WordPress WooCommerce ASP.net API WebHookHandler: The WebHook request must contain an entity body formatted as HTML Form Data

Question

I am trying to create a WebHookHandler for Webhooks send from WordPress WooCommerce in ASP.NET C#.

I started with creating a ASP.NET C# Azure API App WebApplication Project and adding the relevant references (Microsoft.AspNet.WebHooks.Common, Microsoft.AspNet.WebHooks.Receivers, Microsoft.AspNet.WebHooks.Receivers.WordPress). Added the WebHookConfig, WordPressWebHookHandler and registered the WebHookConfig in the GlobalAsax.

I then published the application as an Azure App Service.

My WordPressWebHookHandler is still the default of the examples and looks like this:

public class WordPressWebHookHandler : WebHookHandler
{
    public override Task ExecuteAsync(string receiver, WebHookHandlerContext context)
    {
        // make sure we're only processing the intended type of hook
        if("WordPress".Equals(receiver, System.StringComparison.CurrentCultureIgnoreCase))
        {
            // todo: replace this placeholder functionality with your own code
            string action = context.Actions.First();
            JObject incoming = context.GetDataOrDefault<JObject>();
        }

        return Task.FromResult(true);
    }
}

When testing a User Creation WebHook in WooCommerce I can see the request in the log as below.

But unfortunately it is never received while debugging and I see below error.

I am thinking maybe I need a custom WebHook instead of the WordPress specific one as this is a WooCommerce Webhook. Or possibly it is handled wrong in the routing and ends up in another controller.

Any help is much appreciated.

Answer 1

Your WebHookReceiver is wrong

There is a mismatch of expecting HTML Form Data, when in fact it should be expecting JSON.

WordPressWebHookHandler is still the default

This is what is causing your error. If you look at the WordPressWebHookReceiver, the ReceiveAsync() method implementation, calls out to ReadAsFormDataAsync() method, which is not what you want, as your Content-Type is json. So, you want to be doing ReadAsJsonAsync().

Solution: Don't use the WordPressWebHookReceiver and switch it to another one that will call ReadAsJsonAsync().

---

Looking at the code

I am thinking maybe I need a custom WebHook instead of the WordPress specific one as this is a WooCommerce Webhook.

You had the right idea, so I dug up some of the code to explain exactly why this was happening.

The code block below is the ReceiveAsync() method that is overridden in the WordPressWebHookReceiver. You can see that it is calling the ReadAsFormDataAsync() which is not what you want...

public override async Task<HttpResponseMessage> ReceiveAsync(
    string id, HttpRequestContext context, HttpRequestMessage request)
{
    ...
    if (request.Method == HttpMethod.Post)
    {
        // here is what you don't want to be called
        // you want ReadAsJsonAsync(), In short, USE A DIFFERENT RECEIVER.
        NameValueCollection data = await ReadAsFormDataAsync(request);
        ...
    }
    else
    {
       return CreateBadMethodResponse(request);
    }
}

A quick search through the repository for classes that call the ReadAsJsonAsync() method, shows that the following recievers implement it:

1. DynamicsCrmWebHookReceiver
2. ZendeskWebHookReceiver
3. AzureAlertWebHookReceiver
4. KuduWebHookReceiver
5. MyGetWebHookReceiver
6. VstsWebHookReceiver
7. BitbucketWebHookReceiver
8. CustomWebHookReceiver
9. DropboxWebHookReceiver
10. GitHubWebHookReceiver
11. PaypalWebHookReceiver
12. StripeWebHookReceiver
13. PusherWebHookReceiver

I assumed that the CustomWebHookReceiver would fit your requirements, so can grab the NuGet here. Otherwise you can implement your own, or derive it from this class, etc.

---

Configuring a WebHook Recevier

(Copied from the Microsoft Documentation)

Microsoft.AspNet.WebHooks.Receivers.Custom provides support for receiving WebHooks generated by ASP.NET WebHooks

Out of the box you can find support for Dropbox, GitHub, MailChimp, PayPal, Pusher, Salesforce, Slack, Stripe, Trello, and WordPress but it is possible to support any number of other providers

Initializing a WebHook Receiver

WebHook Receivers are initialized by registering them, typically in the WebApiConfig static class, for example:

public static class WebApiConfig
{
    public static void Register(HttpConfiguration config)
    {
        ...

        // Load receivers
        config.InitializeReceiveGitHubWebHooks();
    }
}

Answer 2

There is a problem with the data format that you send in your request. You must use format of HTML Form as your error message said.

Proper POST data format is described here: How are parameters sent in an HTTP POST request?

Don't forget to set Content-Length header and correct Content-Type if your library doesn't do it. Usually the content type is application/x-www-form-urlencoded.