Why does this code generate a NotSupportedException?
c#, linq-to-entities, notsupportedexception
Solution
EDIT: Okay, the code blows up because it doesn't know what to do with the call to `foo()`. The query is built up as an expression tree which is then converted to SQL.
The expression tree translator knows about various things - such as string equality, and various other methods (e.g. `string.StartsWith`) but it doesn't know what your `foo` method does - `foo()` is a black box as far as it's concerned. It therefore can't translate it into SQL.
Problem
Why does this throw System.NotSupportedException? ``` string foo(string f) { return f; } string bar = ""; var item = (from f in myEntities.Beer where f.BeerName == foo(bar) select f).FirstOrDefault(); ``` Edit: Here's an MSDN reference that (kind of) explains things... Any method calls in a LINQ to Entities query that are not explicitly mapped to a canonical function will result in a runtime NotSupportedException exception being thrown. For a list of CLR methods that are mapped to canonical functions, see CLR Method to Canonical Function Mapping. See also http://mosesofegypt.net/post/LINQ-to-Entities-what-is-not-supported.aspx