HttpClient 等待 postasync 从不返回结果

Question

I am trying to write code to send a post request where I upload some files to be handled in PHP. the PHP code is working correctly (I've tested via browser with a real HTML form)

This is how im calling the method where the freezing occurs:

        private void button2_Click(object sender, EventArgs e)
        {
            var res = UploadFiles(files_to_upload);

            if ( res.Result == true ) 
            {



                files_to_upload.Clear();
            }
        }

The method:

private async Task<bool> UploadFiles(List<UploadingFile_t> files)
        {
            using (HttpClient client = new HttpClient())
            using (MultipartFormDataContent formData = new MultipartFormDataContent())
            {

                for (int i = 0; i < files_to_upload.Count; i++)
                {
                    UploadingFile_t file = files_to_upload[i];
                    formData.Add(new StringContent(Path.GetFileName(file.name)), "filename" + i + 1);
                    formData.Add(file.fileStream, "filedata" + 1 + i);
                }

                HttpResponseMessage response = null;

                try
                {
                    client.BaseAddress = new Uri("http://" + Properties.Settings.Default.host);
                    client.Timeout = TimeSpan.FromSeconds(10);
                    string url = "/" + Properties.Settings.Default.host_panel_dir + "/upload_files.php";
                    response = client.PostAsync(url, formData).Result;
                    response.EnsureSuccessStatusCode();
                    client.Dispose();
                }
                catch (HttpRequestException ex)
                {
                    MessageBox.Show(ex.Message);
                    return false;
                }

                if (response.Content.ToString().Contains("UPLSCC") == false)
                {
                    return true;
                }
                else
                {
                    return false;
                }
            }
        }

The code is freezing at the await client.PostAsync(url, formData); or when i try to access the result (if I dont "await" the call). It never returns any result.

I've read a dozen of posts with the same or identical problems and none of them seem to helped me.

I've tried setting a timeout time at 10 seconds, to see if it returns any errors. The returned error was a System.AggregateException : one or more errors occurred. With the inner exception of TaskCanceledException.

I can post more code if needed

Answer 1

By calling Result you are blocking the main thread, which could result in a deadlock.

Change your handler to async void and use await instead.

private async void button2_Click(object sender, EventArgs e)
{
    var res = await UploadFiles(files_to_upload);

    if ( res == true ) 
    {
        files_to_upload.Clear();
    }
}