Minor User Control Initialization Problem

Ron Howerton · May 4th, 2004, 10:21 AM

I'm having a minor problem in a user control I've written, caused by the fact that the Initialization sequence fires when I drop the control on the form rather than when the form it's on is loading at run time. I assume this is because the IDE needs to fire a Paint event to draw the control in the IDE and this fires the Initilization event. The problem is that this is causing an error in the designer because an object I'm looking for in the initilization code doesn't exist at design time, only at run time. I've wrapped the reference in a try statement which prevents the error from causing serious problems in IDE, so this isn't a big deal.

But I recall there being a state variable you could check in VB6 to see whether the object was being displayed in the IDE GUI at design time or actually running and avoid any user defined initialization except when the code is being run. Does such a variable exist in VB.NET?

Imar · May 4th, 2004, 10:37 AM

Hi Ron,

If your control implements the IComponent interface (which it does when you inherit from Control), you can use this syntax:

Code:

if (this.Site.DesignMode == true)
{
  // Design Mode
}
else
{
  // Run-time
}

I only discovered this recently, and haven't really implemented it yet in my controls (I check for ClientID == null), but I think this should work.

Cheers,

Imar
---------------------------------------
Imar Spaanjaars
Everyone is unique, except for me.
While typing this post, I was listening to: Aqueous Transmission by Incubus (Track 13 from the album: Morning View) What's This?

Ron Howerton · May 4th, 2004, 11:59 AM

That was what I was looking for but...it hasn't fixed the problem. The IDE just does not like bad references and there appears no way to trap for thenm in a user control. Thanks anyway!

Imar · May 8th, 2004, 08:27 AM

Hi Ron,

After playing around with this a bit, I found out that at run-time this.Site does not exist. So, to successfully detect design-time, you'll need something like this:

if (this.Site != null && this.Site.DesignMode == true)
{
// Design Mode
}
else
{
// Run-time
}

With this code, it should be possible to skip the "bad references". That is, declare the variable outside this if block, and assign them a value only in the else clause (run-time).

If this is still an issue for you, can you post some code for us to look at?

Cheers,

Imar
---------------------------------------
Imar Spaanjaars
Everyone is unique, except for me.

Ron Howerton · May 10th, 2004, 07:38 AM

Imar,

Thanks for your follow-up. I did try your original suggestion, but removed this.site because this is a Windows application and I assumed this.site would not therefore exist. However, in the meantime, I've corrected the premature reference so that the problem no longer exists, which is no doubt the right response to this issue to begin with. Thanks again for your assistance.