How can I efficiently update the UI from an async method?

Question

I\'m using a ProgressBar with binding to show the progress when receiving a file from a remote device.

Answer 1

The problem is I have the file transfer method in a different async method

That doesn't necessarily follow. You shouldn't need to use CoreDispatcher explicitly. Asynchronous methods resume on the UI thread by default.

---

For progress reporting, you should use IProgress<T>. You can use it with a structure to report progress, as such:

public struct ProgressReport
{
  public double Progress { get; set; }
  public double FileSize { get; set; }
}

async Task FileTransferAsync(IProgress<ProgressReport> progress)
{
  ...
  if (progress != null)
  {
    progress.Report(new ProgressReport
    {
      Progress = (double)i,
      FileSize = fileSize
    });
  }
  ...
}

Then you can consume it with an IProgress<T> implementation. Since you need UI throttling, you can use one that I wrote that has built-in throttling:

using (var progress = ObservableProgress<ProgressReport>.CreateForUi(value =>
    {
        ProgressFileReceive = (double)value.Progress / value.FileSize * 100;
    }))
{
    await FileTransferAsync(progress);
}