DataTable.ColumnChanging 事件

在 DataRow 中指定的 DataColumn 的值发生更改时发生。

**命名空间:**System.Data
**程序集:**System.Data（在 system.data.dll 中）

语法

声明
Public Event ColumnChanging As DataColumnChangeEventHandler
用法
Dim instance As DataTable
Dim handler As DataColumnChangeEventHandler

AddHandler instance.ColumnChanging, handler

public event DataColumnChangeEventHandler ColumnChanging

public:
event DataColumnChangeEventHandler^ ColumnChanging {
    void add (DataColumnChangeEventHandler^ value);
    void remove (DataColumnChangeEventHandler^ value);
}

/** @event */
public void add_ColumnChanging (DataColumnChangeEventHandler value)

/** @event */
public void remove_ColumnChanging (DataColumnChangeEventHandler value)

JScript 支持使用事件，但不支持进行新的声明。

备注

有关更多信息，请参见 使用 DataTable 事件。

示例

Private Shared Sub DataTableColumnChanging()
    Dim custTable As DataTable = New DataTable("Customers")
    ' add columns
    custTable.Columns.Add("id", Type.GetType("System.Int32"))
    custTable.Columns.Add("name", Type.GetType("System.String"))
    custTable.Columns.Add("address", Type.GetType("System.String"))

    ' set PrimaryKey
    custTable.Columns("id").Unique = true
    custTable.PrimaryKey = New DataColumn() { custTable.Columns("id") }

    ' add a ColumnChanging event handler for the table.
    AddHandler custTable.ColumnChanging, New _
        DataColumnChangeEventHandler(AddressOf Column_Changing )

    ' add ten rows
    Dim id As Integer
    For id = 1 To 10
        custTable.Rows.Add( _
            New Object() { id, string.Format("customer{0}", id), _
                string.Format("address{0}", id) })
    Next
    
    custTable.AcceptChanges()

    ' change the name column in all the rows
    Dim row As DataRow
    For Each row In custTable.Rows 
        row("name") = string.Format("vip{0}", row("id"))
    Next

End Sub

Private Shared Sub Column_Changing(sender As Object, _
    e As DataColumnChangeEventArgs)
    Console.WriteLine( _
        "Column_Changing Event: name={0}; Column={1}; proposed name={2}", _
        e.Row("name"), e.Column.ColumnName, e.ProposedValue) 
End Sub

private static void DataTableColumnChanging()
{
    DataTable custTable = new DataTable("Customers");
    // add columns
    custTable.Columns.Add("id", typeof(int));
    custTable.Columns.Add("name", typeof(string));
    custTable.Columns.Add("address", typeof(string));

    // set PrimaryKey
    custTable.Columns[ "id" ].Unique = true;
    custTable.PrimaryKey = new DataColumn[] { custTable.Columns["id"] };

    // add a ColumnChanging event handler for the table.
    custTable.ColumnChanging += new 
        DataColumnChangeEventHandler(Column_Changing );


    // add ten rows
    for(int id=1; id<=10; id++)
    {
        custTable.Rows.Add(
            new object[] { id, string.Format(
            "customer{0}", id), string.Format("address{0}", id) });
    }

    custTable.AcceptChanges();

    // change the name column in all the rows
    foreach(DataRow row in custTable.Rows )
    {
        row["name"] = string.Format("vip{0}", row["id"]);
    }

}

private static void Column_Changing(object sender, 
    DataColumnChangeEventArgs e )
{
    Console.WriteLine(
        "Column_Changing Event: name={0}; Column={1}; proposed name={2}", 
        e.Row["name"], e.Column.ColumnName, e.ProposedValue );
}

平台

Windows 98、Windows 2000 SP4、Windows CE、Windows Millennium Edition、Windows Mobile for Pocket PC、Windows Mobile for Smartphone、Windows Server 2003、Windows XP Media Center Edition、Windows XP Professional x64 Edition、Windows XP SP2、Windows XP Starter Edition

.NET Framework 并不是对每个平台的所有版本都提供支持。有关受支持版本的列表，请参见系统要求。

版本信息

.NET Framework

受以下版本支持：2.0、1.1、1.0

.NET Compact Framework

受以下版本支持：2.0、1.0

请参见

参考

DataTable 类
DataTable 成员
System.Data 命名空间

其他资源

创建和使用 DataTables