Question

There are two DLLs, A and B, in A.DLL there is a form class like this:

namespace AAA
public class AForm: Form
{
  ...
  private void btnOK_Click(object sender, EventArgs e)
  {
      DoSomeSth();
  }
}

In B.DLL, there is some code like this

try
{
   AForm dlg = new AAA.AForm();
   dlg.ShowDialog();    
}
catch(Exception ex)
{
   MessageBox.Show(ex.Message);
}

There will be exception in the function DoSomeSth after OK button is clicked
When I debug the code using vs2005, the exception could be caught in B.DLL, but if I ran the application directly without debug, the exception won’t be caught in B.DLL, what is the reason?

Answer 1

This is a known issue. According to the KB article:

When you run your Windows Forms
application without using the
debugger, you use the
NativeWindow.CallBack method to catch
the exception and to prevent the
program from unexpectedly quitting
(crashing). In the
NativeWindow.CallBack method, you
populate the exception message by
using a standard exception dialog box.

However, if you run your Windows Forms
application with the debugger, you do
not catch the exception because you
use the
NativeWindow.DebuggableCallBack
method. When you use the
NativeWindow.DebuggableCallBack
method, the just-in-time (JIT)
debugger stops the application from
running.