即使使用Task，也无法等待'Void'
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我有个问题。我试图修改我前一段时间制作的应用程序，它仍在WP Phone上工作，但现在我尝试运行它得到这些错误：
在等待我得到：
不能等待'无效'。
当我将void更改为任务时，错误仍然存在
无法等待'无效'
我甚至没有void了。
有人能帮助我吗？
namespace StreamUploadDownload
{
using System.Threading;
public partial class Page1 : PhoneApplicationPage
{
private PhotoCamera _cam;
private double _canvasWidth;
private double _canvasHeight;
private MediaLibrary _library = new MediaLibrary();
public int count = 100;
private static readonly string[] scopes = new string[] { "wl.signin", "wl.basic", "wl.offline_access", "wl.skydrive_update", "wl.skydrive" };
string comboValue;
private LiveConnectClient liveClient;
public int x = 0;
public int y = 0;
public string FileText { get; set; }
public int ComboNumber { get; set; }
public int ConnectionOK { get; set; }
public Page1()
{
InitializeComponent();
}
private void OnSessionChanged(object sender, LiveConnectSessionChangedEventArgs e)
{
this.liveClient = (e.Status == LiveConnectSessionStatus.Connected) ? new LiveConnectClient(e.Session) : null;
if (e.Status == LiveConnectSessionStatus.Connected)
{
btnSignin.Visibility = Visibility.Collapsed;
Pildista.Visibility = Visibility.Visible;
//Pildista2K.Visibility = Visibility.Visible;
Pildista.Content = "Pildista";
}
else
{
Pildista.Visibility = Visibility.Collapsed;
//Pildista2K.Visibility = Visibility.Collapsed;
btnSignin.Visibility = Visibility.Visible;
}
}
protected override void OnNavigatedTo(System.Windows.Navigation.NavigationEventArgs e)
{
if ((PhotoCamera.IsCameraTypeSupported(CameraType.Primary) == true) ||
(PhotoCamera.IsCameraTypeSupported(CameraType.FrontFacing) == true))
{
if (PhotoCamera.IsCameraTypeSupported(CameraType.Primary))
{
_cam = new Microsoft.Devices.PhotoCamera(CameraType.Primary);
_cam.Initialized += new EventHandler<CameraOperationCompletedEventArgs>(cam_Initialized);
_cam.CaptureImageAvailable += new EventHandler<ContentReadyEventArgs>(cam_CaptureImageAvailable);
viewfinderBrush.SetSource(_cam);
//CameraButtons.ShutterKeyPressed += OnButtonFullPress;
base.OnNavigatedTo(e);
if (PhoneApplicationService.Current.State.ContainsKey("Text"))
{
txtvalue.Text = (string)PhoneApplicationService.Current.State["Text"];
FileText = txtvalue.Text;
}
if (PhoneApplicationService.Current.State.ContainsKey("index"))
{
ComboNumber = (int)PhoneApplicationService.Current.State["index"];
}
else
{
// The camera is not supported on the device.
this.Dispatcher.BeginInvoke(delegate()
{
// Write message.
});
// Disable UI.
AFButton.IsEnabled = false;
}
}
}
}
private double GetCameraAspectRatio()
{
IEnumerable<Size> resList = _cam.AvailableResolutions;
if (resList.Count<Size>() > 0)
{
Size res = resList.ElementAt<Size>(0);
return res.Width / res.Height;
}
return 1;
}
void cam_Initialized(object sender, Microsoft.Devices.CameraOperationCompletedEventArgs e)
{
if (e.Succeeded)
{
this.Dispatcher.BeginInvoke(delegate()
{
_canvasHeight = Application.Current.Host.Content.ActualWidth;
_canvasWidth = _canvasHeight * GetCameraAspectRatio();
viewfinderCanvas.Width = _canvasWidth;
viewfinderCanvas.Height = _canvasHeight;
});
}
}
//Failinime andmine ning salvestamine.
private async void cam_CaptureImageAvailable(object sender, Microsoft.Devices.ContentReadyEventArgs e)
{
if (ComboNumber == 1)
{
comboValue = "O";
}
if (ComboNumber == 2)
{
comboValue = "T";
}
if (ComboNumber == 3)
{
comboValue = "S";
}
if (ComboNumber == 4)
{
comboValue = "P";
}
if (ComboNumber == 5)
{
comboValue = "A";
}
if (ComboNumber == 6)
{
comboValue = "M";
}
string fileName = String.Format(FileText + "_" + comboValue + "_" + DateTime.Now.ToString("dd-MM-yyyy_HH-mm-ss") + ".jpg");
try
{
LiveOperationResult operationResult = await this.liveClient.UploadAsync("/me/skydrive", fileName, e.ImageStream, OverwriteOption.Overwrite); //Cannot await 'void'
}
catch (LiveConnectException ex)
{
// e.ImageStream.Close();
// this.infoTextBlock.Text = "Error getting contact info: ";
// this.infoTextBlock.Visibility = Visibility.Visible;
}
finally
{
e.ImageStream.Close();
y++;
Dispatcher.BeginInvoke(delegate()
{
string b = Convert.ToString(y);
loobvalue2.Text = b;
});
}
}
//kaameranupu vajutus.
private void takephoto_Click(object sender, RoutedEventArgs e)
{
if (_cam != null)
{
_cam.CaptureImage();
x++;
string s = x.ToString();
loobvalue.Text = s;
}
}
// Ühenduse Loomine. Session load.
private async void connectButton_Click(object sender, RoutedEventArgs e)
{
bool connected = false;
try
{
var authClient = new LiveAuthClient("RemovedforWeb");
LiveLoginResult result = await authClient.LoginAsync(new string[] { "wl.signin", "wl.skydrive" }); // cannot await 'void'
if (result.Status == LiveConnectSessionStatus.Connected)
{
connected = true;
var connectClient = new LiveConnectClient(result.Session);
var meResult = await connectClient.GetAsync("me");
dynamic meData = meResult.Result; //cannot await 'void'
}
else
{
//btnSignin.Visibility = Visibility.Visible;
}
}
catch (LiveAuthException ex)
{
}
编辑：我添加了更多的代码，并评论有问题的地方
答案
public async Task Method1 ()
{
}
public async Task<int> Method2 ()
{
}
对于上面的代码，“Method1”不返回任何值，而“Method2”返回“int”值。
int i = await Method2(); //this is correct
await Method2(); //this is correct
int i = await Method1(); //this is NOT correct
await Method1(); //this is also correct
对于以下代码行
LiveOperationResult operationResult = await this.liveClient.UploadAsync("/me/skydrive", fileName, e.ImageStream, OverwriteOption.Overwrite); //Cannot await 'void'
“UploadAsync”方法不会返回任何值，如果您说“无法等待'无效'，那就是它的样子”
尝试从代码行中删除“LiveOperationResult operationResult =”并写入 -
await this.liveClient.UploadAsync("/me/skydrive", fileName, e.ImageStream, OverwriteOption.Overwrite);
第二行代码相同 -
LiveLoginResult result = await authClient.LoginAsync(new string[] { "wl.signin", "wl.skydrive" }); // cannot await 'void'
重写为 -
await authClient.LoginAsync(new string[] { "wl.signin", "wl.skydrive" }); // cannot await 'void'
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