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.NET Forum / ASP.NET / Building Controls / October 2006

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Web derived controls in VS2005 designer view

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postings@alexshirley.com - 23 Mar 2006 11:54 GMT
Hi

I'm more or less desperate here, I've posted this in a few forums now
over the months and got absolutely no response. It would be very much
appreciate that you could help in any way here... So take pity :)

I have a control derived from a drop down list written in VB.NET
(ASP.NET 2.0) that dynamically displays listitems retrieved from an SQL
server database. My code works fine but when I go to designer view in
Visual Studio 2005 it renders a gray box displaying: "Error Creating
Control - MyDropDownList, object reference not set to an instance of an
object". Note the drop down list works perfectly when being displayed
in IE.

If I remove my code retrieving the values from SQL server and put in
static values like this:
----------------------------------------------------
Me.Items.Add(New ListItem("Select a Value", "0"))
Me.Items.Add(New ListItem("Test", "1"))
----------------------------------------------------

...the drop down list will render in both the designer and IE. So I am
assuming that the VS2005 designer view will not render dynamic
listitems, but will render static listitems from dropdownlists.

In order to solve this problem I've looked at using:
Protected Overrides Sub Render(ByVal writer As
System.Web.UI.HtmlTextWriter)

...to see if I can force rendering in the design view but no joy at
all, so my approach isn't working here.

I don't really care if the designer renders the exact values from the
database, a couple of dummy values will do if necessary. I just want to
see the control is designer view.

So please - any words of wisdom!

Many thanks indeed...

Alex
Steve C. Orr [MVP, MCSD] - 23 Mar 2006 22:36 GMT
IF Me.DesignMode = True THEN
   'Use Static Values
   Me.Items.Add(New ListItem("Select a Value", "0"))
   Me.Items.Add(New ListItem("Test", "1"))
ELSE
   'get from SQL Server
END IF

Signature

I hope this helps,
Steve C. Orr, MCSD, MVP
http://SteveOrr.net

> Hi
>
[quoted text clipped - 37 lines]
>
> Alex
ovalsquare - 31 Mar 2006 03:07 GMT
Alex,

Did this solve it for you? As I've got the same problem and Steve's
solution does not fix the issue (still get the error in design view).

Ted

> IF Me.DesignMode = True THEN
>     'Use Static Values
[quoted text clipped - 50 lines]
> >
> > Alex
postings@alexshirley.com - 18 Apr 2006 11:10 GMT
Hi Oval

No it didn't unfortunately (thanks for trying Steve).
I see the logic in the code, and I can't see why it doesn't work.
Please let me know if you get any further than I did (is this a VS2005
IDE bug?).

Thanks

Alex
Alex Shirley - 20 Sep 2006 11:52 GMT
Hi

Was there ever a solution to this, is designmode broken?

Many thanks!

Alex
postings@alexshirley.com - 06 Oct 2006 10:52 GMT
Anybody? (one last go before I fizzle out :)

Thanks

Alex

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