AOP with PostSharp: Listing 2.

Handling selected exceptions in the aspect

Aspect-Oriented Programming
' <ExceptionWrapper() >
' <ExceptionWrapper(HandleExceptionSingleType:=GetType(OverflowException)) >
' <ExceptionWrapper(HandleExceptionSingleType:=GetType(DivideByZeroException)) >
' <ExceptionWrapper(HandleExceptionTypeArray:={GetType(OverflowException), _ 
  GetType(DivideByZeroException)}) >

Public Property HandleExceptionTypeArray As Type()
Public Property HandleExceptionSingleType As Type

Public Overrides Function GetExceptionType( _
  targetMethod As System.Reflection.MethodBase) As System.Type
  Dim result As Type = Nothing
  Dim MethodExceptionType = MyBase.GetExceptionType(targetMethod)
  'If no explict exception types specified, handle any type of exception
  If IsNothing(HandleExceptionSingleType) AndAlso IsNothing( _
    HandleExceptionTypeArray) Then
    result = MethodExceptionType
    'If there is a named single exception type and it is a match, handle it
    If IsNothing(HandleExceptionSingleType) = False AndAlso _
      HandleExceptionSingleType = MethodExceptionType Then
      result = MethodExceptionType
    End If

    'If there is an array of exception types, and not already a match,
    'handle the exception if any in the array are a match
    If IsNothing(HandleExceptionTypeArray) = False AndAlso IsNothing(result) = True Then
      For Each testType In HandleExceptionTypeArray
        If testType = MethodExceptionType Then
          result = MethodExceptionType
        End If
    End If
  End If

  'Will be nothing only if types specified and no match
  Return result
End Function

About the Author

Joe Kunk is a Microsoft MVP in Visual Basic, three-time president of the Greater Lansing User Group for .NET, and developer for Dart Container Corporation of Mason, Michigan. He's been developing software for over 30 years and has worked in the education, government, financial and manufacturing industries. Kunk's co-authored the book "Professional DevExpress ASP.NET Controls" (Wrox Programmer to Programmer, 2009). He can be reached via email at [email protected].

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