Interface constraints cannot be retrieved using methods of the System.Reflection.Emit.GenericTypeParameterBuilder class. Once you have created the generic type that contains the type parameter, you can use its Type object to reflect the type parameters and their constraints. To get the type parameters of a completed generic type, use the Type.GetGenericArguments method. For each type parameter, get the base type constraint and interface constraints by using the Type.GetGenericParameterConstraints method.