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Disposable types should declare finalizer

TypeName

DisposableTypesShouldDeclareFinalizer

CheckId

CA2216

Category

Microsoft.Usage

Breaking Change

Non Breaking

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

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

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

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

The following example shows a type that violates this rule.

using System;  
using System.Runtime.InteropServices;

namespace UsageLibrary
{
    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); 
        // }
    }
}

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