C#中Dispose和Close的区别

using System; 
namespace ConsoleApplication
{
abstract class MyStream : IDisposable
{
public MyStream()
{
m_unmanagedResource = Marshal.AllocCoTaskMem(100);
m_bitmap = new Bitmap(50, 50);
}

#region IDisposable Members
void IDisposable.Dispose()
{
Dispose(true);
GC.SuppressFinalize(this);
}

protected virtual void Dispose(bool isDisposing)
{
if (!m_disposed)
{
if (isDisposing)
{
m_bitmap.Dispose();
}
Marshal.FreeCoTaskMem(m_unmanagedResource);
m_disposed = true;
}
}

public void Close()
{
((IDisposable)this).Dispose();
}

~MyStream()
{
Dispose(false);            
}

private IntPtr m_unmanagedResource;     // Unmanaged resource
private Bitmap m_bitmap;                // IDisposable managed resources
private bool m_disposed;

#endregion
}

class MyDerivedStream : MyStream
{
public MyDerivedStream()
{
m_anotherMemory = Marshal.AllocCoTaskMem(20);
m_anotherImage = new Bitmap(24, 24);
}

protected override void Dispose(bool isDisposing)
{
if (!m_disposed)
{
if (isDisposing)
{
m_anotherImage.Dispose();
}

Marshal.FreeCoTaskMem(m_anotherMemory);
base.Dispose(isDisposing);
m_disposed = true;
}
}

public static void Main(string[] args)
{
MyStream aStream = new MyDerivedStream();

aStream.Close();          // Allowed
// aStream.Dispose();    // Cannot compile

((IDisposable)aStream).Dispose();     // Allowed

//
//  This one works as well, because newStream calls 
the explicit implemented
//  IDisposable.Dispose method
//
using (MyStream newStream = new MyDerivedStream())
{
//
//  Do something
//
}
}

private IntPtr m_anotherMemory;
private Bitmap m_anotherImage;
private bool m_disposed;
}
}