ClassByString.cs

using System;
using System.Reflection;

class Program
{
    static void Main()
    {
    	Type t = Type.GetType("Foo");
    	MethodInfo method 
             = t.GetMethod("Bar", BindingFlags.Static | BindingFlags.Public);

    	method.Invoke(null, null);
    }
}

class Foo
{
    public static void Bar()
    {
    	Console.WriteLine("Bar");
    }
}