The method 'Where' cannot follow the method 'Select' or is not supported

Question

Why am I getting:

The method \'Where\' cannot follow the method \'Select\' or is not supported. Try writing the query in terms of supported methods

Answer 1

It's because whatever query provider you are using isn't able to handle this. It's not invalid in the general case; in fact most query providers do support filtering after projecting. Certain query providers simply aren't as robust as others, or they are representing a query model that is less flexible/powerful than the LINQ interface (or both). As a result, LINQ operations that are correct from the C# compiler's point of view might still not be translatable by the query provider, so the best it can do is throw an exception at runtime.