C# Reflection, changing a method's body

Question

Is it possible to change the body of method during runtime?

class Person
{
    public void DoSth()
    { Console.WriteLine("Hello!"); }
}

I wanted to have a simple input field (like a textbox) where I can write the method body source code during runtime.

The textbox may contain data like:

for (int i = 0; i < 5; i++)
     Console.WriteLine(i);

which should be excecuted when

new Person().DoSth()

is called.

Is (or how is) this possible in C# (using Reflection)?
Thanks for your help in advance.

EDIT:
If the above isn't possible, is it possible to create a new method during runtime and call it?

Answer 1

Reflection.Emit is one way of generating IL at runtime... http://msdn.microsoft.com/en-us/library/8ffc3x75(v=VS.90).aspx

Lightweight code generation is another... http://blogs.msdn.com/b/joelpob/archive/2004/03/31/105282.aspx

However, neither take C# and compile it. For this you'll most likely need to invoked the C# compiler.

What is your use case (why do you want to do this)? There are security considerations with running code within your app domain, so you need to work out how you'd deal with this.