This example demonstrates how to filter the ASPxGridView bound to SqlDataSource via the ControlParameter. The ControlParameter is passed to the SqlDataSource from an external ASPxComboBox. The ASPxComboBox is inside TemplateControl. Sometimes it's hard to correctly build the ControlParameter's ControlID property manually, so it's better to build it at runtime. In fact, the ControlParameter's ControlID property equals the UniqueID property of an external ASPxComboBox.