.net - DesignMode with nested Controls

Question

Has anyone found a useful solution to the DesignMode problem when developing controls?

The issue is that if you nest controls then DesignMode only works for the first level. The second and lower levels DesignMode will always return FALSE.

The standard hack has been to look at the name of the process that is running and if it is "DevEnv.EXE" then it must be studio thus DesignMode is really TRUE.

The problem with that is looking for the ProcessName works its way around through the registry and other strange parts with the end result that the user might not have the required rights to see the process name. In addition this strange route is very slow. So we have had to pile additional hacks to use a singleton and if an error is thrown when asking for the process name then assume that DesignMode is FALSE.

A nice clean way to determine DesignMode is in order. Acually getting Microsoft to fix it internally to the framework would be even better!

Answer 1

Revisiting this question, I have now 'discovered' 5 different ways of doing this, which are as follows:

System.ComponentModel.DesignMode property

System.ComponentModel.LicenseManager.UsageMode property

private string ServiceString()
{
    if (GetService(typeof(System.ComponentModel.Design.IDesignerHost)) != null) 
        return "Present";
    else
        return "Not present";
}

public bool IsDesignerHosted
{
    get
    {
        Control ctrl = this;

        while(ctrl != null)
        {
            if((ctrl.Site != null) && ctrl.Site.DesignMode)
                return true;
            ctrl = ctrl.Parent;
        }
        return false;
    }
}
public static bool IsInDesignMode()
{
    return System.Reflection.Assembly.GetExecutingAssembly()
         .Location.Contains("VisualStudio"))
}

To try and get a hang on the three solutions proposed, I created a little test solution - with three projects:

• TestApp (winforms application),
• SubControl (dll)
• SubSubControl (dll)

I then embedded the SubSubControl in the SubControl, then one of each in the TestApp.Form.

This screenshot shows the result when running.

This screenshot shows the result with the form open in Visual Studio:

Conclusion: It would appear that without reflection the only one that is reliable within the constructor is LicenseUsage, and the only one which is reliable outside the constructor is 'IsDesignedHosted' (by BlueRaja below)

PS: See ToolmakerSteve's comment below (which I haven't tested): "Note that IsDesignerHosted answer has been updated to include LicenseUsage..., so now the test can simply be if (IsDesignerHosted). An alternative approach is test LicenseManager in constructor and cache the result."