I create my own control with some image property. It
works fine when I set or change some images into this
property through Properties Window at Design time. The
problem is I can't set it to None or nothing at Design
time like when set none by hitting Delete button in the
image in properties window in Label control. Does it has
to declare something or I do something wrong

The easiest way is to simply create a subroutine (doesn't have to be
public) named "Reset<propertyname>" that sets your property value back to
Nothing.  For instance:

    Private m_MyImage As Image
    Public Property MyImage() As Image
        Get
            Me.BackgroundImage
        End Get
        Set(ByVal Value As Image)
            Me.BackgroundImage = Value
        End Set
    End Property

    Private Sub ResetMyImage()
        Me.BackgroundImage = Nothing
    End Sub

If you add this and recompile your control, then go back to the property
browser.   Find your property name ("MyImage" in the example above), and
right-click on the left-hand column, over the name of the function.  You
should see a context menu with two options: "Reset" and "Description".  
Click "Reset" (which originally would have been disabled - it should be
enabled now that you added your ResetMyImage function), and the MyImage
property will get reset back to Nothing (or whatever your ResetMyImage
function causes to happen will happen).

For more information, take a look at

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpre...
frlrfsystemcomponentmodelpropertydescriptorclassresetvaluetopic.asp
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpgu...
l/cpconenhancingdesign-timesupport.asp

--
Stephen Weatherford, VB .NET Team
This posting is provided "AS IS" with no warranties, and confers no rights.

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| Subject: Set Nothing to user-defined Image property through Properties
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| Date: Wed, 19 Mar 2003 02:47:49 -0800
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| I create my own control with some image property. It
| works fine when I set or change some images into this
| property through Properties Window at Design time. The
| problem is I can't set it to None or nothing at Design
| time like when set none by hitting Delete button in the
| image in properties window in Label control. Does it has
| to declare something or I do something wrong
|