await bitmapImage.SetSourceAsync(randomAccessStream); hangs and kills Xaml app.

Question

Related to: strange-fileloadexceptions.html ( I edited the linked post because this turned out to be unrelated, just an issue with my usage)

When I call SetSourceAsync on a BitmapImage, it never completes and the Xaml app hangs.

Here's a capture of the random access stream feeding into the call. It looks valid.

Answer 1

Hi,
your problem is the use of Task<T> and return type. Try following demo.

XAML

<Page
    x:Class="App1.Page04"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:App04"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d"
    Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
  <Page.DataContext>
    <local:ViewModel/>
  </Page.DataContext>
  <Grid>
    <Image Source="{Binding Picture}"/>
  </Grid>
</Page>

And ViewModel:

using System;
using System.ComponentModel;
using System.Runtime.CompilerServices;
using System.Threading.Tasks;
using Windows.ApplicationModel;
using Windows.Storage;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Media;
using Windows.UI.Xaml.Media.Imaging;

namespace App04
{
  public class ViewModel : INotifyPropertyChanged
  {
    public ViewModel() => GetPicture();

    public ImageSource Picture { get; set; }
    private async void GetPicture()
    {
      string filePath = "Assets\\DwarfPortrait.png";
      StorageFile file = await Package.Current.InstalledLocation.GetFileAsync(filePath);
      Picture = await GetImageSourceFromStorageFile(file);
      OnPropertyChanged(nameof(Picture));
    }

    private static async Task<ImageSource> GetImageSourceFromStorageFile(StorageFile sf)
    {
      using (var randomAccessStream = await sf.OpenAsync(FileAccessMode.Read))
      {
        var result = new BitmapImage();
        await result.SetSourceAsync(randomAccessStream);
        return result;
      }
    }

    public event PropertyChangedEventHandler PropertyChanged;
    internal void OnPropertyChanged([CallerMemberName] string propName = "") =>
      PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propName));
  }
}