Threading noob here.

I'm trying to make a program that pulls a user's profile data from the osu! website, and while doing so the application freezes. You can't drag around the window or anything. I've tried making a task that returns the result after awaiting but it still freezes

private async Task<OsuUserBest[]> GetUserScores()
{

    return await Task.FromResult(osu.GetUserBest(userIdText.Text, 0, 100));
}

private async void OnGoClick(object sender, RoutedEventArgs e)
{
    try
    {
        userScores = await GetUserScores();
        //...

and I've also tried doing Task.Run( () => {code}) but it tells me that a different thread owns it. and I can't await osu.GetUserBest(userIdText.Text, 0, 100) directly because it doesn't contain a definition for GetAwaiter.

Again I'm extremely new to threads and asynchronous tasks, so please excuse my idiocy =)

If you want me to provide anything else to help out feel free to ask.

GitHub repository

CodePudding user response：

You can't access UI elements (or any DispatcherObject in general) from a thread other than the UI thread (dispatcher thread). Either use the Dispatcher.InvokeAsync to access those objects or access them (to copy their values) before you run the background operation:

private async Task<OsuUserBest[]> GetUserScoresAsync()
{
  // Access the DispatcherObject on the UI thread
  string userId = userIdText.Text;

  return await Task.Run(() => osu.GetUserBest(userId, 0, 100));
}

Wrapping IO operations like web requests into a Task.Run should be an absolute exception. Modern APIs will always expose asynchronous operations.