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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 CollectionChangeEventHandler CollectionChanging
/** @event */
public void add_CollectionChanging (CollectionChangeEventHandler value)

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

JScript supports the use of events, but not the declaration of new ones.

For more information about handling events, see Consuming Events.

The following example demonstrates how to use the CollectionChanging event.

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

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

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

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

    dataSet.Tables.AddRange(new DataTable[] { customersTable, ordersTable );

    // Check to see if each table can be removed and then
    // remove it.
    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_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'\table element={1",
        e.Action.ToString(), e.Element.ToString());


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

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.

.NET Framework

Supported in: 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0

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