How to access the HttpServerUtility.MapPath method in a Thread or Timer?

Question

I use a System.Timers.Timer in my Asp.Net application and I need to use the HttpServerUtility.MapPath method which seems to be only available via <

Answer 1

It's possible to use HostingEnvironment.MapPath() instead of HttpContext.Current.Server.MapPath()

I haven't tried it yet in a thread or timer event though.

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Some (non viable) solutions I considered;

• The only method I care about on HttpServerUtility is MapPath. So as an alternative I could use AppDomain.CurrentDomain.BaseDirectory and build my paths from this. But this will fail if your app uses virtual directories (Mine does).

• Another approach: Add all the paths I need to the the Global class. Resolve these paths in Application_Start.

Answer 2

Can you not call the MapPath function before starting the timer, and simply cache the result? Is it absolutely neccessary to have the MapPath call inside the tick event?

Answer 3

I think the reason for why it is null at that time (if you think about it), is that the timer elapsed event doesn't occur as part of a HTTP request (hence there is no context). It is caused by something on your server.

Answer 4

When the timer elapse, there is no current HTTP context. This is because the timer events are not related to a specific HTTP request.

What you should do is use HttpServerUtility.MapPath where HTTP context is available. You can do it in one of the request pipeline events (such as Page_Load) or in a Global.asax event such as Application_Start.

Assign the MapPath result to a variable accessible from the Timer.Elapsed event, where you could use Path.Combine to get the location of a specific file you need.

Answer 5

I don't know if this will solve your virtual directories issue, but I use this for MapPath:

public static string MapPath(string path)
{
    if (HttpContext.Current != null)
        return HttpContext.Current.Server.MapPath(path);

    return HttpRuntime.AppDomainAppPath + path.Replace("~", string.Empty).Replace('/', '\\');
}

Answer 6

HostingEnvironment isn't the perfect solution because it's a very difficult class to mock (see How to unit test code that uses HostingEnvironment.MapPath).

For those who need testability, a better way might be to create your own path-mapper interface as proposed by https://stackoverflow.com/a/1231962/85196, except implement it as

public class ServerPathMapper : IPathMapper { 
 public string MapPath(string relativePath) { 
      return HostingEnvironment.MapPath(relativePath); 
 } 
} 

The result is easily mockable, uses HostingEnvironment internally, and could even potentially address ase69s's concern at the same time.