I have a custom web server control that consists of three dropdowns.  I am trying to override the Width property and set it to a default width of 128 pixels.  The property is defined as follows:

In the New method I set mWidth to Unit.Pixels(128).  Originally I tried DefaultValue(Unit.Pixels(128)) in the attribute of the property because that made more sense than putting the string "128px" but the compiler complained.  I'm obviously doing something wrong, any ideas?

Thanks, Robb

Try setting the attribute this way

DefaultValue(GetType(Unit), "128px")

By the way does mWidth itself depend on child controls or do child controls use that value? I'm just wondering as mWidth is not directly accessing any subcontrol's property, that does it need the child control creation (as child controls are created before returning or setting the value). Anyways, that wasn't what you asked but I just noticed.

Well the compiler doesn't complain now with DefaultValue(GetType(Unit), "128px") but it's still not setting the initial width of the control.  Maybe I'm missing something here.  Oh, and to answer your question on mWidth it is just the protected local value behind the public property for width.  Not really sure if I need the EnsureChildControls or not because I'm not really setting the width of the individual elements (the three selects) I'm just trying to set the width of the "rendered" web control.  And what is odd is that if you switch from design to html and back it shows up.  BTW the width is 132 for some odd reason.

And you said that you set it yourself in constructor?

Here's the constructor:

Public Sub New()

End Sub

And here's the designer:

Namespace Design
    Public Class TPLDesigner
        Inherits System.Web.UI.Design.ControlDesigner

        Public Overrides Function GetDesignTimeHtml() As String
            Dim sw As New StringWriter
            Dim tw As New HtmlTextWriter(sw)
            Dim cControl As TimePickList = CType(Component, TimePickList)
            cControl.EnsureChildControls()
            cControl.RenderControl(tw)
            Return sw.ToString()
        End Function
    End Class
End Namespace

And here's the attributes line of the control class:

<Designer("Design.TPLDesigner", "Design"), Description("Control to select time of day in 15 minute increments"), DefaultProperty("TimeString"), ToolboxData("<{0}:TimePickList runat=server></{0}:TimePickList>")> _
Public Class TimePickList

I guess that I'm a little confused as to how you're using mWidth in either CreateChildControls or during rendering of the control and also what it is you mean when you say that the value you set (128px) in the constructor does not "show up" - do you mean in the property grid in design mode or in being able to set the total width of the custom control? Are you overriding the Width property because you don't want the user to be able to change it? If so, I'd go this route:

Have you tried this route (I'm assuming your deriving your custom control from WebControl or one of its derivatives so that it has a Width property):

In constructor:
   MyBase.Width=Unit.Pixel(128)

In property:
   <Browsable (False)> _
   Public Overrides Property Width() As Unit
      Get
         Return Me.Width
      End Get
     Set
         'disable setter so that it width cannot be changed
     End Set
   End Property

I'm trying to limit the width to 128px.  So I want them to be able to go below 128 but not above.  Which brings up the question of how do you do comparisons on Unit types?  Obviously the code:

if Mybase.width > "128px" then

doesn't work.

Now that I've thought about this more, it doesn't make sense to use a local var mWidth, I should just reference myBase.Width like you show.  So now that I've changed the constructor to MyBase.Width=Unit.Pixel(128), dragging it into the form shows a 128px wide, blank box.  Again if I switch to html view then back to design my "inner" controls show up.  So a 128px blank box is better than what I was getting before but not sure why the inner controls aren't showing up initially.  Also if I just increase the width a little by dragging in the designer, the inner controls appear.

Thanks for all the help,

Robb

To compare unit types (for pixels only), use the Unit.Value property which returns a double giving the value in pixels.  With this in mind and desiring a lower limit of 128 px wide, you might change the Width property to:

Public Property Width As Unit
   Get
      Return Me.Width
   End Get
   Set (ByVal Value As Unit)
      If Value.Value<128.0 Then Value=Unit.Pixels(128)
      MyBase.Width=Value
   End Set
End Property

As far as the inner controls not showing up initially in the designer, I've seen this happen before when I have not forced the control to recreate its children and rerender after any change has been made.  The following techniques have helped prevent this:

1. Override the Controls property of your custom control to force an EnsureChildControls each time the Control property is referenced:

Public Overrides ReadOnly Property Controls() As ControlCollection
   Get
      EnsureChildControls()
      Return MyBase.Controls
   End Get
End Property

2. In the setter of any property that would change the number of, types of, order of, etc. child controls, set the value of ChildControlsCreated to FALSE.

3. In your custom designer's GetDesignTimeHTML method, reference the custom controls child collection.  Since you have included EnsureChildControls in the overriden Controls property, this should force a recreation of child controls and a re-rendering. Here's an example from one of my control's designers:

Public Class FieldDesigner
   Inherits System.Web.UI.Design.ControlDesigner

   Public Overrides Function GetDesignTimeHtml() As String
      Dim DesignTimeHtml As String
      Dim ControlToDesign As BaseField = CType(Component, BaseField)
      Dim Controls As ControlCollection = ControlToDesign.Controls     'Reference Controls to force rerendering
      DesignTimeHtml = MyBase.GetDesignTimeHtml()
      If DesignTimeHtml.Length = 0 Then DesignTimeHtml = GetEmptyDesignTimeHtml()
      Return DesignTimeHtml
   End Function
End Class

Again thanks for the help.

The width is now working as expected, however the controls still don't get drawn until I "touch" the control ie - start to grow or shrink it, or switch back and forth to design/html.

I basically implemented your designer.  Now do I need to override the GetEmptyDesignTimeHtml also?