vs xamarin android 读取

private void Btn_Click(object sender, EventArgs e)
{
    var u = FindViewById<EditText>(Resource.Id.editText1).Text;
    var p = FindViewById<EditText>(Resource.Id.editText2).Text;
    var progressDialog = ProgressDialog.Show(this, "Please wait...", "Checking account info...", true);
    var t=new Thread(new ThreadStart(delegate
    {
        var r = Api.CheckUser(u, p);
        if (r.HasValue)
        {
            RunOnUiThread(() => progressDialog.Hide());
            AppConfig.Config.SetNowUserId(r.Value);
            StartActivity(typeof(MainActivity));
            Finish();
        }
        else
        {
            RunOnUiThread(() => Toast.MakeText(this, "用户名或密码错误", ToastLength.Long).Show());
            RunOnUiThread(() => progressDialog.Hide());
        }

    }));
    t.Start();
}

把loading框显示出来，然后开新线程做事，之后关闭loading框