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DataTable.ColumnChanging Event

Occurs when a value is being changed for the specified DataColumn in a DataRow.

[Visual Basic]
Public Event ColumnChanging As DataColumnChangeEventHandler
[C#]
public event DataColumnChangeEventHandler ColumnChanging;
[C++]
public: __event DataColumnChangeEventHandler* ColumnChanging;

[JScript] In JScript, you can handle the events defined by a class, but you cannot define your own.

Event Data

The event handler receives an argument of type DataColumnChangeEventArgs containing data related to this event. The following DataColumnChangeEventArgs properties provide information specific to this event.

Property Description
Column Gets the DataColumn with a changing value.
ProposedValue Gets or sets the proposed new value for the column.
Row Gets the DataRow of the column with a changing value.

Remarks

For more information see Working with DataTable Events.

Example

[Visual Basic] 
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

[C#] 
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 );
}

[C++] 

public:
    static void DataTableColumnChanging() {
    DataTable* custTable = new DataTable(S"Customers");
    // add columns
    custTable->Columns->Add(S"id", __typeof(int));
    custTable->Columns->Add(S"name", __typeof(String));
    custTable->Columns->Add(S"address", __typeof(String));

    // set PrimaryKey
    custTable->Columns->Item[ S"id" ]->Unique = true;
    DataColumn* ColumnArray[] = { custTable->Columns->Item[S"id"] };
    custTable->PrimaryKey = ColumnArray;

    // add a ColumnChanging event handler for the table.
    custTable->ColumnChanging += new DataColumnChangeEventHandler(0, Column_Changing);

    // add ten rows
    for (int id=1; id<=10; id++) {
        Object* temp0 [] = {__box(id), String::Format(S"customer {0}", __box(id)), String::Format(S"address {0}", __box(id)) };
        custTable->Rows->Add(temp0);
    }

    custTable->AcceptChanges();

    // change the name column in all the rows
    System::Collections::IEnumerator* myEnum = custTable->Rows->GetEnumerator();
    while (myEnum->MoveNext()) {
        DataRow* row = __try_cast<DataRow*>(myEnum->Current);
        row->Item[S"name"] = String::Format(S"vip {0}", row->Item[S"id"]);
    }

}

public:
    static void Column_Changing(Object* sender, System::Data::DataColumnChangeEventArgs* e) {
        Console::WriteLine(S"Column_Changing Event: name= {0}; Column= {1}; proposed name= {2}",
        e->Row->Item[S"name"], e->Column->ColumnName, e->ProposedValue);
    }

[JScript] No example is available for JScript. To view a Visual Basic, C#, or C++ example, click the Language Filter button Language Filter in the upper-left corner of the page.

Requirements

Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family

See Also

DataTable Class | DataTable Members | System.Data Namespace

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