Assembly: System.Data.Entity (in System.Data.Entity.dll)
There are various ways to get an invalid entity. The most common scenario is when an Entity SQL query uses the TREAT operator to interpret an instance of a polymorphic type as a particular type, and the instance in question does not match. (TREAT is similar to the C# as operator). In this case, the query returns an entity that is not valid, and the entity key of the resulting entity is set to .