无法隐式转换类型IAsyncOperation< StorageFile>.到StorageFile

问题描述

我的代码到底怎么了?

 私有无效的BrowseButton_Click(对象发送者，RoutedEventArgs e){FileOpenPicker FilePicker =新的FileOpenPicker();FilePicker.FileTypeFilter.Add(.exe");FilePicker.ViewMode = PickerViewMode.List;FilePicker.SuggestedStartLocation = PickerLocationId.Desktop;//如果我在这里等我又遇到其他错误¹StorageFile文件= FilePicker.PickSingleFileAsync();如果(文件！= null){AppPath.Text = file.Name;}别的{AppPath.Text =";}} 

它给了我这个错误:

如果我添加"await"(如在代码中注释)，则会出现以下错误:

代码源此处

解决方案

好吧，编译器错误消息非常直接地解释了代码未编译的原因. FileOpenPicker.PickSingleFileAsync 返回 IAsyncOperation< StorageFile> -因此，不能，您不能将该返回值分配给 StorageFile 变量.在C#中使用 IAsyncOperation<> 的典型方法是使用 await .

您只能在 async 方法中使用 await ...因此，您可能希望将方法更改为异步方法:

 私有异步void BrowseButton_Click(对象发送者，RoutedEventArgs e){...StorageFile文件=等待FilePicker.PickSingleFileAsync();...} 

请注意，对于事件处理程序以外的其他任何东西，最好使异步方法返回 Task 而不是 void -使用 void 实际上只是这样，因此您可以使用异步方法作为事件处理程序.

如果您还不太熟悉 async / await ，则应该在继续操作之前先阅读一下- MSDN使用异步和等待进行异步编程" 页可能是一个不错的起点.>

What the hell is wrong with my code?

    private void BrowseButton_Click(object sender, RoutedEventArgs e)
    {
        FileOpenPicker FilePicker = new FileOpenPicker();
        FilePicker.FileTypeFilter.Add(".exe");
        FilePicker.ViewMode = PickerViewMode.List;
        FilePicker.SuggestedStartLocation = PickerLocationId.Desktop;
        // IF I PUT AWAIT HERE   V     I GET ANOTHER ERROR¹
        StorageFile file = FilePicker.PickSingleFileAsync();
        if (file != null)
        {
            AppPath.Text = file.Name;
        }
        else
        {
            AppPath.Text = "";
        }
    }

It gives me this error:

And if I add the 'await', like commented on the code, I get the following error:

Code source here

解决方案

Well, the reason your code doesn't compile is explained pretty directly by the compiler error message. FileOpenPicker.PickSingleFileAsync returns an IAsyncOperation<StorageFile> - so no, you can't assign that return value to a StorageFile variable. The typical way of using IAsyncOperation<> in C# is with await.

You can only use await in async methods... so you probably want to change your method to be asynchronous:

private async void BrowseButton_Click(object sender, RoutedEventArgs e)
{
    ...
    StorageFile file = await FilePicker.PickSingleFileAsync();
    ...
}

Note that for anything other than event handlers, it's better to make an async method return Task rather than void - the ability to use void is really only so you can use an async method as an event handler.

If you're not really familiar with async/await yet, you should probably read up on it before you go any further - the MSDN "Asynchronous Programming with async and await" page is probably a decent starting point.

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