//单一类的实现
class MyClass : IDisposable 
{
  public MyClass(){} 
  ~MyClass() 
  { 
   // In case the client forgets to call 
   // Dispose , destructor will be invoked for 
   Dispose(false); 
  } 
  protected virtual void Dispose(bool disposing) 
  { 
   if (disposing) 
   { 
    // Free managed objects. 
   } 
   // Free unmanaged objects 
  } 
  public void Dispose() 
  { 
   Dispose(true); 
   // Ensure that the destructor is not called 
   GC.SuppressFinalize(this); 
  } 
}