C# Will the typical IDisposable pattern not cause resource leak in some condition

Question

Below is a typical IDisposable implementation for C# class which has managed and unmanaged resources both. My question is, Can there be a situation where ~DisposableObject() destructor method gets called before the Dispose() method of the class for any given object. And if that is possible, will it not set the flag disposed to false, and the managed resources will never get a chance to be disposed off because Dispose(bool) method does not do anything if disposed flag is set to false.

public class DisposableObject : IDisposable
    {
        private bool disposed;
        private ManagedResource mgdRs;
        private UnmanagedResource unMgdRs;

        public DisposableObject()
        {
            mgdRs = new ManagedResource();
            unMgdRs = new UnmanagedResource();
        }

        ~DisposableObject()
        {
            this.Dispose(false);
        }
    
        public void Dispose()
        {    
             this.Dispose(true);
             GC.SuppressFinalize(this);       
        }

        protected virtual void Dispose(bool disposing)
        {
            if (!this.disposed)
            {
                if (disposing)
                {
                    // clean up managed resources
                    //call dispose on your member objects
                    mgdRs.Dispose();
                }

                // clean up unmanaged resources
                unMgdRs.Destroy();
                this.disposed = true;
            }
        }
    }
}

Answer 1

Yes, it is possible for the finalizer to be called first. However, there are three things to understand here.

First, it's very rare in C# to need to implement the full IDisposable pattern. The full pattern is only needed when you have both managed and original unmanaged resources in the same type.

Most unmanaged resources you deal with already have a managed wrapper you rely on instead, and therefore there is no need to implement another finalizer/destructor. Additionally, developers implementing an original unmanaged resource requiring a finalizer will often limit themselves to just that one resource, such that there are no managed resources in the same type to create the conflict from the question. In this way, the unmanaged resource becomes managed, and now can be included as part of a simpler pattern.

The second thing to understand is the finalizer runs as part of garbage collection. Given the finalizer is running, we know the unmanaged resources are cleaned up, and only managed resources remain. The very definition of a managed resource is something that the garbage collector will take of. Therefore, if the finalizer runs too soon, causing the Dispose() call to miss the managed resources, that's okay, because the garbage collector is already running and will take care of it.

This brings me to my third thing. Not only may the finalizer be called first, but when that happens its very likely the finalizer is called only, because it would be highly unusual for anything but the garbage collector to invoke the finalizer. If the garbage collector is running for an object, there won't be any reference remaining which might be used to also call Dispose(), whether intentionally or implicitly. And again, that's okay: the finalizer is running, so we know unmanaged resources will be cleaned up, and the garbage collector is running, so we know managed resources will also be cleaned up.