Crystal Report and LINQ

Question

I am using Crystal Report for creating a report. I have two tables, Driver_Specifications and WatchRow.

Primary key of WatchRow is foreign key of Driver_Specifications. I set some field in my report file to show the data of Driver_Specifications and I want to show a specific field of WatchRow instead of the foreign key of Driver_Specifications. What is the query of LINQ for this problem?

This is what I have so far:

var q = (from d in taxi_AgencyDataSet.Driver_Specifications
         orderby d.First_Name, d.ID_Driver
         select new
         {
             d.First_Name,
             d.Last_Name,
             d.Car_Name,
             d.Car_Color,
             d.WatchRow.Watch_Name,
             d.ID_Watch
         }).ToList();

I get the following error:

Object reference not set to an instance of an object

Answer 1

You need to check for null when accessing d.WatchRow to avoid throwing a NullReferenceException:

var q = (from d in taxi_AgencyDataSet.Driver_Specifications
         orderby d.First_Name, d.ID_Driver
         select new
         {
             d.First_Name,
             d.Last_Name,
             d.Car_Name,
             d.Car_Color,
             Watch_Name = d.WatchRow == null ? "None" : d.WatchRow.Watch_Name,
             d.ID_Watch
         }).ToList();