CA2002: Do not lock on objects with weak identity

Cause

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

Rule Description

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:

• MarshalByRefObject

• ExecutionEngineException

• OutOfMemoryException

• StackOverflowException

• String

• MemberInfo

• ParameterInfo

• Thread

How to Fix Violations

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

When to Suppress Warnings

Do not suppress a warning from this rule.

Related Rules

CA2213: Disposable fields should be disposed

Example

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) {}
      }
   }
}

Imports System
Imports System.IO
Imports System.Reflection
Imports System.Threading

Namespace ReliabilityLibrary

   Class WeakIdentities
   
      Sub SyncLockOnWeakId1()

         SyncLock GetType(WeakIdentities)
         End SyncLock

      End Sub

      Sub SyncLockOnWeakId2() 
      
         Dim stream As New MemoryStream()
         SyncLock stream
         End SyncLock

      End Sub

      Sub SyncLockOnWeakId3() 
       
         SyncLock "string"
         End SyncLock

      End Sub

      Sub SyncLockOnWeakId4() 
       
         Dim member As MemberInfo = _
            Me.GetType().GetMember("SyncLockOnWeakId1")(0)
         SyncLock member
         End SyncLock

      End Sub

      Sub SyncLockOnWeakId5()
      
         Dim outOfMemory As New OutOfMemoryException()
         SyncLock outOfMemory
         End SyncLock

      End Sub

   End Class

End Namespace

See Also

Monitor AppDomain lock Statement SyncLock Statement