How to return async HttpClient responses back to WinForm?

Question

So far, I have made synchronous HttpWebRequest calls in WinForms applications. I want to start doing this asynchronously so as not to block the UI thread and not freeze. So I'm trying to switch to HttpClient, but I'm also new to async and tasks and don't quite understand it.

I can run the request and get a response and isolate the data I want (result, reasonPhrase, headers, code), but I don’t know how to return them for display in textBox1. I also need to grab ex.message and return to the form if a timeout occurs or the connection fails.

Each individual example that I see has the values ​​written in Console.WriteLine () where they are available, but I need them to return to the form for display and processing and have a hard time understanding how to do this.

Here is a simple example:

namespace AsyncHttpClientTest
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        private void button1_Click(object sender, EventArgs e)
        {
            textBox1.Text = "calling Test()...\r\n";
            DownloadPageAsync();

            // need to get from DownloadPageAsync here: result, reasonPhrase, headers, code 

            textBox1.AppendText("done Test()\r\n");
        }
        static async void DownloadPageAsync()
        {
            // ... Use HttpClient.
            using (HttpClient client = new HttpClient())
            {
                try
                {
                    using (HttpResponseMessage response = await client.GetAsync(new Uri("http://192.168.2.70/")))
                    {
                        using (HttpContent content = response.Content)
                        {
                            // need these to return to Form for display
                            string result = await content.ReadAsStringAsync();
                            string reasonPhrase = response.ReasonPhrase;
                            HttpResponseHeaders headers = response.Headers;
                            HttpStatusCode code = response.StatusCode;
                        }
                    }
                }
                catch (Exception ex)
                {
                    // need to return ex.message for display.
                }
            }
        }
    }
}

Any helpful hints or tips?

Answer 1

create a model to store the data you want to return

public class DownloadPageAsyncResult {
    public string result { get; set; } 
    public string reasonPhrase { get; set; } 
    public HttpResponseHeaders headers { get; set; }
    public HttpStatusCode code { get; set; }
    public string errorMessage { get; set; }
}

Avoid using methods async void. Convert the method to async Taskand call it in the event handler, where allowed.

private async void button1_Click(object sender, EventArgs e) {
    textBox1.Text = "calling Test()...\r\n";
    var result = await DownloadPageAsync();

    // Access result, reasonPhrase, headers, code here

    textBox1.AppendText("done Test()\r\n");
}

static HttpClient client = new HttpClient();
static async Task<DownloadPageAsyncResult> DownloadPageAsync() {
    var result = new DownloadPageAsyncResult();
    try {
        using (HttpResponseMessage response = await client.GetAsync(new Uri("http://192.168.2.70/"))) {
            using (HttpContent content = response.Content) {
                // need these to return to Form for display
                string resultString = await content.ReadAsStringAsync();
                string reasonPhrase = response.ReasonPhrase;
                HttpResponseHeaders headers = response.Headers;
                HttpStatusCode code = response.StatusCode;                    

                result.result = resultString;
                result.reasonPhrase = reasonPhrase;
                result.headers = headers;
                result.code = code;
            }
        }
    } catch (Exception ex) {
        // need to return ex.message for display.
        result.errorMessage = ex.Message;
    }
    return result;
}

HttpClient also should not be created every time a load is called.

HttpClient WebAPI?