AOP with PostSharp: Listing 1.

A simple error-handling aspect

Module Module1
  Sub Main()
    Try
      Call CreateError()
      Trace.WriteLine("OnExceptionAspect_Demo: Returned from CreateError")
    Catch ex As Exception
      Trace.WriteLine("")
      Trace.WriteLine("An Application Error Ocurred. " & ex.Message)
    End Try
  End Sub

   <ExceptionWrapper() >
  Sub CreateError()
    Dim zero As Integer = 0
    Dim DivByZero As Integer = 10 / zero
    Trace.WriteLine("Numerator Divided by Zero:", DivByZero.ToString)
  End Sub

   <Serializable() >
  Public Class ExceptionWrapper
    Inherits PostSharp.Aspects.OnExceptionAspect
    Public Overrides Sub OnException( _
      args As PostSharp.Aspects.MethodExecutionArgs)
      Dim ErrorID = Guid.NewGuid
      Dim TraceMsg1 = String.Format("PostSharp: Error ID = {0}", ErrorID)
      Dim TraceMsg2 = String.Format( _
        "PostSharp: {0} had an error at {1} of type {2}",
        args.Method.Name, DateTime.Now, args.Exception)
      Trace.WriteLine("PostSharp Detected An Application Error")
      Trace.WriteLine(TraceMsg1)
      Trace.WriteLine(TraceMsg2)
      Trace.WriteLine("")
      Dim ExceptionMsg = String.Format( _
        "Please contact support with Error ID: {0}", ErrorID)
      Throw New Exception(ExceptionMsg, innerException:=args.Exception)
    End Sub
  End Class
End Module

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 joekunk@ajboggs.com.