Update examples for subscription validation

For Azure Functions of http trigger type, the event subscription is validated using "options" and by sending the validation code via headers of the response object

Author: grandhiramesh

articles/event-grid/cloudevents-schema.md

@@ -153,35 +153,27 @@ The following sample C# code for an HTTP trigger simulates Event Grid trigger be
 
 ```csharp
 [FunctionName("HttpTrigger")]
-public static async Task<HttpResponseMessage> Run([HttpTrigger(AuthorizationLevel.Anonymous, "get", "post", Route = null)]HttpRequestMessage req, ILogger log)
+public static async Task<HttpResponseMessage> Run([HttpTrigger(AuthorizationLevel.Anonymous, "get", "post", "options", Route = null)]HttpRequestMessage req, ILogger log)
 {
     log.LogInformation("C# HTTP trigger function processed a request.");
+    if (req.Method == "OPTIONS")
+    {
+        // If the request is for subscription validation, send back the validation code
+        
+        var response = req.CreateResponse(HttpStatusCode.OK);
+        response.Add("Webhook-Allowed-Origin", "eventgrid.azure.net");
+
+        return response;
+    }
 
     var requestmessage = await req.Content.ReadAsStringAsync();
     var message = JToken.Parse(requestmessage);
 
-    if (message.Type == JTokenType.Array)
-    {
-        // If the request is for subscription validation, send back the validation code.
-        if (string.Equals((string)message[0]["eventType"],
-        "Microsoft.EventGrid.SubscriptionValidationEvent",
-        System.StringComparison.OrdinalIgnoreCase))
-        {
-            log.LogInformation("Validate request received");
-            return req.CreateResponse<object>(new
-            {
-                validationResponse = message[0]["data"]["validationCode"]
-            });
-        }
-    }
-    else
-    {
-        // The request is not for subscription validation, so it's for an event.
-        // CloudEvents schema delivers one event at a time.
-        log.LogInformation($"Source: {message["source"]}");
-        log.LogInformation($"Time: {message["eventTime"]}");
-        log.LogInformation($"Event data: {message["data"].ToString()}");
-    }
+    // The request is not for subscription validation, so it's for an event.
+    // CloudEvents schema delivers one event at a time.
+    log.LogInformation($"Source: {message["source"]}");
+    log.LogInformation($"Time: {message["eventTime"]}");
+    log.LogInformation($"Event data: {message["data"].ToString()}");
 
     return req.CreateResponse(HttpStatusCode.OK);
 }
@@ -192,22 +184,26 @@ The following sample JavaScript code for an HTTP trigger simulates Event Grid tr
 ```javascript
 module.exports = function (context, req) {
     context.log('JavaScript HTTP trigger function processed a request.');
-
-    var message = req.body;
-    // If the request is for subscription validation, send back the validation code.
-    if (message.length > 0 && message[0].eventType == "Microsoft.EventGrid.SubscriptionValidationEvent") {
+    
+    if (req.method == "OPTIONS) {
+        // If the request is for subscription validation, send back the validation code
+        
         context.log('Validate request received');
-        var code = message[0].data.validationCode;
         context.res = { status: 200, body: { "ValidationResponse": code } };
+        context.res.headers.append('Webhook-Allowed-Origin', 'eventgrid.azure.net');
     }
-    else {
+    else
+    {
+        var message = req.body;
+        
         // The request is not for subscription validation, so it's for an event.
         // CloudEvents schema delivers one event at a time.
         var event = JSON.parse(message);
         context.log('Source: ' + event.source);
         context.log('Time: ' + event.eventTime);
         context.log('Data: ' + JSON.stringify(event.data));
     }
+ 
     context.done();
 };
 ```