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Important This document may not represent best practices for current development, links to downloads and other resources may no longer be valid. Current recommended version can be found here.

Do not lock on objects with weak identity

TypeName

DoNotLockOnObjectsWithWeakIdentity

CheckId

CA2002

Category

Microsoft.Reliability

Breaking Change

NonBreaking

A thread attempts to acquire a lock on an object that has a weak identity.

An object is said to have a weak identity when it can be directly accessed across application domain boundaries. A thread that tries to acquire a lock on an object that has a weak identity can be blocked by a second thread in a different application domain that has a lock on the same object. The following types have a weak identity and are flagged by the rule:

To fix a violation of this rule, use an object from a type that is not in the list in the Description section.

Do not exclude a warning from this rule.

The following example shows some object locks that violate the rule.

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) {} 
      }

      void LockOnWeakId3() 
      { 
         lock("string") {} 
      }

      void LockOnWeakId4() 
      { 
         MemberInfo member = this.GetType().GetMember("LockOnWeakId1")[0];
         lock(member) {} 
      }
      void LockOnWeakId5()
      {
         OutOfMemoryException outOfMemory = new OutOfMemoryException();
         lock(outOfMemory) {}
      }
   }
}

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