IDISP023.md

IDISP023

Don't use reference types in finalizer context

Topic	Value
Id	IDISP023
Severity	Warning
Enabled	True
Category	IDisposableAnalyzers.Correctness
Code	DisposeMethodAnalyzer
	FinalizerAnalyzer

Description

Don't use reference types in finalizer context.

Motivation

Any use of reference types from a finalizer is hazardous. When that finalizer was invoked as part of AppDomain shutdown, the CLR makes no guarantee regarding order of finalization or GC for a typical finalizer, and thus any access to a reference type (other than strictly this) could access violation and crash the process. The only safe activity from a finalizer is accessing value types and calling p/invoke methods, which limits safe activity to calling into native code to release resources. Even accessing SafeHandles is unsafe, which is why these types have their own finalizers rather than relying on their owners to dispose of them during finalization.

How to fix violations

Invalid:

protected virtual void Dispose(bool disposing)
{
   if (disposing)
   {
   }

   this.logger.Log("In Dispose(bool)"); // violation! ILogger is a ref type and we're not inside the above block
}

Valid:

protected virtual void Dispose(bool disposing)
{
   if (disposing)
   {
       this.logger.Log("In Dispose(bool)");
   }
}

Configure severity

Via ruleset file.

Configure the severity per project, for more info see MSDN.

Via #pragma directive.

#pragma warning disable IDISP023 // Don't use reference types in finalizer context
Code violating the rule here
#pragma warning restore IDISP023 // Don't use reference types in finalizer context

Or put this at the top of the file to disable all instances.

#pragma warning disable IDISP023 // Don't use reference types in finalizer context

Via attribute [SuppressMessage].

[System.Diagnostics.CodeAnalysis.SuppressMessage("IDisposableAnalyzers.Correctness", 
    "IDISP023:Don't use reference types in finalizer context", 
    Justification = "Reason...")]