ButtonDesigner.GetDesignTimeHtml Method

public:
 override System::String ^ GetDesignTimeHtml();

public override string GetDesignTimeHtml ();

override this.GetDesignTimeHtml : unit -> string

Public Overrides Function GetDesignTimeHtml () As String

Returns

A String containing the markup used to render the Button at design time.

Examples

The following code example demonstrates how to override the GetDesignTimeHtml method to change the generated markup.

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.

Typically, the GetDesignTimeHtml calls its base method, ControlDesigner.GetDesignTimeHtml, which calls into the Control.RenderControl method of the associated control to generate the markup.

' Create a class that derives from ButtonDesigner
' and displays the custom SampleButton control
' on the design surface.
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

Remarks

The GetDesignTimeHtml method replaces the Text property with the ID property of the Button control if the Text contains no displayable characters. Then, the GetDesignTimeHtml method calls its base method, ControlDesigner.GetDesignTimeHtml, which calls into the Control.RenderControl method to generate the markup.

Notes to Inheritors

If you are overriding the GetDesignTimeHtml() method, typically you will modify selected property values, then call the base method to generate the markup, and then restore the properties to their original values.

Applies to

See also

• Button
• GetDesignTimeHtml()
• RenderControl(HtmlTextWriter)
• Introduction to ASP.NET Control Designers
• Walkthrough: Creating a Basic Control Designer for a Web Server Control