HttpContext "Decoraptor" for ASP.NET MVC 5 - https://blog.ploeh.dk/2014/08/24/decoraptor/

FeatureAContextProvider.cs

public class FeatureAContextProvider : IFeatureContextProvider<FeatureAContext>
{
    private readonly HttpContextBase _httpContext;

    public FeatureAContextProvider(HttpContextBase httpContext)
    {
        // this would be a "decoraptor" (in quotes because it's wrapping ambient context 🤢)
        _httpContext = httpContext;
    }

    public FeatureAContext GetContext()
    {
        return new FeatureAContext
        {
            Foo = _httpContext.Request.Headers["Foo"]
        };
    }
}

FeatureBContextProvider.cs

public class FeatureBContextProvider : IFeatureContextProvider<FeatureBContext>
{
    private readonly IConfiguration _config;

    public FeatureBContextProvider(IConfiguration config)
    {
        _config = config;
    }

    public FeatureBContext GetContext()
    {
        return new FeatureBContext
        {
            Bar = _config["Bar"]
        };
    }
}

HttpContextDecoraptor.cs

public class HttpContextDecoraptor : HttpContextBase
{
	private readonly Func<HttpContextBase> _httpContextFactory;

	public HttpContextDecoraptor(Func<HttpContextBase> httpContextFactory)
	{
		_httpContextFactory = httpContextFactory;
	}

	public override HttpRequestBase Request => _httpContextFactory().Request;

	/* ... remaining overrides ... */
}

Usage - Global.asax.cs

var httpContextDecoraptor = new HttpContextDecoraptor(
	httpContextFactory: () => new HttpContextWrapper(HttpContext.Current));

var featureAContextProvider = new FeatureAContextProvider(httpContextDecoraptor);

config.Filters.Add(new FeatureGateFilter(featureAContextProvider));