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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 System.Data.dll)

'Declaration
Public Property Unique As Boolean
'Usage
Dim instance As DataColumn 
Dim value As Boolean 

value = instance.Unique

instance.Unique = value

Property Value

Type: System.Boolean
true if the value must be unique; otherwise, false. The default is false.

ExceptionCondition
ArgumentException

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 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

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