//异步加载数据开始doInBackground ();//异步加载数据开始endprotected async void doInBackground (){       var result = await Task.Factory.StartNew((Func<string>)onSuccessfulLogin);                if (result=="") {                    await Task.Factory.StartNew (() => {                        RunOnUiThread (delegate() {                            //跳转到主页面                            Intent intent = new Intent();                            intent.SetClass(this, typeof(Main));                            StartActivity(intent);                            Finish ();                        });                    });                }}    protected string  onSuccessfulLogin ()        {            try {                Thread.Sleep (2000);                Hashtable pars = new Hashtable();                pars.Add("UserName",mAccount);                pars.Add("Password", mPassword);                UserInfoDao userinfodao = new UserInfoDao ();                userinfomodel = userinfodao.getWebservice (pars);                //判断登录                if (userinfomodel != null) {                    if (userinfomodel.UserID > 0) {                        //保持登录的状态 bgein                        ISharedPreferences shared = GetSharedPreferences("UserInfo", FileCreationMode.Private);                        string value = http://www.mamicode.com/shared.GetString("UserInfo", "");                        value =userinfomodel.UserID.ToString().Trim()+"|"+userinfomodel.UserName+"|"+userinfomodel.Token ;                        ISharedPreferencesEditor editor = shared.Edit();                        editor.PutString("UserInfo",value);                        editor.Commit();                        //保持登录的状态 end                    }                }                else                {                    return "用户名或密码错误！";                }            } catch (Exception e) {                return e.ToString();            }            return "";        }