NullReferenceException in Microsoft.IdentityModel.Clients.ActiveDirectory.AcquireToken - azure

Question

I'm trying to get some MSFT Power BI SDK samples working. Unfortunately, the Microsoft.IdentityModel.Clients.ActiveDirectory library is giving me a lot of trouble with the initial external authentication step.
I'm using Microsoft.IdentityModel.Clients.ActiveDirectory, Version=2.28.3.860, from NuGet; this is the last version of the library before AcquireToken was removed, and I haven't figured out how to use its replacement (AcquireTokenAsync) in a way that's equivalent to what I see in the samples.
When I take the following code and modify the TODO lines to specify my actual Azure Client ID and authentication redirect page, I get as far as the AcquireToken line.
using System;
using Microsoft.IdentityModel.Clients.ActiveDirectory;
public class Application
{
public static void Main(string[] args)
{
try
{
string clientID = "abcdef01-1234-1234-abcd-abcdabcd1234"; // TODO: actual Azure client ID
string redirectUri = "https://acmecorporation.okta.com/login/do-login"; // TODO: actual redirect
string resourceUri = "https://analysis.windows.net/powerbi/api";
string authorityUri = "https://login.windows.net/common/oauth2/authorize";
AuthenticationContext authContext = new AuthenticationContext(authorityUri);
AuthenticationResult ar = authContext.AcquireToken(
resourceUri,
clientID,
new Uri(redirectUri),
PromptBehavior.RefreshSession);
string token = ar.AccessToken;
Console.WriteLine("Success: " + token);
}
catch (Exception ex)
{
Console.WriteLine(ex.ToString());
}
}
}
At this point:
A "Sign in to your account" window pops up with the name of the app I've associated in Azure with the clientID GUID
I'm redirected to my organization's ("acmecorporation") sign-on page
I sign in using my AD credentials
The AcquireToken method throws the following NullReferenceExpection:
System.NullReferenceException: Object reference not set to an instance of an object.
at Microsoft.IdentityModel.Clients.ActiveDirectory.AuthenticationContext.RunAsyncTask[T](Task`1 task)
at Microsoft.IdentityModel.Clients.ActiveDirectory.AuthenticationContext.AcquireToken(String resource, String clientId, Uri redirectUri, PromptBehavior promptBehavior)
at PowerBISample.Application.Main(String[] args) in \\noxfile\users\ehirst\documents\visual studio 2015\Projects\PowerBISample\PowerBISample\Program.cs:line 18
Can anyone provide guidance on how to get past this? My goal is to get a POC working to determine whether we can integrate Power BI into a larger application, but so far it feels like I'm beta testing a pretty unstable system.

Answer 1

The NullReferenceException is a bug in the 2.x version of the ADAL library; it's fixed in current versions. It was triggered by an incorrect value of redirectUri; unfortunately the documentation was sparse on this one. A working code sample, adapted (thanks Kanishk!) to use the current 3.13.7 version of ADAL, is posted below.
namespace PowerBISample
{
using System;
using Microsoft.IdentityModel.Clients.ActiveDirectory;
using System.Threading.Tasks;
public class Application
{
public static void Main(string[] args)
{
Run();
Console.ReadLine();
}
static async void Run()
{
try
{
string clientID = "abcdef01-1234-1234-abcd-abcdabcd1234"; // TODO: actual Azure client ID
/** THE REAL PROBLEM WAS HERE **/
string redirectUri = "https://login.live.com/oauth20_desktop.srf";
string resourceUri = "https://analysis.windows.net/powerbi/api";
string authorityUri = "https://login.windows.net/common/oauth2/authorize";
AuthenticationContext authContext = new AuthenticationContext(authorityUri);
AuthenticationResult ar = await authContext.AcquireTokenAsync(resourceUri, clientID, new Uri(redirectUri), new PlatformParameters(PromptBehavior.RefreshSession));
string token = ar.AccessToken;
Console.WriteLine("Success: " + token);
}
catch (Exception ex)
{
string error = ex.ToString();
Console.WriteLine(error);
}
}
}
}