义其架构。 有关添加 DataColumn 对象的详细信息，请参阅 向 DataTable 添加列。
若要向 a DataTable添加行，必须先使用 NewRow 该方法返回新 DataRow 对象。 该方法 NewRow 返回一行，其架构 DataTable为表 DataColumnCollection的定义。 可存储的最大行 DataTable 数为 16,777,216。 有关详细信息，请参阅 将数据添加到 DataTable。
它还 DataTable 包含可用于确保数据完整性的对象集合 Constraint 。 有关详细信息，请参阅DataTable 约束。
有许多 DataTable 事件可用于确定何时对表进行更改。 其中包括 RowChanged、RowChanging、RowDeleting 和 RowDeleted。 有关可用于 a DataTable的事件的详细信息，请参阅 处理 DataTable 事件。
创建实例 DataTable 时，某些读/写属性将设置为初始值。 有关这些值的列表，请参阅 DataTable 构造函数。
注意
DataTable和DataSet对象继承自MarshalByValueComponent并支持 ISerializable .NET 远程处理接口。 这些是可用于 .NET 远程处理的唯一 ADO.NET 对象。
安全注意事项
有关 DataSet 和 DataTable 安全性的信息，请参阅 安全指南。
示例
此示例演示如何使用特定的架构定义手动创建 DataTable：
- 创建多个 DataTable 并定义初始列。
- 创建表约束。
- 插入值并显示表。
- 创建表达式列并显示表。
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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