Gets the collection of constraints maintained by this table.
(in System.Data.dll)
Visual Basic (Declaration)
Public ReadOnly Property Constraints As ConstraintCollection
Dim instance As DataTable
Dim value As ConstraintCollection
value = instance.Constraints
public ConstraintCollection Constraints { get; }
public:
property ConstraintCollection^ Constraints {
ConstraintCollection^ get ();
}
public function get Constraints () : ConstraintCollection
A ForeignKeyConstraint restricts the action performed when a value in a column (or columns) is either deleted or updated. Such a constraint is intended to be used with primary key columns. In a parent/child relationship between two tables, deleting a value from the parent table can affect the child rows in one of the following ways.
The child rows can also be deleted (a cascading action).
The values in the child column (or columns) can be set to null values.
The values in the child column (or columns) can be set to default values.
An exception can be generated.
A UniqueConstraint becomes active when attempting to set a value in a primary key to a non-unique value.
The following example adds a ForeignKeyConstraint to the collection of constraints.
Private Sub CreateConstraint(dataSet As DataSet, _
table1 As String, table2 As String, _
column1 As String, column2 As String)
Dim idKeyRestraint As ForeignKeyConstraint = _
New ForeignKeyConstraint _
(dataSet.Tables(table1).Columns(column1), _
dataSet.Tables(table2).Columns(column2))
' Set null values when a value is deleted.
idKeyRestraint.DeleteRule = Rule.SetNull
idKeyRestraint.UpdateRule = Rule.Cascade
' Set AcceptRejectRule to cascade changes.
idKeyRestraint.AcceptRejectRule = AcceptRejectRule.Cascade
dataSet.Tables(table1).Constraints.Add(idKeyRestraint)
dataSet.EnforceConstraints = True
End Sub
private void CreateConstraint(DataSet dataSet,
string table1, string table2, string column1, string column2)
{
ForeignKeyConstraint idKeyRestraint = new
ForeignKeyConstraint(dataSet.Tables[table1].Columns[column1],
dataSet.Tables[table2].Columns[column2]);
// Set null values when a value is deleted.
idKeyRestraint.DeleteRule = Rule.SetNull;
idKeyRestraint.UpdateRule = Rule.Cascade;
// Set AcceptRejectRule to cascade changes.
idKeyRestraint.AcceptRejectRule = AcceptRejectRule.Cascade;
dataSet.Tables[table1].Constraints.Add(idKeyRestraint);
dataSet.EnforceConstraints = true;
}
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
Reference
Other Resources