Default Value of Nothing for Property of type System.Drawing.Image

Hi Everyone,

Hopefully "vb.syntax" is the correct group for this question...

I'm writing a UserControl that exposes a property of the type System.Drawing.Image, like this:

Public Property DefaultImage() As Image
Get
Return propDefaultImage
End Get
Set(ByVal Value As Image)
propDefaultImage = Value
SetImage()
End Set
End Property

The property behaves *mostly* as expected. What I'm having trouble with is the behavior of the property at design-time. I would like to accomplish two things:

1) When my control is placed on a form, in the property browser, my DefaultImage property value is shown to be "(none)". This is correct, except it is appearing in a bold font as if the value has been changed from the default value. When the value is "(none)" I would like it to not be bold.

2) When the developer defines the image by clicking the "..." browse button and selecting a bitmap, all is well: the image is set and everything does what was intended. However, in the property browser, if the developer selects the property value and presses the [del] button on the keyboard, the image is not removed. I would like this to occur.

If you look at the BackgroundImage property of a Form, you can see the behavior I am trying to emulate. I *thought* the solution would just be to define the DefaultValue() attribute for the property to be Nothing, like this:

<DefaultValue(Nothing)> _
Public Property DefaultImage() As Image
....

DefaultValue() is overloaded 11 times and one of the possible arguments is Object, so I figured Nothing would fit for that one. But it does not: "Overload resolution failed...". I then tried all sorts of things like this:

Dim NothingImage As System.Drawing.Image = Nothing

<DefaultValue(NothingImage)> _
Public Property DefaultImage() As Image
....

but I can't do that because DefaultValue() requires a constant. I can't have a constant be an object, so... I'm stuck. There's got to be something obvious that I'm missing. Any ideas?


Thank you for your help!!

Eric



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