UWP FileOpenPicker 的使用注意点

从Winform迁移到UWP之后发现FileOpenDialog这个好用的控件不见了。查了Bing之后才知道在UWP中是用FileOpenPicker了。

下面这个就是微软的示例代码，但是放到我们UWP的事件函数中会报错 ”await 只能用于异步方法中，请考虑使用async修饰方法”

var picker = new Windows.Storage.Pickers.FileOpenPicker();
picker.ViewMode = Windows.Storage.Pickers.PickerViewMode.Thumbnail;
picker.SuggestedStartLocation = Windows.Storage.Pickers.PickerLocationId.PicturesLibrary;
picker.FileTypeFilter.Add(".jpg");
picker.FileTypeFilter.Add(".jpeg");
picker.FileTypeFilter.Add(".png");

Windows.Storage.StorageFile file = await picker.PickSingleFileAsync();
if (file != null)
{
    // Application now has read/write access to the picked file
    this.textBlock.Text = "Picked photo: " + file.Name;
}
else
{
    this.textBlock.Text = "Operation cancelled.";
}

 报错位置在 “await”所在的行，这种用法我很陌生。捣鼓了半天也没有整通过。

private void PickAFileButton_Click(object sender, RoutedEventArgs e)
        {
            // Clear previous returned file name, if it exists, between iterations of this scenario
            OutputTextBlock.Text = "";

            FileOpenPicker openPicker = new FileOpenPicker();
            openPicker.ViewMode = PickerViewMode.Thumbnail;
            openPicker.SuggestedStartLocation = PickerLocationId.PicturesLibrary;
            openPicker.FileTypeFilter.Add(".jpg");
            openPicker.FileTypeFilter.Add(".jpeg");
            openPicker.FileTypeFilter.Add(".png");
            StorageFile file = await openPicker.PickSingleFileAsync();
            if (file != null)
            {
                // The StorageFile has read/write access to the picked file.
                // See the FileAccess sample for code that uses a StorageFile to read and write.
                OutputTextBlock.Text = "Picked photo: " + file.Name;
            }
            else
            {
                OutputTextBlock.Text = "Operation cancelled.";
            }
        }

后来找到了一份微软的SampleCode，才整明白。其实解决方法很简单，就像报错提示的一样。在事件函数前面加上“async”就可以了。

private async void PickAFileButton_Click(object sender, RoutedEventArgs e){

 在示例代码中，我们看到获取文件名就直接调用 StorageFile.Name， 但是这个文件名是不包含完整路径的，包含完整路径的文件名是 StorageFile.Path.