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ConstraintCollection.Add Method (Constraint)

Adds the specified Constraint object to the collection.

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

public void Add(
	Constraint constraint


Type: System.Data.Constraint

The Constraint to add.


The constraint argument is null.


The constraint already belongs to this collection, or belongs to another collection.


The collection already has a constraint with the same name. (The comparison is not case-sensitive.)

If the collection is successfully changed by adding or removing constraints, the CollectionChanged event occurs.

The following example adds a UniqueConstraint to the ConstraintCollection of a DataTable.

private void AddConstraint(DataTable table)
    UniqueConstraint uniqueConstraint;
    // Assuming a column named "UniqueColumn" exists, and 
    // its Unique property is true.
    uniqueConstraint = new UniqueConstraint(

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