What is Type Erasure (Java) vs Reified Generics (C#)?

Java generics are primarily implemented using type erasure: generic type arguments are mostly removed from the runtime representation, with appropriate casts inserted by the compiler and bridge methods where necessary. Consequently, code generally cannot directly ask for the generic type argument at runtime, and Java cannot use primitive types such as int directly as generic type arguments. C# generics are reified: generic type information remains available at runtime, and the runtime can distinguish constructed generic types. C# also supports generic value types without boxing in many cases.