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return 401 response from asp.net with iis hosting with windows auth enabled

We have asp.net api hosted in iis with windows auth enabled and allow anonymous access.
Its seems that when I return 401 response from api, IIS intercept it and trying to negotiate with browser for windows auth without ending current "request-response" (in that moment in browser popups windows auhth window, asking for credentials). At first, I'm wonder what should happen next if i provide valid creds? In asp pipiline request already ended at this moment. And in second - is it possible for just return 401 to browser without iis intercept it? Maybe some options in config or something?

You can try the following methods to solve the problem:
Open IIS and select the website (or directory) that is causing the
401
Open the “Authentication” property under the IIS header
Click the “Windows Authentication” item and click Providers
Change the order and put NTLM on top.
After the change open Command Prompt and do a iisreset /noforce.

Web API Service Fabric app gives unauthorized

I have created a web api hosted in service fabric. When I hit the api from client it works fine on local but is giving 401 from remote machine. I have used IntegratedWindowsAuthentication and Negotiate authentication schemes in Web API.
Can someone help on this?

Your problem is that the remote machine doesn't know about the windows account on your client so it throws a 401. Try creating an account on the remote machine with the same username and password and try again.

Web API 2 returns 401 when hosted on IIS and return 200 when set authentication to anonymous

I have a WebApi project , which returns some data , this works fine when we query through the URL , but returns 401 when i invoke it from my console app.
this project has been hosted in IIS 8 and i need this to run under windows authentication. If i set it to anonymous authentication then works fine, but gives error to windows auth mode. Thanks in advance.

Check HTTP Status Codes RFC ...401 stands for Unauthorized Access means while invoking from your console app you are not passing the Authorization header in your API request.

Check this out(it has info on using windows authentication with web API):
https://www.codeproject.com/tips/996401/authenticate-webapis-with-basic-and-windows-authen

Request failed with http status 403 forbidden -Webservice-while calling the service via iis

Iam a beginer in c# .currently iam working on a api in which the request AND response are working properly(Visual studio)
But when it was published in the same pc's iis(iis 7) one error is getting AS " the request failed with http status 403 forbidden"
.Api uses ssl certificate also.
Whats wrong? Any help would be appreciated.

It depends on what user is being used for the service and whether that user is being allowed authentication. You left out a lot details out about your IIS configuration. Out of the box, IIS rarely serves ASPX without some adjustments.

WCF REST returning 401 Not authorize response with Windows Authentication

I have two applications:
Web Application deployed at Windows Server 2008 R2 server. This application serves as endpoint for WCF REST calls.
Windows Forms Desktop C# application which will make REST calls to web application above. This application is also running on same Windows Server 2008 R2 server machine.
Everything works fine if I have the Web application using Forms Authentication but as I change its authentication to Windows, the REST calls stop working and it starts getting 401 not authorized response from Web application.
Here are some details of my web application:
The WebHttpBinding for WCF is set to "WebHttpSecurityMode.TransportCredentialOnly" with credentials as HttpClientCredentialType.Windows.
this.Security.Mode = WebHttpSecurityMode.TransportCredentialOnly;
this.Security.Transport.ClientCredentialType = HttpClientCredentialType.Windows;
Web.config of this website is having:
<authentication mode="Windows" />
<authorization>
<deny users="?" />
</authorization>
IIS authentication setting for this site:
Providers for Windows Authentication is set to "Negotiate":
To investigate further I tried to debug the application and noticed that the REST calls are able to reach the BeginRequest method of Global.asax but after executing that method the 401 response is returned to client. I am not able to reach even to the ServiceAuthorizationManager as the 401 response is returned before that.
I have tried all the following WCF REST calls: GET, PUT and POST to this application from Windows Forms C# client and all of them are returned as 401 Not authorized from server.
The same C# client gets the desired response from web application works when I change the authentication mode of web application from Windows to Forms.
I would like to add more information on the above case.
Even with the Windows Authentication mode of web application if I try to request the server with a REST call directly via web browser (Chrome in my case) I can get the response. The issue is coming only when I make the REST call from C# Windows Forms client. I guess it works in this case where I make REST call directly from browser because the Browser must be sending some authorization header to the server to process the request.
Can you help me with the case where REST calls are made from a client other than browser?
How do I let the REST calls from clients to hit the WCF REST end points instead of being getting 401 responses from server?