It seams all you want to do is filter your context.Books by some criteria. IEnumerable<Book> books = context.Books.Where(b => someConditions); If you still need the empty IEnumerable you can just call Enumerable.Empty(): IEnumerable<Book> books = Enumerable.Empty<Book>();
Just decompile the code to work out what’s going on. string.Format(“{0}”, null) calls the most specific applicable overload, which is string.Format(string, object[]). The overloads of string.Format are: Format(String, Object) Format(String, Object[]) Format(IFormatProvider, String, Object[]) Format(String, Object, Object) Format(String, Object, Object, Object) Hopefully it’s obvious why the last three options are invalid. To work out which … Read more
You are using yield return. When doing so, the compiler will rewrite your method into a function that returns a generated class that implements a state machine. Broadly speaking, it rewrites locals to fields of that class and each part of your algorithm between the yield return instructions becomes a state. You can check with … Read more