httpcontextaccessor null reference on app service but not debug

Question

I have a weird issue I can't explain.

I have a helper class in my Blazor Server Side app that does arb functions for my app. I added services.AddHttpContextAccessor(); in startup,

declared it in my helper class

public GlobalHelper(IHttpContextAccessor accessor, 
            IOptions<AzureADB2COptions> azureAdB2COptions,
            IConfiguration configuration
            
           )
        {
            _accessor = accessor;
            AzureAdB2COptions = azureAdB2COptions.Value;
            Configuration = configuration;
            
        }

and then have a function to return the userid:

 public string GetUserID()
    {
        var context = _accessor.HttpContext;


        return context.User.FindFirst(ClaimTypes.NameIdentifier).Value;

and then in my page, I just want to display it first on a button click event:

 @inject Classes.GlobalHelper _helper

<h1>Counter</h1>

<p>Current count: @currentCount</p>

<button class="btn btn-primary" @onclick="IncrementCount">Click me</button>


@code {

    string currentCount = "test";

    void IncrementCount()
    {
        var test4 = httpContextAccessor.HttpContext;

        var authState = AuthenticationStateProvider.GetAuthenticationStateAsync();
        var user = authState.Result.User;
        if (user.Identity.IsAuthenticated)
        {

            try
            {
            

                currentCount = _helper.GetUserID().Result;
                
            }
            catch (Exception ex)
            {

                currentCount = ex.ToString();
            }


        }
        else
        {
            Console.WriteLine("The user is NOT authenticated.");
        }


    }
}

If I just debug locally, this works fine. As soon as I publish this to an app service in Azure... I get a nullreferenceexception on accessing the httpcontextaccessor in the globalhelper class. This line:

return context.User.FindFirst(ClaimTypes.NameIdentifier).Value;

What could I be doing wrong so that the httpcontext is null in the app service and not in debug on my local machine?

Answer 1

The HttpContext is not available, at least most of the time, in Blazor Server App. You shouldn't try to access it, and you shouldn't use IHttpContextAccessor. Read more here: https://github.com/aspnet/AspNetCore/issues/14090 https://github.com/aspnet/AspNetCore/issues/13903 https://github.com/aspnet/AspNetCore/issues/12432#issuecomment-534315513 https://github.com/aspnet/AspNetCore/issues/5330#issuecomment-413928731

Note: You may access Authentication State in Blazor Server App via the AuthenticationStateProvider object and authorization components such as AuthorizeView, AuthorizeRouteView and CascadingAuthenticationState depending on what you want to do.