Use of Finalize/Dispose method in C#

C# 2008

I have been working on this for a while now, and I am still confused about the use of finalize and dispose methods in code. My questions are below:

1. I know that we only need a finalizer while disposing unmanaged resources. However, if there are managed resources that make calls to unmanaged resources, would it still need to implement a finalizer?

2. However, if I develop a class that doesn’t use any unmanaged resource – directly or indirectly, should I implement the IDisposable to allow the clients of that class to use the ‘using statement’?

   Would it be feasible to implement IDisposable just to enable clients of your class to use the using statement?

   using(myClass objClass = new myClass())
   {
       // Do stuff here
   }
   

3. I have developed this simple code below to demonstrate the Finalize/dispose use:

   public class NoGateway : IDisposable
   {
       private WebClient wc = null;
   
       public NoGateway()
       {
           wc = new WebClient();
           wc.DownloadStringCompleted += wc_DownloadStringCompleted;
       }
   
   
       // Start the Async call to find if NoGateway is true or false
       public void NoGatewayStatus()
       {
           // Start the Async's download
               // Do other work here
           wc.DownloadStringAsync(new Uri(www.xxxx.xxx));
       }
   
       private void wc_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e)
       {
           // Do work here
       }
   
       // Dispose of the NoGateway object
       public void Dispose()
       {
           wc.DownloadStringCompleted -= wc_DownloadStringCompleted;
           wc.Dispose();
           GC.SuppressFinalize(this);
       }
   }
   

Question about the source code:

1. Here I have not added the finalizer, and normally the finalizer will be called by the GC, and the finalizer will call the Dispose. As I don’t have the finalizer, when do I call the Dispose method? Is it the client of the class that has to call it?

   So my class in the example is called NoGateway and the client could use and dispose of the class like this:

   using(NoGateway objNoGateway = new NoGateway())
   {
       // Do stuff here   
   }
   

   Would the Dispose method be automatically called when execution reaches the end of the using block, or does the client have to manually call the dispose method? i.e.

   NoGateway objNoGateway = new NoGateway();
   // Do stuff with object
   objNoGateway.Dispose(); // finished with it
   

2. I am using the WebClient class in my NoGateway class. Because WebClient implements the IDisposable interface, does this mean that WebClient indirectly uses unmanaged resources? Is there a hard and fast rule to follow this? How do I know that a class uses unmanaged resources?