Azure Active Directory question - C# Discussion Boards

31-Jul-20 0:50

Hi all I have this method in a class which tries to get an access token from Azure Active Directory - it works if I use it in a Net Core app but hangs forever when I try to use it in a Winforms app

private async Task GetAccessToken()
       {
            // Utils.GetAppConfigSetting just reads keys in App.config
           string Instance = Utils.GetAppConfigSetting("Instance");
           string TenantID = Utils.GetAppConfigSetting("TenantID");
           string ClientID = Utils.GetAppConfigSetting("ClientID");
           string ClientSecret = Utils.GetAppConfigSetting("ClientSecret");
           string BaseAddress = Utils.GetAppConfigSetting("BaseAddress");
           string ResourceID = Utils.GetAppConfigSetting("ResourceID");
           string APIServer = Utils.GetAppConfigSetting("APIServer");
           string Authority = String.Format(CultureInfo.InvariantCulture,Instance, TenantID);

           this.App = ConfidentialClientApplicationBuilder.Create(ClientID)
               .WithClientSecret(ClientSecret)
               .WithAuthority(new Uri(Authority))
               .Build();

           this.ResourceIds = new string[] { ResourceID };

           // this is where it hangs !!
           this.Result = await this.App.AcquireTokenForClient(this.ResourceIds).ExecuteAsync();
           this.AccessToken = this.Result.AccessToken;

           // this.Client is a RestSharp client
           this.Client.Authenticator = new JwtAuthenticator(this.AccessToken);
       }

// I call it with this code

this.GetAccessToken().GetAwaiter().GetResult();

there is no error it just hangs - any ideas ?

Edit

It must be the UI thread in Winforms as I just tried the same code in a Console App and it worked perfectly

"We can't stop here - this is bat country" - Hunter S Thompson - RIP

modified 31-Jul-20 9:51am.

Richard Deeming4-Aug-20 0:01

4-Aug-20 0:01

pkfox wrote:
It must be the UI thread in Winforms

Correct. Your async method tries to return to the current "execution context" after the await. In a WinForms app, when the async method was called from the UI thread, it tries to return to the UI thread. But you've blocked the UI thread by trying to execute the async method synchronously:

this.GetAccessToken().GetAwaiter().GetResult(); // Blocks the UI thread

Therefore, the async method can never complete.

If you're not accessing the UI from your GetAccessToken method, you can add .ConfigureAwait(false) to your ExecuteAsync call, so that the rest of the method can complete on a thread-pool thread:

this.Result = await this.App.AcquireTokenForClient(this.ResourceIds).ExecuteAsync().ConfigureAwait(false);

Otherwise, you'll need to find a way to avoid blocking the UI thread. You'd need to make the calling method async. However, you want to avoid async void methods[^]. A simple solution is to move the code into a task-returning async method, and assign the returned task to a "discard" variable to avoid the compiler warning.

Old code, don't use:

private void ButtonClick(object sender, EventArgs e)
{
    // Some code...
    this.GetAccessToken().GetAwaiter().GetResult();
    // Some more code...
}

Bad fix, don't use:

private async void ButtonClick(object sender, EventArgs e)
{
    // Some code...
    await this.GetAccessToken();
    // Some more code
}

Better fix:

private void ButtonClick(object sender, EventArgs e)
{
    _ = SomeMethodAsync();
}

private async Task SomeMethodAsync()
{
    // Some code...
    await this.GetAccessToken();
    // Some more code
}

ConfigureAwait FAQ | .NET Blog[^]

"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer

pkfox4-Aug-20 3:36

4-Aug-20 3:36

Thanks Richard should I leave the code as is in GetAccessToken() ? I got around it by using a BackGroundWorker but I think maybe your way is better

"We can't stop here - this is bat country" - Hunter S Thompson - RIP

Richard Deeming4-Aug-20 3:40

4-Aug-20 3:40

If you're moving the code to a task-returning async method, and getting rid of the .GetAwaiter().GetResult() call in favour of awaiting the operation, then the GetAccessToken code should be fine.

"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer

pkfox4-Aug-20 5:38

4-Aug-20 5:38

How will I know when the job has finished ?

"We can't stop here - this is bat country" - Hunter S Thompson - RIP

Richard Deeming4-Aug-20 5:48

4-Aug-20 5:48

That depends what you're trying to do.

If you just want to run some code immediately after GetAccessToken has finished, you can put it in the new async method after the await this.GetAccessToken(); line.

"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer

pkfox4-Aug-20 6:52

4-Aug-20 6:52

Except GetAccessToken() is in a separate class from the form

"We can't stop here - this is bat country" - Hunter S Thompson - RIP

Richard Deeming4-Aug-20 23:14

4-Aug-20 23:14

That doesn't matter. You have a task-returning async method which calls it, and put any code you need to run after it's returned after the await.

If you need to run code in the form after the async method in another class returns, you also use a task-returning async method, and put the code after the await.

class SomeClass
{
    private async Task GetAccessToken() { ... }
    
    public async Task DoSomething()
    {
        // Code to run in this class before getting the access token here...
        
        await GetAccessToken();
        
        // Code to run in this class after getting the access token here...
    }
}

class YourForm
{
    private SomeClass _someClass;
    
    private void FormLoad(object sender, EventArgs e)
    {
        _someClass = new SomeClass();
        _ = DoSomethingInTheForm();
    }
    
    private async Task DoSomethingInTheForm()
    {
        // Code to run in the form before getting the access token here...
        
        await _someClass.DoSomething();
        
        // Code to run in the form after getting the access token here...
    }
}

"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer

pkfox5-Aug-20 3:12

5-Aug-20 3:12

Thanks Richard that's pretty much what I've ended up with - brilliant article in the link you posted

"We can't stop here - this is bat country" - Hunter S Thompson - RIP

pkfox4-Aug-20 23:12