Strange Linq to Entities Behavior with AsExpandable()

Question

Consider the following `Person` entity: ``` public class Person { public int Id { get; set; } public string FirstName { get; set; } public string LastName { get; set; } } ``` Using the following `Expression` (constructed using `PredicateBuilder`) as the criteria: ``` var byName = PredicateBuilder.True().And(x => x.FirstName == "Chaim"); ``` When invoked using the following syntax, the generated SQL is fine (includes the `WHERE` statement): ``` ctx.Set().AsExpandable().Where(x => byName.Invoke(x)); ``` However, when invoked using this slightly different syntax, no SQL `WHERE` is involved and the filtering is being done by `Enumerable.Where` instead: ``` ctx.Set().AsExpandable().Where(byName.Invoke); ``` Any thoughts?

Accepted Answer

There is no implicit conversion from a method group to an `Expression` (of a corresponding delegate type). There is an implicit conversion from a method group to a delegate of a matching signature. Therefore only the `IEnumerable` overload matches. Of course, that's not to say that you need to use a lambda. Just write: ``` ctx.Set().AsExpandable().Where(ByName); ``` Since you're passing in an expression (`ByName` is, after all, an `Expression` already, which is exactly what `Queryable.Where` requires) this will evaluate as a query, not in linq to objects.

Strange Linq to Entities Behavior with AsExpandable()

Solution

Problem