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ConstraintCollection.CollectionChanged Event

Occurs whenever the ConstraintCollection is changed because of Constraint objects being added or removed.

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

public event CollectionChangeEventHandler CollectionChanged

For more information about handling events, see Consuming Events.

The following example demonstrates how to use the CollectionChanged event.

    private static void ConstraintCollectionChanged()
        // Demonstrate ConstraintCollection.CollectionChanged event. 
            // Create Customers table.
            DataTable customersTable = new DataTable("Customers");
            customersTable.Columns.Add("id", typeof(int));
            customersTable.Columns.Add("Name", typeof(string));
            customersTable.Constraints.CollectionChanged += 
                new System.ComponentModel.CollectionChangeEventHandler( 

            // Create Orders table.
            DataTable ordersTable = new DataTable("Orders");
            ordersTable.Columns.Add("CustID", typeof(int));
            ordersTable.Columns.Add("CustName", typeof(string));
            ordersTable.Constraints.CollectionChanged += 
                new System.ComponentModel.CollectionChangeEventHandler(

            // Create unique constraint.
            UniqueConstraint constraint = new UniqueConstraint(
            // Create unique constraint and specify as primary key.
                "pKey", ordersTable.Columns["CustID"], true);

            // Remove constraints.

            // Results in an Exception. You can't remove  
            // a primary key constraint.
        catch(Exception ex)
            // Process exception and return.
            Console.WriteLine("Exception of type {0} occurred.", 

    private static void Collection_Changed(object sender, 
        System.ComponentModel.CollectionChangeEventArgs ex)
        Console.WriteLine("List_Changed Event: '{0}'\t element={1}", 
            ex.Action, ex.Element);

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

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

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 3.5, 2.0, 1.0

XNA Framework

Supported in: 3.0, 2.0, 1.0