So, let's recap: we had regular connectors, we had poll triggers. So, we're still missing the push triggers. A poll trigger needs to be polled regularly by the logic app to see if it can continue. A push trigger does not have to be polled, it will tell the logic app when it needs to continue, passing the necessary information. At this moment a push trigger needs to be called by a webhook-action. Your trigger needs two function : Subscribe and Unsubscribe. In the Webhook-action these functions will automatically be called when the Logic App starts or stops. The WebHook action needs to pass the callback-url to your Subscribe/Unsubscribe-action. This callback-url is the url your API app will call for starting the Logic App. Your functions should look like this :
public static List subscriptions = new List();
[HttpPost, Route("api/webhooktrigger/subscribe")]
public HttpResponseMessage Subscribe([FromBody] string callbackUrl)
{
subscriptions.Add(callbackUrl);
return Request.CreateResponse();
}
[HttpPost, Route("api/webhooktrigger/unsubscribe")]
public HttpResponseMessage Unsubscribe([FromBody] string callbackUrl)
{
subscriptions.Remove(callbackUrl);
return Request.CreateResponse();
}
The idea is that you call back the logic apps using the list of subscriptions as this:
using (HttpClient client = new HttpClient())
{
foreach (string callbackUrl in subscriptions)
await client.PostAsync(callbackUrl,
@"{""trigger"":""fired""}",
new JsonMediaTypeFormatter(), "application/json");
}
After this your Logic app continues.
For using the pushtrigger you need a webhook-connector in your logic app. This needs to call the subscribe and unsubscribe-methods of your API App. For the body you need to pass the callback url.
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But still it won't work. When going to the Trigger History you can find that you get a failure because of an error with the content-Type. It is simple to solve: Show the advanced options of your webhook-connector and add the content-type to your subscribe- and unsubscribe-headers as this:
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Problem solved !