ForeignKeyConstraint.DeleteRule ForeignKeyConstraint.DeleteRule ForeignKeyConstraint.DeleteRule ForeignKeyConstraint.DeleteRule Property

Definición

Obtiene o establece la acción que se produce en esta restricción cuando se elimina una fila.Gets or sets the action that occurs across this constraint when a row is deleted.

public:
 virtual property System::Data::Rule DeleteRule { System::Data::Rule get(); void set(System::Data::Rule value); };
[System.Data.DataSysDescription("ForeignKeyConstraintDeleteRuleDescr")]
public virtual System.Data.Rule DeleteRule { get; set; }
member this.DeleteRule : System.Data.Rule with get, set
Public Overridable Property DeleteRule As Rule

Valor de propiedad

Uno de los valores de Rule.One of the Rule values. De manera predeterminada, es Cascade.The default is Cascade.

Ejemplos

En el ejemplo siguiente se crea una ForeignKeyConstraint, se establecen varias de sus propiedades y se agrega DataTable a un ConstraintCollectionobjeto.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

Comentarios

Cuando se elimina una fila de una tabla primaria, el DeleteRule determina lo que ocurrirá en las columnas de la tabla o tablas secundarias.When a row is deleted from a parent table, the DeleteRule determines what will happen in the columns of the child table (or tables). Si la regla está establecida en Cascade, se eliminarán las filas secundarias.If the rule is set to Cascade, child rows will be deleted.

Si se establece SetNullen DBNull , se colocará en las columnas correspondientes de las filas afectadas.If set to SetNull, a DBNull will be placed in the appropriate columns of the affected rows. Dependiendo del origen de datos, se puede permitir o no un valor null en una columna.Depending on your data source, a null value may or may not be permitted in a column. Por ejemplo, SQL Server permite encontrar varios valores NULL en una columna de clave principal, incluso si no son únicos.For example, SQL Server allows multiple null values to be found in a primary key column, even if they are not unique. En, sin embargo, si la DataColumn propiedad de Unique un objeto está establecida trueen, no se permiten varios valores NULL en las columnas de clave principal. DataTableIn a DataTable, however, if a DataColumn object's Unique property is set to true, multiple null values are not allowed in primary key columns.

Si se establece SetDefaulten, se asigna el valor predeterminado de la columna.If set to SetDefault, the default value for the column is assigned.

Se aplica a