Custom Exception with Entity Framework and Repository Pattern

Question

I am following this Asp .Net tutorial as a guide:

http://www.asp.net/web-forms/tutorials/continuing-with-ef/using-the-entity-framework-and-the-objectdatasource-control-part-2-adding-a-business-logic-layer-and-unit-tests

I have created a custom error to prevent duplicate records on insert and update

Public Class DuplicateAgencyException
Inherits Exception

Public Sub New(ByVal message As String)
    MyBase.New(message)
End Sub
End Class

I have created a validation method that checks for duplication on insert or update:

Public Sub ValidateAgencyName(ByVal agency As agency_temp)
        If Not IsNothing(agency) Then
            Dim duplicateAgency As agency_temp = AgencyRepository.GetAgencyByName(agency.agency_name).FirstOrDefault()
            If Not IsNothing(duplicateAgency) AndAlso duplicateAgency.agency_id <> agency.agency_id Then
                Throw New DuplicateAgencyException(String.Format("Agency: {0} already exists.", duplicateAgency.agency_name))
            End If
        End If
    End Sub

I run a unit test to insert a record, and purposefully insert a duplicate, and it throws the correct error. Now I need to handle this error with the ObjectDataSource that displays this data, such as OnInserted and OnUpdated, but I can't even get to that point. When I insert a record, I get the error assistant telling me that DuplicateAgencyException was unhandled by user code. Do I need a try...Catch there? (I did try that to no avail).

Luke Baughan Luke Baughan · Accepted Answer · 2012-07-26T21:19:08

I believe you need to wrap your exception within the methods referenced by the events you mention in a try catch block as you suggest. You should wrap the existing code like so

MethodName(params)
《
try 《 /// existing code 

》
catch (ExceptionType ex) 《
/// error handling code
》

》

If you post your event handling code and the aspx i can be more specific. Please excuse any errots wrote this on my phone.

Custom Exception with Entity Framework and Repository Pattern

1 Answers