UniqueConstraint Class
Represents a restriction on a set of columns in which all values must be unique.
For a list of all members of this type, see UniqueConstraint Members.
System.Object
System.Data.Constraint
System.Data.UniqueConstraint
[Visual Basic] <Serializable> Public Class UniqueConstraint Inherits Constraint [C#] [Serializable] public class UniqueConstraint : Constraint [C++] [Serializable] public __gc class UniqueConstraint : public Constraint [JScript] public Serializable class UniqueConstraint extends Constraint
Thread Safety
This type is suitable for multithreaded read operations. You must synchronize any write operations.
Remarks
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.
Example
[Visual Basic] The following example adds a UniqueConstraint to a DataSet and sets the EnforceConstraints property to true.
[Visual Basic]
Public Sub CreateTable()
Dim myTable As DataTable = New DataTable
myTable.Columns.Add("CustomerID", Type.GetType("System.String"))
myTable.Columns.Add("CompanyName", Type.GetType("System.String"))
Dim myUC As UniqueConstraint = New UniqueConstraint("CustConstraint", _
New DataColumn() {myTable.Columns("CustomerID"), _
myTable.Columns("CompanyName")} )
myTable.Constraints.Add(myUC)
End Sub
[C#, C++, JScript] No example is available for C#, C++, or JScript. To view a Visual Basic example, click the Language Filter button
in the upper-left corner of the page.
Requirements
Namespace: System.Data
Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family, .NET Compact Framework
Assembly: System.Data (in System.Data.dll)
See Also
UniqueConstraint Members | System.Data Namespace | Add | Constraint | Constraints | ConstraintCollection | DataRelation | ForeignKeyConstraint