HiddenFieldDesigner Class
Assembly: System.Design (in system.design.dll)
In a visual designer, when the user switches from Source to Design view, the markup source code that describes a HiddenField control is parsed and a design-time version of the control is created on the design surface. When the user switches back to Source view, the design-time control is persisted to the markup source code and edited into the markup for the Web page. The HiddenFieldDesigner class provides design-time support for the HiddenField in a visual designer.
The GetDesignTimeHtml method returns the markup that is used to render the associated HiddenField at design time. The Initialize method prepares the designer to view, edit, and design the associated HiddenField.
The following code example shows how to extend the HiddenFieldDesigner class to change the appearance of controls that are derived from the HiddenField control at design time.
The example derives the MyHiddenField control from the HiddenField. The MyHiddenField is a copy of the HiddenField. The example also derives the MyHiddenFieldDesigner class from the HiddenFieldDesigner class and applies a DesignerAttribute attribute for the MyHiddenFieldDesigner on the MyHiddenField control.
The MyHiddenFieldDesigner overrides the GetDesignTimeHtml method to generate a placeholder that includes the Value property in the placeholder, along with the control class name and the ID property.
Imports System Imports System.Web Imports System.Web.UI.WebControls Imports System.Web.UI.Design.WebControls Imports System.ComponentModel Imports System.Security.Permissions Namespace Examples.VB.WebControls.Design ' The MyHiddenField is a copy of the HiddenField. <AspNetHostingPermission(SecurityAction.Demand, _ Level:=AspNetHostingPermissionLevel.Minimal)> _ <AspNetHostingPermission(SecurityAction.InheritanceDemand, _ Level:=AspNetHostingPermissionLevel.Minimal)> _ <Designer(GetType(Examples.VB.WebControls.Design.MyHiddenFieldDesigner))> _ Public Class MyHiddenField Inherits HiddenField End Class ' MyVBHiddenField ' Derive a designer that inherits from the HiddenFieldDesigner. Public Class MyHiddenFieldDesigner Inherits HiddenFieldDesigner ' Generate the design-time markup. Public Overrides Function GetDesignTimeHtml() As String ' Get a reference to the control or a copy of the control. Dim myHF As MyHiddenField = CType(ViewControl, MyHiddenField) Dim markup As String = _ CreatePlaceHolderDesignTimeHtml( _ "Value: """ & myHF.Value.ToString() & """" ) Return markup End Function ' GetDesignTimeHtml End Class ' MyHiddenFieldDesigner End Namespace ' Examples.VB.WebControls.Design
- SecurityPermission for calling unmanaged code. Demand value: Demand. Permission value: UnmanagedCode
System.ComponentModel.Design.ComponentDesigner
System.Web.UI.Design.HtmlControlDesigner
System.Web.UI.Design.ControlDesigner
System.Web.UI.Design.WebControls.HiddenFieldDesigner