Assembly: System.Design (in system.design.dll)
In a visual designer, when you switch from Source to Design view, the markup source code that describes the Button control is parsed and a design-time version of the control is created on the design surface. When you switch back to Source view, the design-time control is persisted to the markup source code and edited into the markup for the Web page.
This section provides two code examples. The first demonstrates how to extend the ButtonDesigner class. The second demonstrates how to extend the Button class and associate it with the class that is created in the first code example.
The following code example shows how to create a custom designer class that extends the ButtonDesigner class and overrides the GetDesignTimeHtml method. If the BorderStyle property has not been set previously (that is, it has the NotSet field value), a call to the GetDesignTimeHtml method sets it to a blue-dashed border with a width of three pixels, and then displays that border on the design surface. If the BorderStyle property has been set, the existing border property values are displayed.
' Create a class that derives from ButtonDesigner ' and displays the custom SampleButton control ' on the design surface. Imports System Imports System.Web.UI.Design Imports System.Drawing Imports System.ComponentModel Imports System.Web.UI.WebControls Imports System.Web.UI.Design.WebControls Namespace Examples.AspNet Public Class SampleButtonDesigner Inherits ButtonDesigner ' Override the GetDesignTimeHtml method. Public Overrides Function GetDesignTimeHtml() As String Dim sampleButton As SampleButton = CType(Component, SampleButton) Dim designTimeHtml As String = Nothing ' Check the control's BorderStyle property ' to conditionally render design-time HTML. If (sampleButton.BorderStyle = BorderStyle.NotSet) Then ' Create variables to hold current property settings. Dim oldBorderStyle As BorderStyle = sampleButton.BorderStyle Dim oldBorderWidth As Unit = sampleButton.BorderWidth Dim oldBorderColor As Color = sampleButton.BorderColor ' Set properties and the design-time HTML. Try sampleButton.BorderStyle = BorderStyle.Dashed sampleButton.BorderWidth = Unit.Pixel(3) sampleButton.BorderColor = Color.Blue designTimeHtml = MyBase.GetDesignTimeHtml() ' If an exception occurs, call the GetErrorDesignTimeHtml ' method. Catch ex As Exception designTimeHtml = GetErrorDesignTimeHtml(ex) ' Return properties to their original settings. Finally sampleButton.BorderStyle = oldBorderStyle sampleButton.BorderWidth = oldBorderWidth sampleButton.BorderColor = oldBorderColor End Try Else designTimeHtml = MyBase.GetDesignTimeHtml() End If Return designTimeHtml End Function End Class End Namespace
The following code example shows how to use a simple class that extends the Button class and is associated with the SampleButtonDesigner class, created in the preceding example, through the DesignerAttribute object.
Windows 98, Windows 2000 SP4, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.