如何从HttpActionExecutedContext获取当前的HttpContext

Question

I'm writing an exception filter that will log exceptions to Elmah, so I'm doing something like this:

class ExceptionLoggingFilter : System.Web.Http.Filters.IExceptionFilter
{
    public Task ExecuteExceptionFilterAsync(HttpActionExecutedContext actExecContext, 
                                            CancellationToken cancellationToken)
    {
        var httpContext = // what do I do here?
        var errorSignal = ErrorSignal.FromContext(httpContext); // this is Elmah
        errorSignal.Raise(actExecContext.Exception, httpContext);
    }
}

My problem is that I don't know what to put in place of the comment question. I've tried to explore the member tree of the HttpActionExecutedContext that I get from the method signature to find a way to a System.Web.HttpContext , but I can't find any way to get there.

How do I accomplish my goal here?

Answer 1

Elmah.ErrorSignal.FromCurrentContext()

uses HttpContext.Current under the hood, so although that might have worked I did find a better (albeit more roundabout) way to get to it:

var request = actionExecutedContext.Request;
object value;
if (request == null
    || !request.Properties.TryGetValue("MS_HttpContext", out value)
    || !(value is HttpContextBase))
    return null; // Actually I'm returning a Maybe monad here but that's off topic...
}
var httpContextBase = value as HttpContextBase;
return httpContextBase.ApplicationInstance.Context;

I'm using this together with a maybe monad implementation that lets me use ErrorSignal.FromCurrentContext() as fallback, and so far it's worked well.

Answer 2

Note this will probably only work when the WebAPI is hosted in IIS (not self-hosted):

class ExceptionLoggingFilter : System.Web.Http.Filters.IExceptionFilter
{
    public Task ExecuteExceptionFilterAsync(HttpActionExecutedContext actExecContext, 
                                            CancellationToken cancellationToken)
    {
        //var httpContext = // what do I do here? NOTHING
        var errorSignal = ErrorSignal.FromCurrentContext(); // this is Elmah
        errorSignal.Raise(actExecContext.Exception);
    }
}