我在异步等待方面相当落后，所以这可能是一个“duh”问题。
我正在开发一个非常简单的 UI 应用程序，它使用 WPF NotifyIcon 库从系统托盘运行。
应用程序应该以以下方式非常简单地运行（对于用户而言）：
我遇到的问题是“异步执行开始”部分。在此之前发生的所有事情都运行良好，但是当程序开始尝试“运行”时，UI 会锁定（我的意思是，用户可以像疯子一样单击托盘图标，并且上下文菜单拒绝出现）。
这种锁定发生的时间过长，令人无法接受。
这是启动代码：
private async void AppStartup( object sender, StartupEventArgs e ) {
this.TRSIcon = this.FindResource( "TRSIcon" ) as TaskbarIcon;
if ( Settings.Default.DoUpgrade ) { //Upgrade if necessary.
Settings.Default.Upgrade( );
Settings.Default.DoUpgrade = false;
Settings.Default.Save( );
}
if ( string.IsNullOrEmpty( Settings.Default.Username ) || string.IsNullOrEmpty( Settings.Default.Password ) ) {
new Help( ).ShowDialog( );
Tuple<string, string> UP;
if ( ( UP = Login.Instance.GetUserPassword( ) ) != null ) {
Settings.Default.Username = UP.Item1;
Settings.Default.Password = UP.Item2;
Settings.Default.Save( );
} else
return;
}
await this.Start( ); //<-----This is where the meat of the program runs and it hangs the UI until it finishes.
return; //<-----This is just so that I have a break point to see that await this.Start is blocking (I have to do it like that right? or do I?)
}
这是
Resources.xaml<ResourceDictionary
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:Tools="clr-namespace:WPFTools.TaskbarNotification;assembly=WPFTools"
xmlns:TR="clr-namespace:TriviaRetriever">
<ContextMenu x:Key="TSRInterfaceMenu" x:Shared="false">
<MenuItem Header="Login" Command="{Binding cmdLogin}"/>
<MenuItem Header="Get My Trivia" Command="{Binding cmdDownload}"/>
<MenuItem Header="Register" Command="{Binding cmdRegister}"/>
<MenuItem Header="Lost Password" Command="{Binding cmdLostPassword}"/>
<MenuItem Header="About" Command="{Binding cmdAbout}"/>
<MenuItem Header="Log Out" Command="{Binding cmdLogout}"/>
<MenuItem Header="Exit" Command="{Binding cmdExit}"/>
</ContextMenu>
<Tools:TaskbarIcon
x:Key="TRSIcon"
MenuActivation="LeftOrDoubleClick"
IconSource="/TRIcon.ico"
DoubleClickCommand="{Binding cmdAbout}"
ContextMenu="{StaticResource TSRInterfaceMenu}">
<Tools:TaskbarIcon.DataContext>
<TR:TRSIViewModel/>
</Tools:TaskbarIcon.DataContext>
</Tools:TaskbarIcon>
</ResourceDictionary>
这是上下文菜单命令的 MVVM：
public class TRSIViewModel {
public ICommand cmdLogin {
get {
return new DelegateCommand {
fncCanExecute = ( ) => ( Application.Current as App ).Core == null,
actCommand = async ( ) => {
Tuple<string, string> LoginPassword = Login.Instance.GetUserPassword( );
if ( LoginPassword != null ) {
Settings.Default.Username = LoginPassword.Item1;
Settings.Default.Password = LoginPassword.Item2;
Settings.Default.Save( );
await ( Application.Current as App ).Start( );
}
}
};
}
}
public ICommand cmdLogout {
get {
return new DelegateCommand {
fncCanExecute = ( ) => ( Application.Current as App ).Core != null,
actCommand = ( ) => {
( Application.Current as App ).Core.Terminate( );
( Application.Current as App ).Core = null;
}
};
}
}
public ICommand cmdRegister {
get {
return new DelegateCommand {
fncCanExecute = ( ) => true,
actCommand = ( ) => Process.Start( @"https://www.digigames.com/weekly_subscriptions/index.php" )
};
}
}
public ICommand cmdLostPassword {
get {
return new DelegateCommand {
fncCanExecute = ( ) => true,
actCommand = ( ) => Process.Start( @"https://www.digigames.com/weekly_subscriptions/lost_password.php" )
};
}
}
public ICommand cmdAbout {
get {
return new DelegateCommand {
fncCanExecute = ( ) => true,
actCommand = ( ) => ( Application.Current as App ).TRSIcon.ShowCustomBalloon( new About( ), PopupAnimation.Slide, 5000 )
};
}
}
public ICommand cmdExit {
get {
return new DelegateCommand {
fncCanExecute = ( ) => true,
actCommand = ( ) => {
if ( ( Application.Current as App ).Core != null )
( Application.Current as App ).Core.Terminate( );
Application.Current.Shutdown( 0 );
}
};
}
}
public ICommand cmdDownload {
get {
return new DelegateCommand {
fncCanExecute = ( ) => ( Application.Current as App ).Core != null,
actCommand = async ( ) => await ( Application.Current as App ).Core.DownloadTrivia( true )
};
}
}
public class DelegateCommand : ICommand {
public Action actCommand { get; set; }
public Func<bool> fncCanExecute { get; set; }
public bool CanExecute( object parameter ) {
return this.fncCanExecute != null && this.fncCanExecute( );
}
public event EventHandler CanExecuteChanged {
add { CommandManager.RequerySuggested += value; }
remove { CommandManager.RequerySuggested -= value; }
}
public void Execute( object parameter ) { this.actCommand( ); }
}
}
我在这里做错了什么？
我认为你的问题完全在于你的
Start但首先要注意的事情。您的断点没有执行您期望的操作。一旦
StartStart了解方法实际释放执行需要多长时间的一个好方法是等待它返回
Taskvar pendingTask = this.Start();
Debugger.Break();
await pendingTask;
Task
方法命中内部异步执行的函数，
Start对象就会返回。一旦
await实际完成，
pendingTask就会返回。在你的情况下，我认为时间会相似，因为
Start
方法没有向后台发送足够的工作。有几种方法可以解决这个问题。如果您的
Start
方法没有与 UI 交互，那就没问题。您只需将整个方法发送到后台即可完成。这工作起来很简单：
await Task.Run(() => this.Start());
这会将任务发送到 ThreadPool 的线程中，并立即再次释放 UI。
Task.Run
方法具有重载，可自动解开
Task方法返回的内部
Start。如果您的方法与 UI 交互，则必须在内部更改该方法。查找方法内耗时较长且不与 UI 交互的部分，并将它们包装到
Task.Run
方法的调用中，如上所示。每个
await
都会再次建立之前存在的
SynchronizationContext。因此，线程中能够更改 UI 的每个
await将确保延续也在同一个线程中执行。所以像这样的事情可以毫无问题地工作：
someLabel.Label = "Working…";
await Task.Run(() => DoManyThings());
someLabel.Label = "Done! :D"
我希望有帮助。如果不知道您的
Start
方法的作用，我无法给您更多提示。但我希望这个答案能让您走上正轨。
我通常的免责声明：我通常使用 VB.net，因此我的 C# 代码可能在语法方面存在缺陷。如果您发现任何错误，请随时编辑它或告诉我出了什么问题。
Thread
并运行它即可。
private void App_OnStartup(object sender, StartupEventArgs e)
{
//Some login logic
if(loggedIn) //Or however you do it
{
Thread thread = new Thread(() =>
{
this.RunWhateverMethodWillDoABunchOfStuff()
});
thread.SetApartmentState(ApartmentState.STA);
thread.Start();
}
根据具体的程序和您想要的内容，您还可以使用
BackgroundWorker
，这是一种很好的异步方式来运行后台操作，同时从后台线程接收进度更新，允许您更新诸如加载栏之类的内容像那样。如果您想了解更多信息，请告诉我编辑：抱歉，我没有注意到您正在运行异步方法。我会避免所有这些，只需以正常方法和线程运行它（假设您不需要进度更新或完成时发出警报，否则使用后台工作程序）。我觉得你把这件事搞得太复杂了。编辑我的代码以反映这一点
编辑 2：这是一个
BackgroundWorker
方法的示例，供任何关心的人使用
BackgroundWorker bw = new BackgroundWorker();
bw.DoWork += BwOnDoWork;
bw.ProgressChanged += BwOnProgressChanged;
bw.RunWorkerCompleted += BwOnRunWorkerCompleted;
bw.WorkerSupportsCancellation = true;
bw.WorkerReportsProgress = true;
//This line here is what starts the asynchronous work
bw.RunWorkerAsync();
private void BwOnRunWorkerCompleted(object sender, RunWorkerCompletedEventArgs runWorkerCompletedEventArgs)
{
//Do whatever you want to do when it is done with its asynchronous task
//for example
Label.Content = "Yay, Were done doing whatever it was that we were doing!!!!"
}
private void BwOnProgressChanged(object sender, ProgressChangedEventArgs e)
{
//Here is where we can send progress reports to the UI, like updating a loading bar
MyProgressBar.EditValue = e.ProgressPercentage;
}
private void BwOnDoWork(object sender, DoWorkEventArgs doWorkEventArgs)
{
//This is where we will put anything we want to be ran asynchronously
this.RunWhateverMethodWillDoABunchOfStuff()
}