assign nullable objects for returning IQueryable

Question

I am returning IQueryable<Customer> to the other method for some querying operations. The return method looks like:

return from cust in _dbCustList
               select new Customer
               {
                   CustomerId = cust.Customer_Id,
                   FirstName= cust.First_Name,
                   LastName= cust.Last_Name,
                   DOB= cust.Date_Of_Birth,
                   LoginTime = cust.Login_Time ?? new TimeSpan(0, 0, 0);
               };

In the above result, cust.Login_Time is nullable property.

When i try to query the above result, it throws an error:

Method 'System.TimeSpan GetTimeSpan(System.Nullable`1[System.TimeSpan])' has no supported translation to SQL.

How to solve this error?

Answer 1

Why do you use the null- check?

When you remove the null check the written query gets translated into a SQL query and will be executed. Now you have the result you can do any magic you want...

Answer 2

I would query into an anonymous type and then map the result to your business object in-memory:

var q = from cust in _dbCustList
        select new
        {
            cust.Customer_Id,
            cust.First_Name,
            cust.Last_Name,
            cust.Date_Of_Birth,
            cust.Login_Time
        };

return from cust in q.AsEnumerable()
       select new Customer
       {
           CustomerId = cust.Customer_Id,
           FirstName= cust.First_Name,
           LastName= cust.Last_Name,
           DOB= cust.Date_Of_Birth,
           LoginTime = cust.Login_Time ?? TimeSpan.Zero;
       };