mcs/class/System.Web.Mvc3/Mvc/UrlRewriterHelper.cs

   1 namespace System.Web.Mvc {
   2     using System.Collections.Specialized;
   3
   4     internal class UrlRewriterHelper {
   5         private const string _urlWasRewrittenServerVar = "IIS_WasUrlRewritten";
   6         private const string _urlRewriterEnabledServerVar = "IIS_UrlRewriteModule";
   7
   8         private object _lockObject = new object();
   9         private bool _urlRewriterIsTurnedOnValue;
  10         private bool _urlRewriterIsTurnedOnCalculated = false;
  11
  12         private static bool WasThisRequestRewritten(HttpContextBase httpContext) {
  13             NameValueCollection serverVars = httpContext.Request.ServerVariables;
  14             bool requestWasRewritten = (serverVars != null && serverVars[_urlWasRewrittenServerVar] != null);
  15             return requestWasRewritten;
  16         }
  17
  18         private bool IsUrlRewriterTurnedOn(HttpContextBase httpContext) {
  19             // Need to do double-check locking because a single instance of this class is shared in the entire app domain (see PathHelpers)
  20             if (!_urlRewriterIsTurnedOnCalculated) {
  21                 lock (_lockObject) {
  22                     if (!_urlRewriterIsTurnedOnCalculated) {
  23                         NameValueCollection serverVars = httpContext.Request.ServerVariables;
  24                         bool urlRewriterIsEnabled = (serverVars != null && serverVars[_urlRewriterEnabledServerVar] != null);
  25                         _urlRewriterIsTurnedOnValue = urlRewriterIsEnabled;
  26                         _urlRewriterIsTurnedOnCalculated = true;
  27                     }
  28                 }
  29             }
  30             return _urlRewriterIsTurnedOnValue;
  31         }
  32
  33         public virtual bool WasRequestRewritten(HttpContextBase httpContext) {
  34             return IsUrlRewriterTurnedOn(httpContext) && WasThisRequestRewritten(httpContext);
  35         }
  36     }
  37 }