Azure – Call Microsoft Graph API with Function App that is linked to a Static Web App

As you are using BYOF, The Function code will work separately and the authentication you are doing in Azure Static Web app will not work. And as Azure Functions cannot run interactive login inside the App, You cannot use User specific flows like Implicit flow or Auth code flow wherever User interaction via Browser login is required.

Here, You need to create one Azure Functions with Client Credentials Flow using Azure service principal- Client Id, Client Secret and Tenant Id like below.

Reference here.

My Function1.cs:-

using Azure.Core;
using Azure.Identity;
using Newtonsoft.Json;
using System;
using System.Net.Http;
using System.Threading.Tasks;
using Azure.Core;
using Azure.Identity;
using Newtonsoft.Json;
using System;
using System.Net.Http;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Azure.WebJobs;
using Microsoft.Azure.WebJobs.Extensions.Http;
using Microsoft.Extensions.Logging;
using System.Net.Http.Json;

namespace FunctionApp1
{
    public static class Function1
    {
        [FunctionName("Function1")]
        public static async Task<IActionResult> Run(
            [HttpTrigger(AuthorizationLevel.Function, "get", Route = null)] HttpRequest req,
            ILogger log)
        {
            log.LogInformation("C# HTTP trigger function processed a request.");

            var token = await GetAccessToken("Tenant-Id", "Client-Id", "Client-Secret");
            var results = await GetResults(token);

            return new OkObjectResult(results);
        }

        private static async Task<string> GetAccessToken(string tenantId, string clientId, string clientKey)
        {
            var credentials = new ClientSecretCredential(tenantId, clientId, clientKey);
            var result = await credentials.GetTokenAsync(new TokenRequestContext(new[] { "https://graph.microsoft.com/.default"
}), default);
            return result.Token;
        }

        private static async Task<string> GetResults(string token)
        {
            var httpClient = new HttpClient
            {
                BaseAddress = new Uri("https://graph.microsoft.com/v1.0/")
            };

            string URI = $"users/a8f97275-2685-41ce-a61d-dc550cd090f8";

            httpClient.DefaultRequestHeaders.Remove("Authorization");
            httpClient.DefaultRequestHeaders.Add("Authorization", "Bearer " + token);
            HttpResponseMessage response = await httpClient.GetAsync(URI);

            var HttpsResponse = await response.Content.ReadAsStringAsync();
            //var JSONObject = JsonConvert.DeserializeObject<object>(HttpsResponse);

            //return response.StatusCode.ToString();
            return HttpsResponse;
        }
    }
}

Output:-

Now, Add this Function in your Azure static web app and call it along with the static web app URL as mentioned in my SO answer.