CODEWITHSUNDEEP
c#wcf
PinoyDev
PinoyDev

Reputation: 1047

System.NullReferenceException On WCF call

I'm having quite a difficulty trying to trace this bug. At first I thought it was linq SQL data that's causing NRE because every time I look at the tracer log, it gives me the .cs line 37 which is pointed to my sql (stored proc) call. The reason I suspect this, the result of this sproc is null (not NULL) but there's no row return for all the fields. What I did was to put data on it, and now comes the frustration; I still get the same error. Maybe it's worth mentioning that when I use the WCF as reference(not servicereferences) a DLL straight to bin then it works perfect, only when I try to use the client (mywebservice.client) one.

Any ideas where I should be looking? It is on app.config? Also, I'm using a console app to access the WCF.

This is my code:

public static List<usp_GetPaymentsResult> GetScheduledPayment(DateTime DateRun, int Fee)
    {
        try
        {

            PaymentDataContext DBContext = new PaymentDataContext();
            return DBContext.usp_GetPayments(DateRun, Fee).ToList(); //line 37
        }
        catch (SqlException ex)
        {
            throw ex;

        }
        catch (Exception ex)
        {
            throw ex;
        }
    }

Upvotes: 1

Views: 1440

Answers (2)

Graham Laight
Graham Laight

Reputation: 4840

After a frustrating 30 mins trying to debug a WCF NullReferenceException, turned out I had corrected an error in the WCF method structure, but hadn't refreshed the service in the calling client.

Upvotes: 0

nvoigt
nvoigt

Reputation: 77294

public static List<usp_GetPaymentsResult> GetScheduledPayment(DateTime DateRun, int Fee)
{
   using(var context = new PaymentDataContext())
   {
       var payments = DBContext.usp_GetPayments(DateRun, Fee);

       if (payments == null)
       {
          // bad database! handle error here
       } 

       return payments.ToList();
   }
}

Please note the following:

  • A DBContext is IDisposable. Put it in a using block, or it will not be disposed in a timely fashion.

  • Your exception handling blocks did nothing but trash the exception. If you want to rethrow an exception, use throw; without the variable. It will rethrow the exception. Using the variable ex again will overwrite it's stacktrace and valuable information will be lost. However, as your blocks would have been nothing but rethrowing an exception, you can just not catch it. Same result.

  • Check the result for null before you call an extention method like .ToList() on it.

Finally, WCF Webservices are not magic. You can put breakpoints there and debug them. If you have problems doing so, maybe it would be a good idea to ask a question about that with more details about your webservice setup (VS internal or IIS Express or IIS?) and your project structure. Guessing the error based on line number is so 80s :)

Upvotes: 2

Related Questions