c# - Error, method not supported by LINQ to Entities

Question

Why I am getting this error:

The method 'Single' is not supported by LINQ to Entities. Consider using the method 'First' instead.

           public ActionResult Details(int id)
Line 27:   {              
             var result = (from d in _db.MovieSet
Line 29:     where d.Id == id
Line 30:     select d).Single();
            //
            //
           } 

Code compiles safe, but only breaks if call is made to the respective section. I am new to LINQ, therefore do not know which methods are for LINQtoSQL or LINQtoEntities. This means more errors! We cannot remember all methods this way.

My question is, if there are limitations to the methods applicable to certain types / scenarios, why do they appear in Intellisense?

EDIT: Any work-around / technique helpful to have an idea if one is supported ?

Answer 1

In the case of LINQtoSQL / Entities, the queries are all broken down into expression trees which are then passed to the provider APIs. The providers cannot provide compile time information about the trees they do or do not support because there is no syntactic difference. The only choice is for them to provide runtime data.

For example once in expression tree form, both the Single and First appear as a MethodCallExpression instance.