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ConstraintCollection.CanRemove Method

Indicates whether a Constraint can be removed.

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

public bool CanRemove(
	Constraint constraint
)

Parameters

constraint
Type: System.Data.Constraint

The Constraint to be tested for removal from the collection.

Return Value

Type: System.Boolean
true if the Constraint can be removed from collection; otherwise, false.

The default behavior whenever a DataRelation is added to a DataSet, is to add a ForeignKeyConstraint to the parent table and a UniqueConstraint to the child table. The UniqueConstraint is applied to the primary key column of the parent table, and the ForeignKeyConstraint is applied to the foreign key column of the child table. Because trying to remove the UniqueConstraint before removing the ForeignKeyConstraint causes an exception to be thrown, you should always use the CanRemove method before calling Remove, to make sure that the UniqueConstraint can be removed.

The following example uses the CanRemove method to determine whether a Constraint can be removed, before trying to remove it.

private void TryRemove(DataSet dataSet)
{
    try
    {
        DataTable customersTable = dataSet.Tables["Customers"];
        Constraint constraint = customersTable.Constraints[0];
        Console.WriteLine("Can remove? " + 
            customersTable.Constraints.CanRemove(constraint));
    }
    catch(Exception ex) 
    {
        // Process exception and return.
        Console.WriteLine("Exception of type {0} occurred.", 
            ex.GetType());
    }
}

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
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