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gsosl's avatar
gsosl
Copper Contributor
Feb 17, 2024

Desktop app using REST endpoint returning 401 (Unauthorized) error

I ultimately want to upload files using SharePoint APIs, however initially I am reading a site's lists.   I have followed https://learn.microsoft.com/en-us/answers/questions/1391519/how-to-authenti...
tibhusha1070's avatar
tibhusha1070
Copper Contributor
Feb 18, 2024
Try to follow the below steps:
1. Delete the app from AppCatalog
2. Remove App from Recyclebin and Second state recyclebin of SharePoint.
3. Change the major version of app
4. Again upload the App and trust it.
5. Check the issue is resloved or not.

alternative approach, consider using the SharePoint PnP (Patterns and Practices) library. It provides a set of powerful tools and utilities for working with SharePoint, including authentication, REST API calls, and more.

using System;
using System.Security;
using OfficeDevPnP.Core.Authentication;
using Microsoft.SharePoint.Client;

class Program
{
static void Main(string[] args)
{
string siteUrl = "https://xxxxxxxxxxxxxxxx.sharepoint.com/sites/xxxxxxxx";
string clientId = "xxxxxxxx-5a22-4a98-9a14-4a4c37b9d13a";
string clientSecret = "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx";

var authManager = new AuthenticationManager();
using (var context = authManager.GetAppOnlyAuthenticatedContext(siteUrl, clientId, clientSecret))
{
context.Load(context.Web, w => w.Title);
context.ExecuteQuery();

Console.WriteLine($"Connected to site: {context.Web.Title}");

var lists = context.Web.Lists;
context.Load(lists, l => l.Include(li => li.Title));
context.ExecuteQuery();

Console.WriteLine("Lists in the site:");
foreach (var list in lists)
{
Console.WriteLine($"- {list.Title}");
}
}
}
}

  • gsosl's avatar
    gsosl
    Copper Contributor
    Feb 20, 2024

    tibhusha1070 thanks for your reply.

     

    The code I got this to work with:

     

    using System;
using System.Net.Http;
using System.Threading.Tasks;
using System.Collections.Generic;
using Newtonsoft.Json.Linq;

class Program
{
    static async Task Main(string[] args)
    {
        var siteId = "xxxxxxxx-ac84-4fc9-a4af-e880bbd4f1be";
        var tenantId = "xxxxxxxx-191b-4de1-806c-e26a6700397f";
        var clientId = "xxxxxxxx-2be7-4640-b03f-64b5c6c1f1d9";
        var clientSecret = "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx";

        var url = $"https://login.microsoftonline.com/{tenantId}/oauth2/v2.0/token";
        var client = new HttpClient();

        // Set the Accept header to application/json
        client.DefaultRequestHeaders.Accept.Clear();
        client.DefaultRequestHeaders.Accept.Add(new System.Net.Http.Headers.MediaTypeWithQualityHeaderValue("application/json"));

        // Form urlencoded values
        var values = new Dictionary<string, string>
        {
            { "grant_type", "client_credentials" },
            { "client_id", clientId },
            { "scope", "https://graph.microsoft.com/.default" },
            { "client_secret", clientSecret }
        };
        var content = new FormUrlEncodedContent(values);

        var response = await client.PostAsync(url, content);
        var jsonString = await response.Content.ReadAsStringAsync();

        var jsonObject = JObject.Parse(jsonString);
        var accessToken = jsonObject["access_token"].ToString();

        Console.WriteLine($"Access Token: {accessToken}");

        // Use the access token to authenticate to the REST endpoint
        var requestUrl = $"https://graph.microsoft.com/v1.0/sites/{siteId}/lists";
        client.DefaultRequestHeaders.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue("Bearer", accessToken);

        var apiResponse = await client.GetAsync(requestUrl);
        var apiJsonString = await apiResponse.Content.ReadAsStringAsync();

        Console.WriteLine($"API Response: {apiJsonString}");
    }
}

     

     

    The steps to register the app:

    1. Go to https://portal.azure.com/ or https://entra.microsoft.com/ -> App Registrations
    2. Select + New Registration, give a display name for the application and click Register
    3. Once the app is registered, note down the ClientId and TenantId from the page
      that appears. Then click on Add a certificate or secret
    4. Under Certificates & secrets, click on + New client secret. Enter a description for the client secret and click Add.
    5. Note down the Value of the client secret.
    6. Go to API Permissions. Click on + Add a permission
    7. Select Microsoft APIs -> Microsoft Graph
    8. Under Application permissions, select Sites.ReadWrite.All
    9. Select Grant admin consent for and approve it.
    10. https://<tenant-name>.sharepoint.com/sites/<TeamSite>/_api/site/id and note down the Site Id

    (Credit to Psiog Digital for those instructions.)

     

    Add-ins are being retired, authentication is done with Microsoft Entra ID.  I was able to get the PnP code to build with the deprecated `SharePointPnPCoreOnline` DLL (I didn't attempt .net8), but got a `Microsoft.SharePoint.Client.ServerUnauthorizedAccessException: Access is denied.` error.

     

    I have to say I have never had so much trouble using a REST API.  The documentation is Greek.  The architecture is a can of worms.  The books are not current or up-to-date.  Do you have to be a Microsoft Certified Engineer to upload a file using a REST endpoint!?  One shouldn't.

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