asp.net中使用cookie与md5加密实现记住密码功能的实现代码

在做一个前台的登陆和后台的信息审核管理功能时，需要用到记住密码的模块：
虽然.net内置了登陆控件，有记住密码的功能，但还是想自己实践一下，以下代码主要应用了COOKIE，包括安全加密的过程等。

代码如下:
//设置，删除Cookie
//provider Vevb.com
        protected void set_cookie()
        {
            HttpCookie UserNameCookie = Request.Cookies["UserNameCookie"];
            HttpCookie UserPasswordCookie = Request.Cookies["UserPasswordCookie"];
            if (this.CheSave.Checked)
            {
                lblcookie.Text = "1";
                //保存用户名和密码到cookie
                if (UserNameCookie == null)
                {
                    UserNameCookie = new HttpCookie("UserNameCookie");
                    UserNameCookie.Values.Add("UserName", TxtUserName.Text);
                    UserNameCookie.Expires = DateTime.Now.AddDays(30);
                    Response.Cookies.Add(UserNameCookie);
                }
                //修改COOKIE
                else if (UserNameCookie.Values["UserName"] != TxtUserName.Text)
                {
                    SetToCookie(UserNameCookie, "UserName", TxtUserName.Text);
                }
                if (UserPasswordCookie == null)
                {
                    UserPasswordCookie = new HttpCookie("UserPasswordCookie");