Handling Errors in a nice way depending on the type of error.

tarekahf posted on Thursday, August 11, 2011

In the UI Code (ASPX), I want to write proper error handling code to display the error in a nice way depending on the error type.

In my case, I see the errors has two main categories:

1. Unexpected errors which you need to dump the full "ex.StackTrace" and this will look very ugly, but is needed so that the developer can locate the source of the error in the code.

2. Expected errors such as incorrect data in a field or record not found ...etc. Such errors are controlled and I will display a nice error message to the user with full details to help resolve the problem. In this case, I only need to display a one-line error without any other details.

Why I am asking for this? This is becuase I realized that any error thrown from the Business Object / Data Access Part, it will always be "DataPortalException". Sometimes, when there is an expected error while in "Data Access" part, I will throw a predefined exception, say eHRMDException(), with custom message. But I find difficulty in catching this error on the UI part, and I want to make sure I am doing the right thing.

I am using the following code template, and I need you help to tell me if this is OK (see the DataPortalException):

 

        Try

            theStaffID = Request.QueryString("StaffID")

            If SPMSForm.Exists(theStaffID) Then

                theSPMSForm = SPMSForm.GetSPMSForm(theStaffID)

            Else

                theSPMSForm = SPMSForm.NewSPMSForm(theUserCtrlInfoPack)

            End If

            SaveSPMSFormToSession(theSPMSForm)

            theSPMSForm.RenderPDFForm(Response, GetWebRoot, Page.Server.MapPath(".\"))

            Response.End()

        Catch ex As System.Security.SecurityException

            GetMaster.ErrMsg = ex.Message

            ClearMedicalCardFormSession()

        Catch ex As eHRMDException

            GetMaster.ErrMsg = ex.Message

            ClearMedicalCardFormSession()

        Catch ex As Csla.DataPortalException

            If Not ex.BusinessException Is Nothing AndAlso TypeOf (ex.BusinessException) Is eHRMDException Then

                GetMaster.ErrMsg = ex.BusinessException.Message

            Else

                GetMaster.ErrMsg = ex.Message & "<br>" & ex.StackTrace

            End If

            ClearMedicalCardFormSession()

        Catch ex As Exception

            GetMaster.ErrMsg = ex.Message & "<br>" & ex.StackTrace

            ClearMedicalCardFormSession()

        End Try

 

In the above code, I am checking the type of the BusinessException, and if it is "eHRMDException" which is the custom error I generated, then I will only display the error message as one line, otherwise, I will display the complete StackTrace().

 If you have any comment or suggestion to do it in a better way, please let me know.

Tarek.