Question

My search result becomes case sensitive when I change var to IEnumerable; consider below code:

the code below returns both cases with RA or ra:

var result = from x in dataBase.tableName 
             select x;
result = result.Where(x => x.id.Contains("ra"));

the code below returns only cases with ra and not RA:

IEnumerable result = from x in dataBase.tableName 
                     select x;
result = result.Where(x => x.id.Contains("ra"));

Could someone help and explain me what is going on? shouldn’t the result be similar?

Answer 1

The difference is that in the first case, var will be an IQueryable<T> – which means your Where call will be to Queryable.Where (after converting your lambda expression to an expression tree). The filter ends up being executed in the database, where I suspect your field is case-insensitive (and so searching is case-insensitive).

In the second case, you’ve got an IEnumerable<T>, so your Where call will be to Enumerable.Where (after converting your lambda expression to a delegate). The filter ends up being executed in .NET code instead – where Contains is always case-sensitive.

Basically, LINQ is a leaky abstraction – yes, it would be lovely if the same filter gave the same results in all situations, but that’s unrealistic. Learn where the leaks are, and act accordingly – LINQ is still a huge boon 🙂