C# 处理这两个相互依赖的异步方法的最佳方法是什么?
我使用的是Prism库的最新版本 我的列表页面视图模型-ActivityListPageViewModel.cs下面有类似的内容,它基本上是一个列表,单击/选择后将导航到详细信息页面C# 处理这两个相互依赖的异步方法的最佳方法是什么?,c#,xamarin,xamarin.forms,async-await,prism,C#,Xamarin,Xamarin.forms,Async Await,Prism,我使用的是Prism库的最新版本 我的列表页面视图模型-ActivityListPageViewModel.cs下面有类似的内容,它基本上是一个列表,单击/选择后将导航到详细信息页面 public ActivityModel SelectedItem { get => _selectedActivity; set { SetProperty(ref _selectedActivity, value);
public ActivityModel SelectedItem
{
get => _selectedActivity;
set
{
SetProperty(ref _selectedActivity, value);
if (_selectedActivity != null)
ShowActivityDetails(_selectedActivity);
}
}
async void ShowActivityDetails(ActivityModel selectedActivity)
{
var navigationParams = new NavigationParameters();
navigationParams.Add("activity", selectedActivity);
await _navigationService.NavigateAsync("ActivityDetailPage", navigationParams);
}
在我的详细信息页面视图模型中-ActivityDetailPageViewModel.cs
有没有更好的办法
谢谢最简单的解决方案是将覆盖转换为异步,这样您就可以像平常一样调用异步方法了 优点是将正确的上下文传递给异步方法,如果使用Task.Run卸载,则不会发生这种情况
注意:由于这是一个异步无效,您需要小心处理异常,因为它们不会被观察到,因此最好捕获它们。最简单的解决方案是将覆盖转换为异步,这样您就可以像平常一样调用异步方法 优点是将正确的上下文传递给异步方法,如果使用Task.Run卸载,则不会发生这种情况
注意:由于这是一个异步无效,您需要小心处理异常,因为它们不会被观察到,所以最好捕获它们。任务。运行…等待;没有任何意义,您希望它在后台运行TaskRun还是not Wait?Task.run…Wait;没有任何意义,您希望它在后台运行TaskRun还是not Wait?我在'await'操作符上有此错误,只能在异步方法中使用。考虑将此方法标记为“AsiNC”修饰符,并将其返回类型更改为“任务”@ DCopRepublic公共覆盖AutoC空,以注意MyToMin上的异步关键字,以注意异常,您是指NavigatedToNavigationParameters方法上的public override async void吗?@dcpartners是的,最好放一个try-catch来封装该方法的全部内容。并记录结果,或显示用户ect。我在'wait'运算符上有此错误,只能在异步方法中使用。考虑将此方法标记为“AsiNC”修饰符,并将其返回类型更改为“任务”@ DCopRepublic公共覆盖AutoC空,以注意MyToMin上的异步关键字,以注意异常,您是指NavigatedToNavigationParameters方法上的public override async void吗?@dcpartners是的,最好放一个try-catch来封装该方法的全部内容。并记录结果,或向用户显示ect。
public class ActivityDetailPageViewModel : ViewModelBase, IActiveAware, INavigationAware
{
private readonly IActivityApiService _activityApiService;
private readonly ICategoryApiService _categoryApiService;
private readonly INavigationService _navigationService;
private readonly IPageDialogService _dialogService;
public DelegateCommand DeleteCommand { get; private set; }
public DelegateCommand SaveCommand { get; private set; }
private ActivityModel _activity;
public ActivityModel Activity
{
get { return this._activity; }
set
{
SetProperty(ref this._activity, value);
}
}
private ActivityModelValidator _activityValidator;
private bool _isActive;
public bool IsActive
{
get { return _isActive; }
set
{
_isActive = value;
SetProperty(ref _isActive, value, RaiseIsActiveChange);
}
}
private List<CategoryModel> _categoryList;
public List<CategoryModel> CategoryList
{
get => _categoryList;
set => SetProperty(ref _categoryList, value);
}
private CategoryModel _selectedCategory;
public event EventHandler IsActiveChanged;
public CategoryModel SelectedCategory
{
get => _selectedCategory;
set => SetProperty(ref _selectedCategory, value);
}
//public bool IsActive { get => throw new NotImplementedException(); set => throw new NotImplementedException(); }
public ActivityDetailPageViewModel(CategoryApiService categoryApiService, ActivityApiService activityApiService, INavigationService navigationService, IPageDialogService dialogService) : base(navigationService)
{
_categoryApiService = categoryApiService;
_activityApiService = activityApiService;
_navigationService = navigationService;
_dialogService = dialogService;
_activityValidator = new ActivityModelValidator();
Title = "Activity";
DeleteCommand = new DelegateCommand(DeleteActivity);
SaveCommand = new DelegateCommand(SaveActivity);
}
protected virtual void RaiseIsActiveChange()
{
IsActiveChanged?.Invoke(this, EventArgs.Empty);
}
public override void OnNavigatedTo(INavigationParameters parameters)
{
var activity = parameters["activity"] as ActivityModel;
Activity = activity ?? new ActivityModel();
Task.Run(async () => { await FetchCategories(); }).Wait();
Task.Run(async () => { await FetchActivityDetail(); });
}
public async Task FetchActivityDetail()
{
if (Activity.Id > 0)
{
Activity = await _activityApiService.GetActivity(Activity.Id);
SelectedCategory = CategoryList.FirstOrDefault(x => x.Id == Activity.CategoryId);
}
}
public async Task FetchCategories()
{
CategoryResultModel categoryResult = await _categoryApiService.GetCategories();
CategoryList = categoryResult.Results;
}
async void SaveActivity()
{
Activity.CategoryId = SelectedCategory.Id;
Activity.CategoryName = SelectedCategory.Name;
var validationResults = _activityValidator.Validate(Activity);
if (validationResults.IsValid)
{
if (Activity.Id != 0)
{
bool isUserAccept = await _dialogService.DisplayAlertAsync("Activity", "Update the details", "OK", "Cancel");
if (isUserAccept)
{
var response = await _activityApiService.UpdateActivity(Activity.Id, Activity);
if (!response)
{
await _dialogService.DisplayAlertAsync("Activity", "Error.", "OK");
}
else
{
await _navigationService.NavigateAsync("NavigationPage/ActivityListPage");
}
}
}
else
{
bool isUserAccept = await _dialogService.DisplayAlertAsync("Activity", "Add a new details", "OK", "Cancel");
if (isUserAccept)
{
var response = await _activityApiService.AddActivity(Activity);
if (!response)
{
await _dialogService.DisplayAlertAsync("Activity", "Error.", "OK");
}
else
{
await _navigationService.NavigateAsync("NavigationPage/ActivityListPage");
}
}
}
}
else
{
await _dialogService.DisplayAlertAsync("Activity", validationResults.Errors[0].ErrorMessage, "OK");
}
}
async void DeleteActivity()
{
var alert = await _dialogService.DisplayAlertAsync("Activity", "Do you want to delete this item?", "Yes", "Cancel");
if (alert)
{
var response = await _activityApiService.DeleteActivity(Activity.Id);
if (!response)
{
await _dialogService.DisplayAlertAsync("Activity", "Error.", "OK");
}
else
{
await _navigationService.NavigateAsync("NavigationPage/ActivityListPage");
}
}
}
}
Task.Run(async () => { await FetchCategories(); }).Wait();
Task.Run(async () => { await FetchActivityDetail(); });
Task.Run(async () => { await FetchCategories(); await FetchActivityDetail(); });
public override async void OnNavigatedTo(INavigationParameters parameters)
{
try
{
var activity = parameters["activity"] as ActivityModel;
Activity = activity ?? new ActivityModel();
await FetchCategories();
await FetchActivityDetail();
}
catch(Exception ex)
{
// log or tell the user
}
}