反射小例

    /// <summary>
    /// 接口中首先定义方法名称
    /// </summary>
    public interface IPlugs
    {
        string Name { get; }

        string Process(string str);
    }

    /// <summary>
    /// 实现接口方法
    /// </summary>
    class ToLower:IPlgus.IPlugs
    {
        public string Name
        {
            get { return "大写转小写"; }
        }

        public string Process(string str)
        {
            return str.ToLower();
        }
    }

然后生成DLL文件复制到主程序bin文件夹中

   using System.Reflection;
    /// <summary>
    /// 动态获取dll并且添加到主程序
    /// </summary>
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {

            Type t=typeof(IPlgus.IPlugs);     //获取接口type
            string path = AppDomain.CurrentDomain.BaseDirectory;   //获取程序执行根目录

            path += "IPlugs\";

            string[] strs = System.IO.Directory.GetFiles(path, "*.dll");    //获取对应目录中dll的文件路径

            if(strs.Length>0)
            {
                for (int i = 0; i < strs.Length; i++)
                {
                    Assembly ass = Assembly.LoadFile(strs[i]);     //获取程序集
                    if(ass!=null)
                    {
                        Type[] types = ass.GetTypes();   //获取程序集中的Type
                        if(types.Length>0)
                        {
                            foreach (Type item in types)
                            {
                                if(t.IsAssignableFrom(item))
                                {
                                    ToolStripMenuItem tool = new ToolStripMenuItem();

                                    PropertyInfo pinfo = item.GetProperty("Name");   //获取Type中的属性

                                    object obj = Activator.CreateInstance(item);    //根据获取的Type实例化对象
                                    object value = pinfo.GetValue(obj);           //获取Type属性中的值
                                    tool.Text = value.ToString();
                                  //  tool.Click += tool_Click;
                                    tool.Click += new EventHandler(tool_Click);
                                    tool.Tag = item;
                                    this.功能ToolStripMenuItem.DropDownItems.Add(tool);
                                }
                            }
                        }
                    }
                }
            }
        }

        void tool_Click(object sender, EventArgs e)
        {
            string text = this.textBox1.Text.Trim();
            if(text=="")
            {
                MessageBox.Show("没法转");
            }
            ToolStripMenuItem tool=sender as ToolStripMenuItem;
            Type t=(Type)tool.Tag;
            object model = Activator.CreateInstance(t);
            MethodInfo minfo=t.GetMethod("Process");    //获取Type中的方法
            object newtext = minfo.Invoke(model, new object[] { text });          //执行从Type中获取的方法
            this.textBox1.Text = newtext.ToString();
        }
    }