How can I listen in real-time for webhooks in asp.net webforms?

Question

I'm trying to capture the webhooks from the site https://www.unbounce.com in my asp.net web forms application.

I've created HttpAsyncHandler in WebHookHandler.cs

public class WebHookHandler:IHttpAsyncHandler
{
    public WebHookHandler()
    {
    //
    // TODO: Add constructor logic here
    //
    }
    public bool IsReusable { get { return false; } }
    public IAsyncResult BeginProcessRequest(HttpContext context, AsyncCallback cb, object extraData)
    {
        context.Response.Write("<p>Begin IsThreadPoolThread is " + Thread.CurrentThread.IsThreadPoolThread + "</p>\r\n");
        AsynchOperation asynch = new AsynchOperation(cb, context, extraData);
        asynch.StartAsyncWork();
        return asynch;
    }

    public void EndProcessRequest(IAsyncResult result)
    {
    }

    public void ProcessRequest(HttpContext context)
    {
        throw new InvalidOperationException();
    }
}
class AsynchOperation : IAsyncResult
{
    private bool _completed;
    private object _state;
    private AsyncCallback _callback;
    private HttpContext _context;

    bool IAsyncResult.IsCompleted { get { return _completed; } }
    WaitHandle IAsyncResult.AsyncWaitHandle { get { return null; } }
    object IAsyncResult.AsyncState { get { return _state; } }
    bool IAsyncResult.CompletedSynchronously { get { return false; } }

    public AsynchOperation(AsyncCallback callback, HttpContext context, object state)
    {
        _callback = callback;
        _context = context;
        _state = state;
        _completed = false;
    }

    public void StartAsyncWork()
    {
        ThreadPool.QueueUserWorkItem(new WaitCallback(StartAsyncTask), null);
    }

    private void StartAsyncTask(object workItemState)
    {
        _context.Response.Write("<p>Completion IsThreadPoolThread is " + Thread.CurrentThread.IsThreadPoolThread + "</p>\r\n");
        _context.Response.Write("Hello World from Async Handler!\r\n");
        using (var reader = new StreamReader(_context.Request.InputStream))
        {    
            string postData = reader.ReadToEnd();
            _context.Response.Write(postData);
        }


        _completed = true;
        _callback(this);
    }
}

and register my handler and add the map in web.config

<add verb="*" path="webhook.handler" name="WebHookAsyncHandler" type="WebHookHandler"/>

This all is actually taken from msdn (no reputation, sorry)

Next, the other site (unbounce.com) POST something like this:

data.json: {"time_submitted":["04:59 PM UTC"],"page_uuid":["3282389-f13a-44b0-9a49-6321b515d43"],"email":["test@test.com"],"page_name":["Test name"],"date_submitted":["2017-07-17"],"name":["tester"],"ip_address":["80.80.80.80"],"page_url":["http://somepage.url"],"variant":["a"]}

everytime the user presses the button. The POST url is: example.com/webhook.handler

But I don't get the posted data. The output is:

Begin IsThreadPoolThread is True
Completion IsThreadPoolThread is True
Hello World from Async Handler! 

I tried also use _context.Request and _context.Request.Form before StreamReader, but they was NULL everytime.

I think, I have some global misunderstading of how these things work. Can you please help me to display the data from the POST request to my site on the page?

Answer 1

Well, it turned out, that everything was ok in my listing. You just need to set up a good testing enviroment to catch these POSTs, or better, to do them yourself.