Question

I have a function that causes an exception in the designer. Can I avoid the call of the function if the designer loads it. Is there an attribute or something that is better than try catch?

Some more details:
I mean the visual studio designer for win forms. My form is using a signleton wich calls LoadProject() on initialize. Now I want to avoid that the designer calls the LoadProject() function.

Answer 1

There are a few ways of detecting whether or not you are in design mode:

• Check the value of the DesignMode property of the control. This does not work in a constructor of a control though, as it only returns true if the control has been sited, which does not happen until after the control has been created. It also has a bug whereby a custom control inside a custom control will always return false
• Check whether the current application’s path contains devenv.exe using Application.ExecutablePath.ToLower().IndexOf("devenv.exe"). If is does, the control is being instantiated by Visual Studio. A bit horrible, but it works.
• Check LicenseManager.UsageMode for the value LicenseUsageMode.Designtime (have a look at my answer to Detecting design mode from a Control’s constructor for more details). Note that this does work in the constructor.

Wrapping the call to your function in any of these checks should solve your problem.