Question

How can I catch an inner exception in .NET? I need to check 2 databases for a record. The database code throws an exception if a record is not found, so then I want to check the second database:

Try
     # Code to look in database 1
Catch ex as DataServiceQueryException
     Try
          # Code to look in database 2
     Catch ex2 as DataServiceQueryException
          throw New DataServiceQueryException(ex.Message, ex2) # Fails here
     End Try
Catch ex as Exception # Why doesn't ex2 land here?
   # Tell user that data was not found in either database
End Try

The above pseudo-code fails at 'Fails here and ex2 never is handled by my code.

How should I properly handle the inner exception?

Answer 1

The reason your current code doesn’t work is that once you enter the catch section, you’ve already left the try block. Instead, do it like this:

Try
   ''# Check Database 1
Catch
    Try
        ''# Check Database 2
    Catch
         ''# Tell the user that data was not found in either database
    End Try
End Try

Or like this:

Dim FoundFlag as Boolean = False
Try
    ''# Check Database 1
    FoundFlag = True
    ''# Best if you can just return "False" and avoid the exception altogether
Catch
End Try

If Not FoundFlag Then
    Try
        ''# Check Database 2
        FoundFlag = True
    Catch
    End Try
End If

If Not FoundFlag Then
     ''# Tell the user that data was not found in any database
End If