list<Model>判断用户是否存在，取出model只修改指定值

Dqt.Reporter.BLL.user UserBLL = new Dqt.Reporter.BLL.user();
Dqt.Reporter.Model.user UserModel = new Dqt.Reporter.Model.user();
List<Dqt.Reporter.Model.user> userlist = UserBLL.GetModelList("(UserName='" + txt_user_name.Text.Trim() + "' or Email='" + txt_user_name.Text.Trim() + "')" + " and UserPassword='" + MFunction.Md5HashString(txt_user_pwd.Text.Trim().ToString()) + "'");
if (userlist.Count > 0)
{
UserModel = userlist[0];
UserModel.LastLoginIp = Request.UserHostAddress;
UserModel.LastLoginTime = Util.TimeToUnixTimes(DateTime.Now.ToString());
UserBLL.Update(UserModel);