using(NoGateway objNoGateway = new NoGateway())

等于

try
{
    NoGateway = new NoGateway();
}

finally
{
    NoGateway.Dispose();
}

在GC销毁对象时调用终结器。这可能与你离开方法时完全不同。Dispose of IDisposable在你离开using块后立即被调用。因此，这种模式通常是在您不再需要资源后立即使用using来释放它们。

using(NoGateway objNoGateway = new NoGateway())

等于

try
{
    NoGateway = new NoGateway();
}

finally
{
    NoGateway.Dispose();
}

在GC销毁对象时调用终结器。这可能与你离开方法时完全不同。Dispose of IDisposable在你离开using块后立即被调用。因此，这种模式通常是在您不再需要资源后立即使用using来释放它们。

1) WebClient是一个托管类型，所以你不需要终结器。如果您的用户不Dispose()您的NoGateway类，并且本机类型(不被GC收集)之后需要清理，则需要结束器。在这种情况下，如果用户没有调用Dispose()，所包含的WebClient将在NoGateway调用之后被GC丢弃。

间接地，是的，但你不必担心。你的代码是正确的，你不能防止你的用户很容易忘记Dispose()。

使用lambdas代替IDisposable。

我从来没有对使用/IDisposable这个想法感到兴奋。问题是它要求调用者:

知道他们必须使用IDisposable 记住使用“using”。

我新的首选方法是使用工厂方法和lambda代替

假设我想用SqlConnection(应该用using包装的东西)做一些事情。通常你会这么做

using (Var conn = Factory.MakeConnection())
{
     conn.Query(....);
}

新方法

Factory.DoWithConnection((conn)=>
{
    conn.Query(...);
}

在第一种情况下，调用者不能简单地使用using语法。在第二种情况下，用户没有选择。没有创建SqlConnection对象的方法，调用者必须调用DoWithConnection。

DoWithConnection看起来像这样

void DoWithConnection(Action<SqlConnection> action)
{
   using (var conn = MakeConnection())
   {
       action(conn);
   }
}

MakeConnection现在是私有的

If you are using other managed objects that are using unmanaged resources, it is not your responsibility to ensure those are finalized. Your responsibility is to call Dispose on those objects when Dispose is called on your object, and it stops there. If your class doesn't use any scarce resources, I fail to see why you would make your class implement IDisposable. You should only do so if you're: Know you will have scarce resources in your objects soon, just not now (and I mean that as in "we're still developing, it will be here before we're done", not as in "I think we'll need this") Using scarce resources Yes, the code that uses your code must call the Dispose method of your object. And yes, the code that uses your object can use using as you've shown. (2 again?) It is likely that the WebClient uses either unmanaged resources, or other managed resources that implement IDisposable. The exact reason, however, is not important. What is important is that it implements IDisposable, and so it falls on you to act upon that knowledge by disposing of the object when you're done with it, even if it turns out WebClient uses no other resources at all.

来自msdn的模式

public class BaseResource: IDisposable
{
   private IntPtr handle;
   private Component Components;
   private bool disposed = false;
   public BaseResource()
   {
   }
   public void Dispose()
   {
      Dispose(true);      
      GC.SuppressFinalize(this);
   }
   protected virtual void Dispose(bool disposing)
   {
      if(!this.disposed)
      {        
         if(disposing)
         {
            Components.Dispose();
         }         
         CloseHandle(handle);
         handle = IntPtr.Zero;
       }
      disposed = true;         
   }
   ~BaseResource()      
   {      Dispose(false);
   }
   public void DoSomething()
   {
      if(this.disposed)
      {
         throw new ObjectDisposedException();
      }
   }
}
public class MyResourceWrapper: BaseResource
{
   private ManagedResource addedManaged;
   private NativeResource addedNative;
   private bool disposed = false;
   public MyResourceWrapper()
   {
   }
   protected override void Dispose(bool disposing)
   {
      if(!this.disposed)
      {
         try
         {
            if(disposing)
            {             
               addedManaged.Dispose();         
            }
            CloseHandle(addedNative);
            this.disposed = true;
         }
         finally
         {
            base.Dispose(disposing);
         }
      }
   }
}