Microsoft Graph API - Manage Booking API Authorization has been denied for this request - microsoft-graph-api

Question

I have a simple ASP.Net web application consist of .aspx web from hosted on azure as cloud service. In my application there is no user login.
I want to connect with Microsoft Graph API and and to use Microsoft Bookings API to get the BookingBusiness collection on my home page load without user login. I am currently debugging my web app on my desktop using Azure emulator.
I have the ofiice 365 premium account access assoiciated with my microsoft account (v-sheeal#microsoft.com) and I had created a Booking business using my v- alias through Booking tools (https://outlook.office.com/owa/?path=/bookings).
I registered an app in AAD in the same tenant with all required permission and provided the Cliend Id and secret in the code to get the access token. I am using Client credentials Grant flow to get the access token and try to invoke the booking API. I am able to get the access token, but when the code try to get the the list of booking businesses it is giving below exception.
DataServiceClientException: {
"error": {
"code": "",
"message": "Authorization has been denied for this request.",
"innerError": {
"request-id": "d0ac6470-9aae-4cc2-9bf3-ac83e700fd6a",
"date": "2018-09-03T08:38:29"
}
}
}
The code and registered app setting details are in below screen shot.
.aspx.cs
private static async Task<AuthenticationResult> AcquireToken()
{
var tenant = "microsoft.onmicrosoft.com";
//"yourtenant.onmicrosoft.com";
var resource = "https://graph.microsoft.com/";
var instance = "https://login.microsoftonline.com/";
var clientID = "7389d0b8-1611-4ef9-a01f-eba4c59a6427";
var secret = "mxbPBS10|[#!mangJHQF791";
var authority = $"{instance}{tenant}";
var authContext = new AuthenticationContext(authority);
var credentials = new ClientCredential(clientID, secret);
var authResult = await authContext.AcquireTokenAsync(resource,
credentials);
return authResult;
}
protected void MSBooking()
{
var authenticationContext = new
AuthenticationContext(GraphService.DefaultAadInstance,
TokenCache.DefaultShared);
var authenticationResult = AcquireToken().Result;
var graphService = new GraphService(
GraphService.ServiceRoot,
() => authenticationResult.CreateAuthorizationHeader());
// Get the list of booking businesses that the logged on user can see.
var bookingBusinesses = graphService.BookingBusinesses; ----- this
line throwing an exception "Authorization has been denied for
this request."
}
GraphService.cs
namespace Microsoft.Bookings.Client
{
using System;
using System.Net;
using Microsoft.OData;
using Microsoft.OData.Client;
public partial class GraphService
{
/// <summary>
/// The resource identifier for the Graph API.
/// </summary>
public const string ResourceId = "https://graph.microsoft.com/";
/// <summary>
/// The default AAD instance to use when authenticating.
/// </summary>
public const string DefaultAadInstance =
"https://login.microsoftonline.com/common/";
/// <summary>
/// The default v1 service root
/// </summary>
public static readonly Uri ServiceRoot = new
Uri("https://graph.microsoft.com/beta/");
/// <summary>
/// Initializes a new instance of the <see
cref="BookingsContainer"/> class.
/// </summary>
/// <param name="serviceRoot">The service root.</param>
/// <param name="getAuthenticationHeader">A delegate that returns
the authentication header to use in each request.</param>
public GraphService(Uri serviceRoot, Func<string>
getAuthenticationHeader)
: this(serviceRoot)
{
this.BuildingRequest += (s, e) => e.Headers.Add("Authorization",
getAuthenticationHeader());
}
}

Answer 1

According to your description, I assume you want to use the Microsoft Bookings API.
Base on the images you’ve provided, You are missing define scope in your code and the Authority is incorrectly.
We can review document to get an Access Token without a user.