Why is IHttpContextAccessor.HttpContext sometimes null?

Question

Using .Net Core 2.2, I'm using HttpClient to call an API, along with an Http Message Handler. The message handler injects IHttpContextAccessor, but that object sometimes contains an HttpContext property that is null - I can't understand why that would ever be null.

Here's the service registration in startup:

services.AddTransient<HttpClientTokenHandler>();

services.AddHttpClient("client", c =>
    {
        c.BaseAddress = new Uri(options.ApiUrl.TrimEnd('/') + '/');
    }).AddHttpMessageHandler<HttpClientTokenHandler>();

services.AddHttpContextAccessor();

And the token handler implementation where HttpContext is sometimes null.

public HttpClientTokenHandler(IHttpContextAccessor context)
{
    _context = context;
}

protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
{    
    var access_token = await _context.HttpContext.GetTokenAsync(Constants.TokenTypes.AccessToken);

    if (!string.IsNullOrEmpty(access_token))
    {
        request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", access_token);
    }
    var response = await base.SendAsync(request, cancellationToken);
    return response;
}

What could cause _context.HttpContext to be null, when it's simply being injected?

Just for clarification, is `_context` null? Or the property `HttpContext` null? — mxmissile, Dec 18 '19 at 20:47
@mxmissile only the ```HttpContext``` property is null, ```_context``` is not null — Jeremy Maddrey, Dec 18 '19 at 20:53
`IHttpContextAccessor` is only available if you call `services.AddHttpContextAccessor();` in `ConfigureServices`, which your code isn't doing. — Ian Kemp, Dec 18 '19 at 22:23
@IanKemp fair point, i pared down the startup and failed to put that in the question. thanks for catching that. — Jeremy Maddrey, Dec 19 '19 at 13:50
Same problem for me, I forgot to call services.AddHttpContextAccessor(); in one of the microservices, thanks @IanKemp — Zaha, Dec 03 '21 at 02:03

Why is IHttpContextAccessor.HttpContext sometimes null?

0 Answers0