NGWS SDK Documentation  

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ForeignKeyConstraint.DeleteRule

Gets or sets the action that occurs across this constraint on when a row is deleted.

[Visual Basic]
Overridable Public Property DeleteRule As Rule
[C#]
public Rule DeleteRule {virtual get; virtual set;}
[C++]
public: __property virtual Rule get_DeleteRule();
public: __property virtual void set_DeleteRule(Rule);
[JScript]
public function get DeleteRule() : Rule;
public function set DeleteRule(Rule);

Property Value

One of the Rule values. The default is Cascade. Possible values include: None, Cascade, SetNull, SetDefault, and Default.

Remarks

When a row is deleted from a parent table, the DeleteRule determines what will happen in the columns of the child table (or tables). If the rule is set to Cascade, child rows will be deleted.

If set to SetNull, a DBnull will be placed in the appropriate columns of the affected rows. Depending on your DBMS, a null value may or may not be permitted in a column. For example, SQLServer allows multiple null values to be found in a primary key column, even if they are not unique. In a DataTable, however, if a DataColumn object's Unique property is set to true, multiple null values are not allowed in primary key columns.

If set to Default, the default value for the column is assigned.

Example [Visual Basic]

The following example creates a ForeignKeyConstraint, sets various of its properties, and adds it to a DataTable object's ConstraintsCollection.

[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 CreateConstraint()
   ' Declare parent column and child column variables.
   Dim pCol As DataColumn
   Dim cCol As DataColumn
   Dim myFKC As ForeignKeyConstraint
   ' Set parent and child column variables.
   pCol = MyDataSet.Tables("Suppliers).Columns("SupplierID")
   cCol = MyDataSet.Tables("Products").Columns("SupplieriD")
   myFKC = New ForeignKeyConstraint("SuppierFKConstraint", pCol, cCol)
   ' Set null values when a value is deleted.
   myFKC.DeleteRule = Rule.SetNull
   myFKC.UpdateRule = Rule.Cascade
   myFKC.AcceptRejectRule = AcceptRejectRule.Cascade
   ' Add the constraint, and set EnforceConstraints to true.
   myDataSet.Tables("Suppliers").Constraints.Add myFKC
   myDataSet.EnforceConstraints = True
End Sub

See Also

ForeignKeyConstraint Class | ForeignKeyConstraint Members | System.Data Namespace