DataTableCollection.CollectionChanged-Ereignis

Tritt ein, wenn die DataTableCollection aufgrund des Hinzufügens oder Entfernens von DataTable-Objekten geändert wurde.

Namespace: System.Data
Assembly: System.Data (in system.data.dll)

Syntax

'Declaration
Public Event CollectionChanged As CollectionChangeEventHandler
'Usage
Dim instance As DataTableCollection
Dim handler As CollectionChangeEventHandler

AddHandler instance.CollectionChanged, handler

public event CollectionChangeEventHandler CollectionChanged

public:
event CollectionChangeEventHandler^ CollectionChanged {
    void add (CollectionChangeEventHandler^ value);
    void remove (CollectionChangeEventHandler^ value);
}

/** @event */
public void add_CollectionChanged (CollectionChangeEventHandler value)

/** @event */
public void remove_CollectionChanged (CollectionChangeEventHandler value)

JScript unterstützt die Verwendung von Ereignissen, aber nicht die Deklaration von neuen Ereignissen.

Hinweise

Weitere Informationen über die Behandlung von Ereignissen finden Sie unter Behandeln von Ereignissen.

Beispiel

Im folgenden Beispiel wird die Verwendung des CollectionChanged-Ereignisses veranschaulicht.

Public Sub TableCollectionCollectionChanged()
    ' create a DataSet with two tables
    Dim dataSet As DataSet = New DataSet()

    AddHandler dataSet.Tables.CollectionChanging, _
        AddressOf Collection_Changed

    ' create Customer table
    Dim custTable As DataTable = New DataTable("Customers")
    custTable.Columns.Add("customerId", _
        System.Type.GetType("System.Integer")).AutoIncrement = True
    custTable.Columns.Add("name", System.Type.GetType("System.String"))
    custTable.PrimaryKey = New DataColumn() {custTable.Columns("customerId")}

    ' create Orders table
    Dim orderTable As DataTable = New DataTable("Orders")
    orderTable.Columns.Add("orderId", _
        System.Type.GetType("System.Integer")).AutoIncrement = True
    orderTable.Columns.Add("customerId", System.Type.GetType("System.Integer"))
    orderTable.Columns.Add("amount", System.Type.GetType("System.Double"))
    orderTable.PrimaryKey = New DataColumn() {orderTable.Columns("orderId")}

    dataSet.Tables.AddRange(New DataTable() {custTable, orderTable})

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

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

Private Sub Collection_Changed(ByVal sender As Object, _
    ByVal e As System.ComponentModel.CollectionChangeEventArgs)
    Console.WriteLine("Collection_Changed Event: '{0}'\table element={1}", _
        e.Action.ToString(), e.Element.ToString())
End Sub

public static void TableCollectionCollectionChanged()
{
    // create a DataSet with two tables
    DataSet dataSet = new DataSet();

    dataSet.Tables.CollectionChanged +=
        new System.ComponentModel.CollectionChangeEventHandler(
        Collection_Changed);

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

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

    dataSet.Tables.AddRange(new DataTable[] { custTable, orderTable });

    // remove all tables
    // check if table can be removed and then
    // remove it, cannot use a foreach when
    // removing items from a collection
    // equivalent to dataSet.Tables.Clear()
    while (dataSet.Tables.Count > 0)
    {
        DataTable table = dataSet.Tables[0];
        if (dataSet.Tables.CanRemove(table))
        {
            dataSet.Tables.RemoveAt(0);
        }
    }

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

private static void Collection_Changed(object sender,
    System.ComponentModel.CollectionChangeEventArgs e)
{
    Console.WriteLine("Collection_Changed Event: '{0}'\table element={1}",
        e.Action.ToString(), e.Element.ToString());
}

Plattformen

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

.NET Framework unterstützt nicht alle Versionen sämtlicher Plattformen. Eine Liste der unterstützten Versionen finden Sie unter Systemanforderungen.

Versionsinformationen

.NET Framework

Unterstützt in: 2.0, 1.1, 1.0

.NET Compact Framework

Unterstützt in: 2.0, 1.0

Siehe auch

Referenz

DataTableCollection-Klasse
DataTableCollection-Member
System.Data-Namespace