System.Threading.ReaderWriterLockSlim.EnterUpgradeableReadLock C# (CSharp) Method

		public void EnterUpgradeableReadLock ()
		{
			TryEnterUpgradeableReadLock (-1);
		}

 private HttpStatusCode CancelCrossing(CrossingRequest cross)
 {
     m_crossLock.EnterUpgradeableReadLock();
     try
     {
         if (m_crossings.ContainsKey(cross.uuid))
         {
             m_crossLock.EnterWriteLock();
             try
             {
                 m_crossings.Remove(cross.uuid);
                 return(HttpStatusCode.OK);
             }
             finally
             {
                 m_crossLock.ExitWriteLock();
             }
         }
         else
         {
             return(HttpStatusCode.NotFound);
         }
     }
     finally
     {
         m_crossLock.ExitUpgradeableReadLock();
     }
 }