Do not lock on objects with weak identity







Breaking Change

Non Breaking


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:

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.


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

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 = _
         SyncLock member
         End SyncLock 

      End Sub 

      Sub SyncLockOnWeakId5()

         Dim outOfMemory As New OutOfMemoryException()
         SyncLock outOfMemory
         End SyncLock 

      End Sub 

   End Class 

End Namespace
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) {}

See Also


lock Statement (C# Reference)

SyncLock Statement