如何区分用户控件在窗体上加载和运行时加载

Question

I created a user control using C# for windows form application. This user control has some properties. In runtime, if the user does not enter values for this properties I want to show a message box and exit the application.

The problem is when I write the checking code in the Load event of User Control. When I drag & drop it on the form the message box will appear.

private void UserControl1_Load(Object sender, EventArgs e) 
{
    if (_getFirstPageArgument==null || _getFirstPageArgument.Length==0) 
    { 
        throw new Exception("Some Message"); 
    }
}

How do I distinguish between load on the form and load on run time?

Answer 1

I fear there is a larger problem here. But to solve your immediate problem (if I understand correctly...) There is a form attribute called DesignMode . When you are in the visual studio design mode, this will be true . At runtime, this will be false .

Answer 2

For beginners, @Nimas case can be a good study point to understand that Visual Studio actually runs and executes parts of our code even when we are in design time, which is why the constructor is invoked. Even "DesignMode" property is not 100% reliable. You can find an interesting note here related to that http://weblogs.asp.net/fmarguerie/archive/2005/03/23/395658.aspx

Answer 3

If you only want to know when the type itself has been loaded into the runtime (not a specific instance), you can put code into the static constructor for that class.

If I'm misinterpreting your question, please clarify using a timeline when you want specific events to happen.