CollectionChanging Event
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DataTableCollection.CollectionChanging Event


Occurs while the DataTableCollection is changing because of DataTable objects being added or removed.

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

Public Event CollectionChanging As CollectionChangeEventHandler

For more information about handling events, see NIB: Consuming Events.

The following example demonstrates how to use the CollectionChanging event.

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

    AddHandler dataSet.Tables.CollectionChanging, _
        AddressOf Collection_Changing

    ' Create Customer table
    Dim customersTable As DataTable = New DataTable("Customers")
    customersTable.Columns.Add("customerId", _
        System.Type.GetType("System.Integer")).AutoIncrement = True
    customersTable.Columns.Add("name", _
    customersTable.PrimaryKey = New DataColumn() _

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

    ' Add the tables to the DataTableCollection
    dataSet.Tables.AddRange(New DataTable() {customersTable, ordersTable})

    ' 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 (dataSet.Tables.Count > 0)
        Dim table As DataTable
        table = dataSet.Tables(0)
        If (dataSet.Tables.CanRemove(table)) Then
        End If

    Console.WriteLine("dataSet has {0} tables", dataSet.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}'\table element={1}", _
        e.Action.ToString(), e.Element.ToString())
End Sub

.NET Framework
Available since 1.1
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