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DataColumn.Unique Property

Definition

Namespace:
System.Data
Assemblies:
netstandard.dll, System.Data.Common.dll
Assembly:
System.Data.Common.dll
Assembly:
System.Data.dll
Assembly:
netstandard.dll
Source:
DataColumn.cs
Source:
DataColumn.cs
Source:
DataColumn.cs
Source:
DataColumn.cs
Source:
DataColumn.cs

Important

Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.

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

public:
 property bool Unique { bool get(); void set(bool value); };
public bool Unique { get; set; }
[System.Data.DataSysDescription("DataColumnUniqueDescr")]
public bool Unique { get; set; }
member this.Unique : bool with get, set
[<System.Data.DataSysDescription("DataColumnUniqueDescr")>]
member this.Unique : bool with get, set
Public Property Unique As Boolean

Property Value

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

Attributes

Exceptions

The column is a calculated column.

Examples

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

private void AddColumn(DataTable table)
{
 // Add a DataColumn to the collection and set its properties.
 // The constructor sets the ColumnName of the column.
 DataColumn column = new DataColumn("Total");
 column.DataType = System.Type.GetType("System.Decimal");
 column.ReadOnly = true;
 column.Expression = "UnitPrice * Quantity";
 column.Unique = false;
}

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 New DataColumn("Total")
 column.DataType = System.Type.GetType("System.Decimal")
 column.ReadOnly = True
 column.Expression = "UnitPrice * Quantity"
 column.Unique = False
End Sub

Remarks

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.

Applies to

See also

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