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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(

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

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