DataTableCollection.CollectionChanging イベント

DataTable オブジェクトを追加または削除した結果として DataTableCollection が変更されているときに発生します。

Public Event CollectionChanging As CollectionChangeEventHandler
[C#]
public event CollectionChangeEventHandler CollectionChanging;
[C++]
public: __event CollectionChangeEventHandler* CollectionChanging;

[JScript] JScript では、このクラスで定義されているイベントを処理できます。ただし、独自に定義することはできません。

イベント データ

イベント ハンドラが、このイベントに関連するデータを含む、CollectionChangeEventArgs 型の引数を受け取りました。次の CollectionChangeEventArgs プロパティには、このイベントの固有の情報が記載されます。

解説

イベント処理の詳細については、「 イベントの利用 」を参照してください。

使用例

[Visual Basic, C#, C++] CollectionChanging イベントを使用する方法の例を次に示します。

 
Public Sub TableCollectionCollectionChanging()
    ' Create a DataSet with two tables
    Dim myDataSet As DataSet = New DataSet()

    AddHandler myDataSet.Tables.CollectionChanging, AddressOf Collection_Changing

    ' Create Customer table
    Dim t As DataTable = New DataTable("Customers")
    t.Columns.Add("customerId", System.Type.GetType("System.Integer")).AutoIncrement = True
    t.Columns.Add("name", System.Type.GetType("System.String"))
    t.PrimaryKey = New DataColumn() {t.Columns("customerId")}

    ' Create Orders table
    Dim t2 As DataTable = New DataTable("Orders")
    t2.Columns.Add("orderId", System.Type.GetType("System.Integer")).AutoIncrement = True
    t2.Columns.Add("customerId", System.Type.GetType("System.Integer"))
    t2.Columns.Add("amount", System.Type.GetType("System.Double"))
    t2.PrimaryKey = New DataColumn() {t.Columns("orderId")}

    ' Add the tables to the DataTableCollection
    myDataSet.Tables.AddRange(New DataTable() {t, t2})

    ' Remove all tables
    ' First check to see if the table can be removed and
    ' then remove it.
    '
    ' You cannot use a For Each loop to remove items
    ' from a collection.
    Do While (myDataSet.Tables.Count > 0)
        Dim table As DataTable
        table = myDataSet.Tables(0)
        If (myDataSet.Tables.CanRemove(table)) Then
            myDataSet.Tables.RemoveAt(0)
        End If
    Loop

    Console.WriteLine("myDataSet has {0} tables", myDataSet.Tables.Count)
End Sub

Private Sub Collection_Changing(ByVal sender As Object, ByVal e As System.ComponentModel.CollectionChangeEventArgs)
    ' Implementing this event allows you to abort a change
    ' to the collection by raising an exception which you can
    ' catch.
    Console.WriteLine("Collection_Changing Event: '{0}'\t element={1}", _
        e.Action.ToString(), e.Element.ToString())
End Sub

[C#] 
public static void TableCollectionCollectionChanging()
{
    // Create a DataSet with two tables
    DataSet myDataSet = new DataSet();

    // Assign the event-handler function for the CollectionChangeEvent.
    myDataSet.Tables.CollectionChanging += 
        new System.ComponentModel.CollectionChangeEventHandler( Collection_Changing );

    // create Customer table
    DataTable t = new DataTable( "Customers" );
    t.Columns.Add( "customerId", typeof(int)    ).AutoIncrement = true;
    t.Columns.Add( "name",       typeof(string) );
    t.PrimaryKey = new DataColumn[] { t.Columns["customerId"] };

    // create Orders table
    DataTable t2 = new DataTable( "Orders" );
    t2.Columns.Add( "orderId",    typeof(int)    ).AutoIncrement = true;
    t2.Columns.Add( "customerId", typeof(int)    );
    t2.Columns.Add( "amount",     typeof(double) );
    t2.PrimaryKey = new DataColumn[] { t.Columns["orderId"] };

    myDataSet.Tables.AddRange( new DataTable[] {t, t2} );

    // Check to see if each table can be removed and then
    // remove it.
    while( myDataSet.Tables.Count > 0 )
    {
        DataTable table = myDataSet.Tables[0];
        if( myDataSet.Tables.CanRemove( table ) )
        {
            myDataSet.Tables.RemoveAt( 0 );
        }
    }

    Console.WriteLine( "myDataSet has {0} tables", myDataSet.Tables.Count );
}

private static void Collection_Changing(object sender, System.ComponentModel.CollectionChangeEventArgs e)
{
    // Implementing this event allows you to abort a change
        // to the collection by raising an exception which you can
        // catch.

    Console.WriteLine( "Collection_Changing Event: '{0}'\t element={1}", 
        e.Action.ToString(), e.Element.ToString() );
}

[C++] 
public:
   static void TableCollectionCollectionChanging()
   {
      // Create a DataSet with two tables
      DataSet* myDataSet = new DataSet();

      // Assign the event-handler function for the CollectionChangeEvent.
      myDataSet->Tables->CollectionChanging += 
         new System::ComponentModel::CollectionChangeEventHandler(0,  Collection_Changing );

      // create Customer table
      DataTable* t = new DataTable( S"Customers" );
      t->Columns->Add( S"customerId", __typeof(int)    )->AutoIncrement = true;
      t->Columns->Add( S"name",       __typeof(String) );

      DataColumn* temp1 [] = {t->Columns->Item[S"customerId"]};
      t->PrimaryKey = temp1;

      // create Orders table
      DataTable* t2 = new DataTable( S"Orders" );
      t2->Columns->Add( S"orderId",    __typeof(int)    )->AutoIncrement = true;
      t2->Columns->Add( S"customerId", __typeof(int)    );
      t2->Columns->Add( S"amount",     __typeof(double) );

      DataColumn* temp2 [] = {t->Columns->Item[S"orderId"]};
      t2->PrimaryKey = temp2;

      DataTable* temp0 [] = {t, t2};
      myDataSet->Tables->AddRange( temp0 );

      // Check to see if each table can be removed and then
      // remove it.
      while( myDataSet->Tables->Count > 0 )
      {
         DataTable* table = myDataSet->Tables->Item[0];
         if( myDataSet->Tables->CanRemove( table ) )
         {
            myDataSet->Tables->RemoveAt( 0 );
         }
      }

      Console::WriteLine( S"myDataSet has {0} tables", __box(myDataSet->Tables->Count));
   }

private:
   static void Collection_Changing(Object* /*sender*/, System::ComponentModel::CollectionChangeEventArgs* e)
   {
      // Implementing this event allows you to abort a change
      // to the collection by raising an exception which you can
      // catch.

      Console::WriteLine( S"Collection_Changing Event: '{0}'\t element={1}",
         __box(e->Action), e->Element );
   }

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必要条件

プラットフォーム: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 ファミリ

参照

DataTableCollection クラス | DataTableCollection メンバ | System.Data 名前空間