ConstraintCollection.Add Method (String, DataColumn[], Boolean)

Constructs a new UniqueConstraint with the specified name, array of DataColumn objects, and value that indicates whether the column is a primary key, and adds it to the collection.

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

public Constraint Add (
	string name,
	DataColumn[] columns,
	bool primaryKey
public Constraint Add (
	String name, 
	DataColumn[] columns, 
	boolean primaryKey
public function Add (
	name : String, 
	columns : DataColumn[], 
	primaryKey : boolean
) : Constraint
Not applicable.



The name of the UniqueConstraint.


An array of DataColumn objects to which the constraint applies.


Specifies whether the column should be the primary key. If true, the column will be a primary key column.

Return Value

A new UniqueConstraint.

Exception typeCondition


The constraint already belongs to this collection.


The constraint belongs to another collection.


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

The CollectionChanged event occurs if the constraint is added successfully.

The following example creates an array of DataColumn objects that are used to create a new UniqueConstraint in a specific DataTable.

private void AddUniqueConstraint(DataTable table)
    DataColumn[] columns = new DataColumn[1];
    columns[0] = table.Columns["ID"];
    columns[1] = table.Columns["Name"];
    table.Constraints.Add("idNameConstraint", columns, true);

Windows 98, Windows Server 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 Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0

XNA Framework

Supported in: 1.0