c#动态加载dll文件

1.在写一个记录日志到文件中的类库（生成dll文件copy到一个目录中去，然后在主函数的appconfig中去配置。

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace WriteToTxtLib
{
    public class WriteLog
    {
        public void Write(string logMessage)
        {
            using (StreamWriter sw =  new StreamWriter("e:\\test\\writelog.txt",true))
            {
                sw.WriteLine(DateTime.Now.ToLongDateString() + logMessage);
            }
        }
    }
}

2.新建一个测试的主函数，其中appconfig进行如下配置

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <startup>
        <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
    </startup>
  <appSettings>
    <add key="dllNamespaceName" value="WriteToWordLib"/>
    <add key="dllClassName" value="WriteLog"/>
    <add key="dllMethodName" value="Write"/>
    <add key="dllPath" value="e:\test\WriteToWordLib.dll"/>

  </appSettings>
</configuration>

3.给主函数添加如下代码

using System;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.Configuration;
using System.Linq;
using System.Management.Instrumentation;
using System.Reflection;
using System.Text;
using System.Threading.Tasks;
using System.Configuration;
using System.Data;
using System.Drawing;
using System.Text;
using System.IO;
using System.Collections;
using System.Configuration;

namespace 我的日志功能函数
{
    class Program
    {
        static void Main(string[] args)
        {
            WriteLog("主函数开始");
            Console.ReadKey();
        }

        private static void WriteLog(string logMessage)
        {
            /*
             * 这是appconfig文件中的指定的内容
                <add key="dllNamespaceName" value="WriteToTxtLib"/>
                <add key="dllClassName" value="WriteLog"/>
                <add key="dllMethodName" value="Write"/>
                <add key="dllPath" value="e:\\test\WriteToTxtLib.dll"/>
             */
            //获取到命名空间,类名，方法名，dll路径
            string dllNamespaceName = System.Configuration.ConfigurationSettings.AppSettings["dllNamespaceName"].ToString();
            string dllClassName = System.Configuration.ConfigurationSettings.AppSettings["dllClassName"].ToString();
            string dllMethodName = System.Configuration.ConfigurationSettings.AppSettings["dllMethodName"].ToString();
            string dllPath = System.Configuration.ConfigurationSettings.AppSettings["dllPath"].ToString();

            Assembly asm = Assembly.LoadFile(dllPath);//加载dll
            Type classType = asm.GetType(dllNamespaceName + "." + dllClassName);//获取类型
            object obj = Activator.CreateInstance(classType);//根据类型创建对象
            MethodInfo method = classType.GetMethod(dllMethodName);//找到指定的方法
            object o = method.Invoke(obj, new object[] { logMessage });//调用方法
        }
    }
}