Represents a restriction on a set of columns in which all values must be unique.
Object
Constraint
UniqueConstraint
[Visual Basic] Public Class UniqueConstraint Inherits Constraint [C#] public class UniqueConstraint : Constraint [C++] public __gc class UniqueConstraint : public Constraint [JScript] public class UniqueConstraint extends Constraint
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.
Namespace: System.Data
Assembly: System.Data.dll
The following example adds a UniqueConstraint to a DataSet and sets the EnforceConstraints property to true.
[Visual Basic]
' The next line goes into the Declarations section of the module: ' SuppliersProducts is a class derived from DataSet. Private myDataSet As SuppliersProducts Private Sub CreateUniqueConstraint() Dim myUC As UniqueConstraint myUC = New UniqueConstraint _ (myDataSet.Tables("Suppliers"), _ myDataSet.Tables("Suppliers").Columns("CompanyID")) End Sub
UniqueConstraint Members | System.Data Namespace | Constraint | ForeignKeyConstraint | DataRelation | AddKeyConstraint | Constraints