Export (0) Print
Expand All

How to: Filter Errors in a Catch Block in Visual Basic 

Catch statements provide more than one option for filtering errors. One method for filtering is doing so by types of exception. In such cases, it is important to move from the most specific type of exception to the most general, since the Catch statements are executed in order.

A When clause can also be used to filter on a conditional expression, such as a specific error number. You can combine both approaches as well.

NoteNote

  The options available in dialog boxes, and the names and locations of menu commands you see, might differ from what is described in Help depending on your active settings or edition. This Help page was written with General Development Settings in mind. To change your settings, choose Import and Export Settings on the Tools menu. For more information, see Visual Studio Settings.

To filter on exception type

  • Insert a Catch statement for each type of exception you wish to check, going from the most specific to the most general.

    Try
        Throw New Exception
    Catch ex As System.IO.IOException
        ' Code reacting to IOException 
    Catch ex As System.NullReferenceException
        ' Code reacting to NullReferenceException
    Catch ex As Exception
        ' Code reacting to any exception
    End Try
    
    

To filter on a conditional expression

  • Use a Catch When statement to filter on a conditional expression. If the conditional expression evaluates as True, the code following the Catch block will be executed.

    Try
        ' Code goes here.
        ' Check for type mismatch error.
    Catch ex As Exception When Err.Number = 5
        ' Code reacting to exception. 
    End Try
    
    

See Also

Community Additions

ADD
Show:
© 2015 Microsoft