任务扩展以满足 App 范围的服务呼叫

问：

我正在使用 xamarin 并尝试使用一种方法使用所有服务。为此，我编写了一个 TaskExtension。因此，我可以从应用程序的每个页面调用该扩展方法。这是为了禁用按钮、显示加载屏幕、响应处理，并从一点满足异常处理。我在下面附上我的代码。需要您对此解决方案的专家意见

这是我的扩展类

public static class TaskExtensions
{
    public static async Task<ResultViewModel<U>> ExecuteAsyncOperation<U>(this Task<HttpResponseMessage> operation, object sender = null)
    {
        ResultViewModel<U> resultModel = new ResultViewModel<U>();
        Button button = BeforeAsyncCall(sender);
        try
        {
            await BackgroundOperation(operation, resultModel);
        }
        catch (Exception ex)
        {
            resultModel.Status = HttpStatusCode.InternalServerError;
            resultModel.Errors = new List<string>() { "Some error occurred. Please try again." };
        }
        finally
        {
            AfterAsyncCall(button);

        }
        return resultModel;
    }
    static async Task BackgroundOperation<U>(Task<HttpResponseMessage> operation, ResultViewModel<U> resultModel)
    {
        HttpResponseMessage RawResult = await operation;
        var Response = await RawResult.Content.ReadAsStringAsync();
        resultModel.Status = RawResult.StatusCode;
        if (RawResult.IsSuccessStatusCode)
        {
            var responseObj = await Task.Run(() => JsonConvert.DeserializeObject<U>(Response));
            resultModel.Result = responseObj;
        }
        else
        {
            var responseErrorObj = await Task.Run(() => JsonConvert.DeserializeObject<ErrorModel>(Response));
            resultModel.Errors = new List<string>();
            foreach (var modelState in responseErrorObj.ModelState)
            {
                foreach (var error in modelState.Value)
                {
                    resultModel.Errors.Add(error.ToString());
                }
            }
        }
    }
    static Button BeforeAsyncCall(object sender)
    {
        Button button = null;
        if (sender != null)
            button = (Button)sender;
        if (button != null)
            button.IsEnabled = false;
        UserDialogs.Instance.ShowLoading("Loading", MaskType.Black);
        return button;
    }
    static void AfterAsyncCall(Button button)
    {
        UserDialogs.Instance.HideLoading();
        if (button != null)
            button.IsEnabled = true;
    }
}

这是对我的扩展方法的调用

ResultViewModel<TokenModel> response = await new Service(Settings.BaseUrl).Login(loginModel).ExecuteAsyncOperation<TokenModel>(sender);

结果视图模型

public class ResultViewModel<T> 
    {
        public HttpStatusCode Status { get; set; }
        public T Result { get; set; }
        public List<string> Errors { get; set; }
    }

Async 方法

public async Task<HttpResponseMessage> Login(LoginViewModel loginModel)
        {
            try
            {

                var dataList = new List<KeyValuePair<string, string>>();
                dataList.Add(new KeyValuePair<string, string>("grant_type", "password"));
                dataList.Add(new KeyValuePair<string, string>("username", loginModel.Email));
                dataList.Add(new KeyValuePair<string, string>("password", loginModel.Password));
                var request = new HttpRequestMessage()
                {
                    RequestUri = new Uri(this.BaseUrl + "token"),
                    Method = HttpMethod.Post,
                    Content = new FormUrlEncodedContent(dataList)
                };
                var authenticateResponse = await Client.SendAsync(request);
                return authenticateResponse;
            }
            catch (Exception ex)
            {
                return null;
            }
        }

我的问题是

1）这是一个好方法吗？

2）我们可以在性能方面改进它吗？

3） 我是否正确使用异步？