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Code Analyzer for VB.NET

There is a newer version: 10.5.0.109200

Why is this an issue?
To prevent potential deadlocks in an application, it is crucial to release any locks that are
acquired within a method along all possible execution paths.
Failing to release locks properly can lead to potential deadlocks, where the lock might not be released, causing issues in the application.
This rule specifically focuses on tracking the following types from the System.Threading namespace:

   Monitor 
   Mutex 
   ReaderWriterLock 
   ReaderWriterLockSlim 
   SpinLock  

An issue is reported when a lock is acquired within a method but not released on all paths.
Exceptions
If the lock is never released within the method, no issue is raised, assuming that the callers will handle the release.
How to fix it
To make sure that a lock is always released correctly, you can follow one of these two methods:

   Use a SyncLock statement
  with your lock object. 
   Use a Try-Finally
  statement and put the release of your lock object within a Finally block. 

Code examples
Noncompliant code example
Class Example
    Private obj As Object = New Object()

    Public Sub DoSomethingWithMonitor()
        Monitor.Enter(obj) ' Noncompliant: not all paths release the lock

        If IsInitialized() Then
            ' ...
            Monitor.Exit(obj)
        End If
    End Sub
End Class

Class Example
    Private lockObj As ReaderWriterLockSlim = New ReaderWriterLockSlim()

    Public Sub DoSomethingWithReaderWriteLockSlim()
        lockObj.EnterReadLock() ' Noncompliant: not all paths release the lock
        If IsInitialized() Then
            ' ...
            lockObj.ExitReadLock()
        End If
    End Sub
End Class

Compliant solution
Class Example
    Private obj As Object = New Object()

    Public Sub DoSomethingWithMonitor()
        SyncLock obj ' Compliant: the lock will be released at the end of the SyncLock block
            If IsInitialized() Then
                ' ...
            End If
        End SyncLock
    End Sub
End Class

Class Example
    Private lockObj As ReaderWriterLockSlim = New ReaderWriterLockSlim()

    Public Sub DoSomethingWithReaderWriteLockSlim()
        lockObj.EnterReadLock() ' Compliant: the lock will be released in the finally block

        Try
            If IsInitialized() Then
                ' ...
            End If
        Finally
            lockObj.ExitReadLock()
        End Try
    End Sub
End Class

Resources

   Synchronization of access to a shared resource 
   CWE - CWE-459 - Incomplete Cleanup 
   SyncLock
  statement 
   Finally block