Discussion on: Graph Change Notification Web Hook with Azure Functions

[Wilson Ricardo Olarte Martinez]

this code work for me.
using System;
using System.IO;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Azure.WebJobs;
using Microsoft.Azure.WebJobs.Extensions.Http;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Logging;
using Newtonsoft.Json;
using Microsoft.Graph;
using System.Collections.Generic;
using System.Linq;

namespace GraphNotificationHook
{
public class GraphNotification
{
public List value { get; set; }
}

public static class Function1
{
    [FunctionName("GraphNotificationHook")]
    public static async Task<IActionResult> Run(
[HttpTrigger(AuthorizationLevel.Anonymous, "get", "post", Route = null)] HttpRequest req,
    ILogger log)
    {
        log.LogInformation("C# HTTP trigger function processed a request.");

        // parse query parameter
        var validationToken = req.Query["validationToken"];
        log.LogInformation(validationToken);
        if (!string.IsNullOrEmpty(validationToken))
        {
            log.LogInformation("validationToken: " + validationToken);
            return new ContentResult { Content = validationToken, ContentType = "text/plain" };
        }

        string requestBody = await new StreamReader(req.Body).ReadToEndAsync();
        var data = JsonConvert.DeserializeObject<GraphNotification>(requestBody);

        if (!data.value.FirstOrDefault().ClientState.Equals("<YourClientStateValue>", StringComparison.OrdinalIgnoreCase))
        {
            //client state is not valid (doesn't much the one submitted with the subscription)
            return new BadRequestResult();
        }
        //do something with the notification data

        return new OkResult();
    }

}

}