SharePoint 2019 Search REST API Is Returning 401 Unauthorized - When Called from C# Using Basic Authorization Request Header

Question

I have my own C# Web API service (targeting .NET 5.0) that is sitting on the same server where an on-premise SharePoint 2019 is located. My code calls the built-in SharePoint REST API in order to do searches and return results (the outside world will only be accessing my service).

I have no problem calling the SharePoint REST API from IE on that server.

Within my Web API service (https) I call the SharePoint Rest service (http) using the same url that worked in IE

using (var client = new HttpClient())
{
     client.BaseAddress = new Uri(sharePointSearchServiceBaseUrl); 
     client.DefaultRequestHeaders.Clear();
     client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));

     var plainTextBytes = System.Text.Encoding.UTF8.GetBytes("account:password");
     string val = System.Convert.ToBase64String(plainTextBytes);
     client.DefaultRequestHeaders.Add("Authorization", "Basic " + val);

     HttpResponseMessage response = await client.GetAsync("search/query?querytext='(oil*)'&rowlimit=100");

     if (response.IsSuccessStatusCode) 
     {
        var objResponse = response.Content.ReadAsStringAsync().Result;                        
        return Content(objResponse);
     }
    

Unfortunately, the results from the client.GetAsync are always as follows:

INFO 2021-01-07 01:24:18 StatusCode: 401, ReasonPhrase: 'Unauthorized' , Version: 1.1, Content: System.Net.Http.HttpConnectionResponseContent, Headers: { Server: Microsoft-IIS/10.0 SPRequestGuid: 47049f9f-8244-1032-40ac-07df48a24632 request-id: 47049f9f-8244-1032-40ac-07df48a24632 X-Frame-Options: SAMEORIGIN SPRequestDuration: 6 SPIisLatency: 2 WWW-Authenticate: NTLM X-Powered-By: ASP.NET MicrosoftSharePointTeamServices: 16.0.0.10368 X-Content-Type-Options: nosniff X-MS-InvokeApp: 1; RequireReadOnly Date: Thu, 07 Jan 2021 18:24:18 GMT Content-Length: 0 }

I have tried passing all SharePoint accounts I have, and all of them have given me the same 401.

Any insight into resolving this would be much appreciated.

Answer 1

I was able to find a solution for this. The most important line is the NetworkCredential one. I tried many other approaches, but this is the only one that worked for me.

using (var handler = new HttpClientHandler())
   {
            handler.Credentials =  new NetworkCredential(account, password, domain); 
            using (var client = new HttpClient(handler))
            {
                var requri = new Uri("http://localhost:30001/_api/search/query?querytext='(oil*)'&rowlimit=100");
                HttpResponseMessage response = await client.GetAsync(requri);

                if (response.IsSuccessStatusCode)
                {
                    var objResponse = response.Content.ReadAsStringAsync().Result;
                    _logger.LogInformation("Results are: " + objResponse);
                    return Content(objResponse);
                }
                else
                {
                    _logger.LogInformation("Sharepoint service call - was NOT successful");
                    _logger.LogInformation(response.ToString());
                    return null;
                }
            }
        }