How Safe is the Using Block?

File2.cs

var proxy = new MyProxy();
try
{
    // Do some work.
    proxy.Close();
}
catch( CommunicationException ex )
{
    proxy.Abort();
}
catch( TimeoutException ex )
{
    proxy.Abort();
}
catch( Exception ex )
{
    proxy.Abort();
    throw;
}

File3.cs

public abstract class ProxyBase<TChannel> : ClientBase<TChannel>, IDisposable where TChannel : class
{
	protected void CheckDisposed()
	{
		if( disposed )
		{
			throw new ObjectDisposedException( GetType().Name );
		}
	}

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

	protected virtual void Dispose( bool disposing )
	{
		if( !disposed )
		{
			if( disposing )
			{
				try
				{
					base.Close();
				}
				catch( CommunicationException ex )
				{
					base.Abort();
				}
				catch( TimeoutException ex )
				{
					base.Abort();
				}
				catch( Exception ex )
				{
					base.Abort();
					throw;
				}
			}

			disposed = true;
		}
	}
}

File5.cs

using( var proxy = new MyProxy() )
{
    // Do some work.
}