CloudEvents validation with Azure Functions

cloudevents-options-functions.cs

public static class TestFuncApi
{
    [FunctionName("TestFuncApi")]
    public static async Task<IActionResult> Run(
        [HttpTrigger(AuthorizationLevel.Anonymous, "post", "options", Route = null)] HttpRequest req,
        ILogger log)
    {
        if (req.Method == "OPTIONS")
        {
            // Retrieve the request origin
            if (!req.Headers.TryGetValue("WebHook-Request-Origin", out var headerValues))
                return new BadRequestObjectResult("Not a valid request");

            // Respond with the origin and rate
            var webhookRequestOrigin = headerValues.FirstOrDefault();
            req.HttpContext.Response.Headers.Add("WebHook-Allowed-Rate", "*");
            req.HttpContext.Response.Headers.Add("WebHook-Allowed-Origin", webhookRequestOrigin);

            return new OkResult();
        }

        // Process event notifications
        // Do something here....

        return new OkObjectResult("OK");

    }
}