Disposing base class before inherited class

Question

I have two classes:

public abstract class UnitOfWorkBase: IDisposable { }
public sealed class UnitOfWorkSql: UnitOfWorkBase { }

The Dispose method of the derived class normally looks like this:

protected override void Dispose (bool disposing)
{
    if (!this.Disposed)
    {
        if (disposing)
        {
            // Managed.
        }

        // Unmanaged.

        this.Disposed = true;
    }

    base.Dispose(disposing);
}

I've always seen the call to base.Dispose(disposing) at the end of the method. However, in a recent scenario, there is a need to dispose objects of the base class before objects in the derived class as follows:

protected override void Dispose (bool disposing)
{
    base.Dispose(disposing);

    if (!this.Disposed)
    {
        if (disposing)
        {
            // Managed.
        }

        // Unmanaged.

        this.Disposed = true;
    }
}

I'm not sure if this is considered bad practice. Is there anything to watch out for?

Answer 1

I think you should break the usual pattern here. Instead of:

class BaseClass
{
    protected virtual void Dispose(bool disposing)
    {
        if (disposing)
        {
            //dispose my resources
        }
    }
}

Write something like:

class BaseClass
{
    private void Dispose(bool disposing)
    {
        if (disposing)
        {
            //dispose my resources
            DisposeManagedOverride();
        }

        CloseUnmanagedOverride();
    }

    protected virtual void DisposeManagedOverride() {}

    protected virtual void CloseUnmanagedOverride() {}
}

This way you will ensure the proper order of the resources release.