c dynamically loads the dll file and invokes the method of recommendation

Here's the test code:

Create a new classlibrary with two classes, class1 and class2, each of which has a method that returns a string. The code is as follows:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace mydll
{
  public class Class1
  {
    public Class1()
    {

    }
    public string sayhello()
    {
      return "hello,word!";
    }
  }

  public class Class2
  {
    public Class2()
    {

    }

    public string saybeautiful()
    {
      return "beautiful,very good!";
    }
  }

}

After compiling, an mydll. dll dynamic link library will be generated, and then a new winform project will be created (others can also be used for debugging):

private void button1_Click(object sender, EventArgs e)
    {
      string path = @"D:\123\mydll\mydll\bin\Debug\mydll.dll";


      //Byte[] byte1 = System.IO.File.ReadAllBytes(path);// It is also possible 
      //Assembly assem = Assembly.Load(byte1);

      Assembly assem = Assembly.LoadFile(path);


      //string t_class = "mydll.Class1";// Theoretically, it has been loaded dll File, you can get the class type by adding the class name to the namespace, which should be modified as follows: 

      //string t_class = "mydll.Class1,mydll";// If you want to get a class inside this project, you can "namespace" . Parent class... class name " ; If it is external, you need to add " , Link library name " ;

      // Thank you again thy38 The help. 

      //Type ty = Type.GetType(t_class);// When debugging here, ty=null , 1 I don't understand it. I hope someone can solve my doubts 

      Type[] tys = assem.GetTypes();// I have to get all the type names, and then traverse them and distinguish them by type names 
      foreach (Type ty in tys)//huoquleiming
      {
        if (ty.Name == "Class1")
        {
          ConstructorInfo magicConstructor = ty.GetConstructor(Type.EmptyTypes);// Gets a constructor without arguments 
          object magicClassObject = magicConstructor.Invoke(new object[] { });// Here is to get 1 Something similar to an instance of a class 

          //object magicClassObject = Activator.CreateInstance(t);// Obtaining a parameterless construct instance can also be done by 
          MethodInfo mi = ty.GetMethod("sayhello");
          object aa=mi.Invoke(magicClassObject, null);
          MessageBox.Show(aa.ToString());// Here is the execution class class1 Adj. sayhello Method 
        }
        if (ty.Name == "Class2")
        {
          ConstructorInfo magicConstructor = ty.GetConstructor(Type.EmptyTypes);// Gets a constructor that takes no arguments. If there is a constructor and there is no constructor that takes no arguments, this cannot be the case here 
          object magicClassObject = magicConstructor.Invoke(new object[] { });
          MethodInfo mi = ty.GetMethod("saybeautiful");
          object aa = mi.Invoke(magicClassObject, null);// Method has parameters, you need to set the null Replace with a collection of parameters 
          MessageBox.Show(aa.ToString());
        } 
      }

      //AppDomain pluginDomain = (pluginInstanceContainer[key] as PluginEntity).PluginDomain;
      //if (pluginDomain != null)
      //{
      //  AppDomain.Unload(pluginDomain);
      // } 

    }