This may not be news to some of you, and for you I apologize. For the rest, please avoid using MsgBox in VB .NET projects, and use MessageBox.Show instead.

MsgBox is a wrapper around the MessageBox.Show method and is meant for backwards compatibility with older VB projects. It should be left for those who really can't do without it.

A common misuse for message boxes is debugging code, and most people have invariably found the following code snippet lazing about in production code from time to time:

   Try
      'Some error prone code
   Catch ex as SomeException
      MsgBox(ex)
   End Try

The problem with this 'debugging' code is that in certain circumstances it will cause bugs of its own. Beware of MsgBox throwing exceptions. I'm not referring to just the documented InvalidOperationExceptions either. If the exception does something interesting in its overload of ToString, or if the MsgBox function fails when determining the title of the message box then anything from StackOverFlowExceptions to OutOfMemoryExceptions can occur.

But wait…..there's more, another issue is localisation. If you are using FxCop and have turned on System.Globalization, any call to MessageBox.Show must specify the RTL nature of the box to be shown. The problem with MsgBox is that while it does some fancy work to determine the title, it doesn't bother determining the RTL nature of the parent window. The CA rule doesn't appear to have been written to take calls to MsgBox into consideration. In short, calls to MsgBox break the Globalisation rule CA1300.