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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 System.Data.dll)

public Constraint Add(
	string name,
	DataColumn[] columns,
	bool primaryKey


Type: System.String
The name of the UniqueConstraint.
Type: System.Data.DataColumn[]
An array of DataColumn objects to which the constraint applies.
Type: System.Boolean
Specifies whether the column should be the primary key. If true, the column will be a primary key column.

Return Value

Type: System.Data.Constraint
A new UniqueConstraint.


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);

.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.