using System;

using Microsoft.IdentityModel.Clients.ActiveDirectory;

using System.Net;

public class Program

{

    public static void Main()

    {

        var serviceUrl = "https://dwuat.crm4.dynamics.com/XRMServices/2011/Organization.svc/web?SdkClientVersion=6.1.0.533";

        // Use AuthenticationParameters to send a request to the organization's endpoint and

        // receive tenant information in the 401 challenge. 

        AuthenticationParameters parameters = null;

        HttpWebResponse response = null;

        try

        {

            // Create a web request where the authorization header contains the word "Bearer".

            HttpWebRequest httpWebRequest = (HttpWebRequest) WebRequest.Create(serviceUrl);

            httpWebRequest.Headers.Add(HttpRequestHeader.Authorization.ToString(), "Bearer");

            // The response is to be encoded.

            httpWebRequest.ContentType = "application/x-www-form-urlencoded";

            response = (HttpWebResponse) httpWebRequest.GetResponse();

            // If the expected response is returned, this coAdalExceptione should not execute.

            throw new Exception("unauthorized_response_expected. Unauthorized http response (status code 401) was expected");

        }

        catch (WebException ex)

        {

            Console.WriteLine("Exception: " + ex.Message);

            response = (HttpWebResponse) ex.Response;

            if (response == null)

            {

                throw new Exception(

                    "Unauthorized Http Status Code (401) was expected in the response",

                    (Exception) ex);

            }

            else

            {

                // A good response was returned. Extract any parameters from the response.

                // The response should contain an authorization_uri parameter.

                parameters = AuthenticationParameters.CreateFromUnauthorizedResponse(response);

                Console.WriteLine("Resource:" + parameters.Resource);

            }

        }

        finally

        {

            if (response != null)

                response.Close();

        }

        // Return the authority URL.

        Console.WriteLine("Authority:" + parameters.Authority);

    }

}