静态方法线程安全

Question

Let's say I call the following method when a user logs into my mvc application:

public static bool IsValidBrowser()
{
    var browser = HttpContext.Current.Request.Browser;

    if (browser.Browser == "IE") {
        if (browser.MajorVersion < 10) {
            return false;
        }
    }
    return true;
}

Is this method thread safe? Obviously I'm not modifying anything here, but might it be possible that HttpContext.Current changes in the middle of this method?

Would writing the code this way make it thread safe?

public ActionResult Login () 
{
    bool validBrowser = IsValidBrowser(HttpContext.Current.Request.Browser);
}

public static bool IsValidBrowser(HttpBrowserCapabilities browser)
{
    if (browser.Browser == "IE") {
        if (browser.MajorVersion < 10) {
            return false;
        }
    }
    return true;
}

Answer 1

HttpContext.Current本身是一个静态方法，它将从当前线程返回上下文，因此您无需担心。

Answer 2

Is this method thread safe?

Yes this method is thread safe as @DoctorMick already explained. Adding one more point.

Microsoft's Framework Class Library (FCL) guarantees that all static methods are thread safe. The FCL had to do this internally because there is no way that multiple companies producing different assemblies could coordinate on a single lock for arbitrating access to the resource.

So if you are using FCL static method you don't need to think about thread safety. eg(Console Class, Math class etc.)