Question

i have this ObservableCollection<MyData> list that i want to insert inside my Singleton:

public sealed class Singleton
{
   private static volatile Singleton instance;
   private static object syncRoot = new Object();
   public static ObservableCollection<MyData> list {get; set;}

   private Singleton() {}

   public static Singleton Instance
   {
      get 
      {
         if (instance == null) 
         {
            lock (syncRoot) 
            {
               if (instance == null)
               {
                  instance = new Singleton();
                  list = new ObservableCollection<MyData>();
               }
            }
         }

         return instance;
      }
   }
}

Is this the This is the right way to define it ?

Answer 1

I don't think it is. If the ObservableCollection should be a member of the Singleton class, instantiate it in the Singleton's private constructor. If it shouldn't, I don't see why you doing it this way. What happens when you call Singleton.list BEFORE Singleton.Instance? NullReferenceException. And since its setter is public, it can be set from outside as well which is probably not what you want.

I would modify your code like this:

public sealed class Singleton
{
   private static volatile Singleton instance;
   private static object syncRoot = new Object();

   public ObservableCollection<MyData> list {get; private set;}

   private Singleton() {
       list = new ObservableCollection<MyData>();
   }

   public static Singleton Instance
   {
      get 
      {
         if (instance == null) 
         {
            lock (syncRoot) 
            {
               if (instance == null)
               {
                  instance = new Singleton();
               }
            }
         }

         return instance;
      }
   }
}

Singleton with ObservableCollection as a member

1 个答案: