private object GetInstanceByName(string className)
    {
             object obj;

             try
             {
                    obj = Activator.CreateInstance(Type.GetType(className));
                    MessageBox.Show(obj.GetType().ToString());
             }


            //创建Button实例的过程：Button btn=(Button)GetInstanceByName("System.Windows.Forms");
            //btn.Parent=this;

            //Assembly asm = Assembly.LoadWithPartialName(className);
            //try
            //{
            //    obj = Activator.CreateInstance(asm.GetType(className + ".Button"));
            //    MessageBox.Show(obj.GetType().ToString());
            //}   
         
            catch (Exception e)
            {
                  throw new Exception("动态创建实例失败 \n\n=> " + className, e);
            }
            return obj;
    }

private void button1_Click(object sender, EventArgs e)
    {
            //Int32 myInt=(Int32)GetInstanceByName("System.Int32");
              
            //得到Assembly名字的方法：
            //对于自定义的数据类型，需要通过Assemebly类得到程序集的全名（其实就是反射机制）
               Assembly asm = Assembly.Load("Test");   //加载程序集，Test为程序集的名字
               GetInstanceByName("Application1.Form1, " + asm.FullName);  //Application1.Form1表示命名空间Application1中的一个类"Form1"
                MessageBox.Show(asm.FullName);
    }

Assembly assembly = Assembly.LoadFrom("MyTest.dll");
Type type = assembly.GetType("MyTest.MyClass");
object instance = Activator.CreateInstance(type);