如何访问线程或定时器中的 HttpServerUlity.MapPath 方法？

我在我的 Asp 中使用 System.Timers.Timer。Net 应用程序和我需要使用的 HttpServerUtility.MapPath方法，似乎只有通过 HttpContext.Current.Server.MapPath可用。 问题是，当 Timer.Elapsed事件触发时，HttpContext.Current是 null。

还有其他获取对 HttpServerUtilityobject 的引用的方法吗？ 我可以把它注入到类的构造函数中。安全吗？我如何确定它不会在当前请求的末尾被垃圾收集？

谢谢！

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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.

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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?

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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.

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最佳答案

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.

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.

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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('/', '\\');
}
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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.


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