DataColumn.Unique Property

Gets or sets a value that indicates whether the values in each row of the column must be unique.

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

Public Property Unique As Boolean
Dim instance As DataColumn
Dim value As Boolean

value = instance.Unique

instance.Unique = value
/** @property */
public boolean get_Unique ()

/** @property */
public void set_Unique (boolean value)

public function get Unique () : boolean

public function set Unique (value : boolean)

Not applicable.

Property Value

true if the value must be unique; otherwise, false. The default is false.

Exception typeCondition


The column is a calculated column.

As soon as this property is changed from false to true, a unique constraint will be created on this column to make sure that values are unique.

The following example creates new DataColumn, sets its properties, and adds it to a table's columns collection.

Private Sub AddColumn(table As DataTable)
    ' Add a DataColumn to the collection and set its properties.
    ' The constructor sets the ColumnName of the column.
    Dim column As DataColumn = New DataColumn("Total")
    column.DataType = System.Type.GetType("System.Decimal")
    column.ReadOnly = True
    column.Expression = "UnitPrice * Quantity"
    column.Unique = False
End Sub

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