UniqueConstraint Class
Assembly: System.Data (in system.data.dll)
The UniqueConstraint is enforced on a single column (or columns) to ensure that a primary key value is unique.
Constraints are not enforced unless the EnforceConstraints property is set to true.
When the a DataSet is merged with a second DataSet, constraints are not enforced until all merges are completed.
The following example adds a UniqueConstraint to a DataSet and sets the EnforceConstraints property to true.
Public Sub CreateDataTable() Dim dataTable As DataTable = New DataTable dataTable.Columns.Add("CustomerID", Type.GetType("System.String")) dataTable.Columns.Add("CompanyName", Type.GetType("System.String")) Dim uniqueConstraint As UniqueConstraint = _ New UniqueConstraint("CustConstraint", _ New DataColumn() {dataTable.Columns("CustomerID"), _ dataTable.Columns("CompanyName")) dataTable.Constraints.Add(uniqueConstraint) End Sub
Windows 98, Windows 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 .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.