Rule Definition
Applications, having threads that try to acquire a lock, on an object that has a weak identity, can have reliability issues. This is because the thread can be blocked by a second thread in a different application domain that has a lock on the same object. An object is said to have a weak identity when it can be directly accessed across application domain boundaries. The following types have a weak identity and are flagged by the rule: * MarshalByRefObject * ExecutionEngineException * OutOfMemoryException * StackOverflowException * String * MemberInfo * ParameterInfo * Thread

Remediation
Try and avoid using weak identities.

Violation Code Sample

using System;
using System.IO;
using System.Reflection;
using System.Threading;

namespace ReliabilityLibrary
{
   class WeakIdentities
   {
      void LockOnWeakId1()
      { 
         lock(typeof(WeakIdentities)) {}
      }

      void LockOnWeakId2() 
      {
         MemoryStream stream = new MemoryStream();
         lock(stream) {} 
      }
}

Fixed Code Sample

using System; using System.IO; using System.Reflection; using System.Threading;  namespace ReliabilityLibrary {    class WeakIdentities    {       void LockOnWeakId2()        {          Object obj = new Object()          MemoryStream stream = new MemoryStream();          lock(obj) {}        } }

http://msdn.microsoft.com/en-us/library/ms182290.aspx