Assembly: System.Data (in system.data.dll)
/** @property */ public Rule get_DeleteRule () /** @property */ public void set_DeleteRule (Rule value)
Property ValueOne 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.Tables("Suppliers").Constraints.Add(fkConstraint) suppliersProducts.EnforceConstraints = True End Sub
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The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.