DeleteRule Property

ForeignKeyConstraint.DeleteRule Property


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

Namespace:   System.Data
Assembly:  System.Data (in System.Data.dll)

public virtual Rule DeleteRule { get; set; }

Property Value

Type: System.Data.Rule

One of the Rule values. The default is Cascade.

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 data source, 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 SetDefault, the default value for the column is assigned.

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

' The next line goes into the Declarations section of the module:
' SuppliersProducts is a class derived from DataSet.
Private suppliersProducts As SuppliersProducts 

Private Sub CreateConstraint()
   ' Declare parent column and child column variables.
   Dim parentColumn As DataColumn
   Dim childColumn As DataColumn
   Dim fkConstraint As ForeignKeyConstraint

   ' Set parent and child column variables.
   parentColumn = suppliersProducts.Tables("Suppliers").Columns("SupplierID")
   childColumn = suppliersProducts.Tables("Products").Columns("SupplieriD")
   fkConstraint = New ForeignKeyConstraint( _
       "SuppierFKConstraint", parentColumn, childColumn)

   ' Set null values when a value is deleted.
   fkConstraint.DeleteRule = Rule.SetNull
   fkConstraint.UpdateRule = Rule.Cascade
   fkConstraint.AcceptRejectRule = AcceptRejectRule.Cascade

   ' Add the constraint, and set EnforceConstraints to true.
   suppliersProducts.EnforceConstraints = True
End Sub

.NET Framework
Available since 1.1
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