C# Assembly Loading and Late Binding

Question

I'm reading this book on C# and .NET and I'm learning a bunch of cool stuff. I've read the part where the author talks about dynamically loading an assembly and creating an instance of a type in that assembly.

In AS3, it's possible to do the same kind of stuff, except for one thing : you can ask the compiler to not compile a set of class, but to check for type safety. Here's an example :

//Defined in an external library
public class A {...}


//In my application, I tell the compiler to type check A, but not compile it
var a:A = new A();
a.whatever();

At runtime in my application code, I can dynamically load my external library containing the definition of class A, load those definitions into my application's ApplicationDomain and everything will run fine. No needs of reflection!

Is this possible in C#?

In other words, can I instruct the C# compiler to typecheck against a bunch of class (let's say, in a library) but exclude them from compilation?

Answer 1

I'm not 100% clear on what the as3 code is doing - but it sounds like you want to define a common interface (in a separate dll) that your external assembly can implement - and simply cast it when you create the object:

Type type = loadedAssembly.GetType(fullyQualifiedName);
IMyInterface obj = (IMyInterface)Activator.CreateInstance(type):

now you can use methods defined on obj easily.

Alternatively, in C# 4.0 the dynamic keyword provides duck-typing.

Answer 2

I just read this

Action Script is a dynamic language, it offers as a "special bonus" a type check feature, it helps you catch bugs at compile time, just like static typed languages do.

C# is a static-typed language, it does all it's type checking at compile time. The type check is not an "added bonus" its an integral feature. C# has always had the ability to late-bind using reflection and the feature is getting better with the new upcoming dynamic keyword.

However, if you use any of the late-binding features that C# has, you get no type checking.