CA2216: Disposable types should declare finalizer

Cause

A type that implements System.IDisposable, and has fields that suggest the use of unmanaged resources, does not implement a finalizer as described by System.Object.Finalize.

Rule description

A violation of this rule is reported if the disposable type contains fields of the following types:

• System.IntPtr

• System.UIntPtr

• System.Runtime.InteropServices.HandleRef

How to fix violations

To fix a violation of this rule, implement a finalizer that calls your Dispose method.

When to suppress warnings

It is safe to suppress a warning from this rule if the type does not implement IDisposable for the purpose of releasing unmanaged resources.

Suppress a warning

If you just want to suppress a single violation, add preprocessor directives to your source file to disable and then re-enable the rule.

#pragma warning disable CA2216
// The code that's violating the rule is on this line.
#pragma warning restore CA2216

To disable the rule for a file, folder, or project, set its severity to none in the configuration file.

[*.{cs,vb}]
dotnet_diagnostic.CA2216.severity = none

For more information, see How to suppress code analysis warnings.

Example

The following example shows a type that violates this rule.

public class DisposeMissingFinalize : IDisposable
{
 private bool disposed = false;
 private IntPtr unmanagedResource;

 [DllImport("native.dll")]
 private static extern IntPtr AllocateUnmanagedResource();

 [DllImport("native.dll")]
 private static extern void FreeUnmanagedResource(IntPtr p);

 DisposeMissingFinalize()
 {
 unmanagedResource = AllocateUnmanagedResource();
 }

 protected virtual void Dispose(bool disposing)
 {
 if (!disposed)
 {
 // Dispose of resources held by this instance.
 FreeUnmanagedResource(unmanagedResource);
 disposed = true;

 // Suppress finalization of this disposed instance.
 if (disposing)
 {
 GC.SuppressFinalize(this);
 }
 }
 }

 public void Dispose()
 {
 Dispose(true);
 }

 // Disposable types with unmanaged resources implement a finalizer.
 // Uncomment the following code to satisfy rule:
 // DisposableTypesShouldDeclareFinalizer
 // ~TypeA()
 // {
 // Dispose(false);
 // }
}

Related rules

CA1816: Call GC.SuppressFinalize correctly

See also

• System.IDisposable
• System.IntPtr
• System.Runtime.InteropServices.HandleRef
• System.UIntPtr
• System.Object.Finalize
• Dispose Pattern