/// <summary>
        /// 压缩文件夹
        /// </summary>
        /// <param name="DirectoryName"></param>
        /// <param name="ZipFileName"></param>
        public static void Zip_Directory(string DirectoryName, string ZipFileName, string SavePath)
        {
            //压缩
            String myRar;
            RegistryKey myReg;
            Object myObj;
            String myInfo;
            ProcessStartInfo myStartInfo;
            Process myProcess;
            try
            {
                myReg = Registry.ClassesRoot.OpenSubKey(@"Applications\WinRAR.exe\Shell\Open\Command");
                myObj = myReg.GetValue("");
                myRar = myObj.ToString();
                myReg.Close();
                myRar = myRar.Substring(1, myRar.Length - 7);
                //rar命令参数
                myInfo = "a  -r  -ep1 " + SavePath + "\\" + ZipFileName + " " + DirectoryName;//a-压缩 -r -ep1文件夹内的全部文件和文件夹加入到压缩文件 压缩文件保存地址 要压缩的目录
                myStartInfo = new ProcessStartInfo();
                myStartInfo.FileName = myRar;
                myStartInfo.Arguments = myInfo;
                myStartInfo.WindowStyle = ProcessWindowStyle.Hidden;
                myStartInfo.WorkingDirectory = DirectoryName;//获取或设置要启动的进程的初始目录。
                myProcess = new Process();
                myProcess.StartInfo = myStartInfo;
                myProcess.Start();
            }
            catch { }
        }

调用WinRar进行压缩

需要引用的命名空间

using Microsoft.Win32;
using System.Runtime.InteropServices;
using System.Diagnostics;

使用开源库 SharpZipLib 吧，不需要 WinRAR 也可以进行压缩、解压缩。

下面是代码示例：

http://www.cnblogs.com/bobofsj11/archive/2008/07/03/1234679.html