C# type or namespace expected confusion

Question

Im getting slightly confused by a C# error.

Type t = thing.GetType()

t is now a type. but if i attempt to do this:

new GenericThing<t>

I get a warning saying type or namespace expected. What am i missing?

Answer 1

t is a Type object created at runtime. Generics expect a type name, resolved at compile time. To create a generic at runtime, you have to use MakeGenericType

For example:

Activator.CreateInstance(typeof(GenericThing<>).MakeGenericType(t));

Answer 2

t is an object instance of type Type , ie something that only exists at runtime. Generics work at compile time and expect the name of the type.

I think you agree that the following doesn't make sense:

Type t = thing.GetType()
TypeOfThing instance = new t();

And for the same reason, you can't pass a type instance as the parameter of a generic.

Answer 3

Type是代表一个类型，而不是实际上是一个，所以你不能使用实例的类Type在期望一个类型或类型参数的地方。

Answer 4

you should do something like this :

var youGeneric = typeof(GenericThing<>).MakeGenericType(t)
                                       .GetConstructor(Type.EmptyTypes)
                                       .Invoke(null);