When using an operation like the Where() method in the following code:

Listing 8

_context.Customers.Where(i => i.AccountNumber == "T2341003");

The results that come back are a DataQuery object. This object is not null for queries that even return no results. So the following code works:

Listing 9

customers = _context.Customers.Where(i => i.AccountNumber == "XXXX");
Assert.AreEqual(0, customers.Count());
 
count = 0;
foreach (Customer customer in customers)
{
      count++;
      //Test that iterating through collection is OK
}
Assert.AreEqual(0, count);

What this means is that the Where() method returns no records, because the account number does not exist. The result count is an empty query, but you can continue to use this object freely, as shown above, and not have to worry about a null reference exception.