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HiddenFieldDesigner Class

Provides design-time support in a visual designer for the HiddenField control.

Namespace:  System.Web.UI.Design.WebControls
Assembly:  System.Design (in System.Design.dll)

'Declaration
<SecurityPermissionAttribute(SecurityAction.Demand, Flags := SecurityPermissionFlag.UnmanagedCode)> _
Public Class HiddenFieldDesigner _
	Inherits ControlDesigner
'Usage
Dim instance As HiddenFieldDesigner

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

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0

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