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c#inheritancedictionaryienumerableencapsulation

How do I correctly wrap a Dictionary<T,U> and expose an enumerator?


I am encapsulating a Dictionary in my object. How do I expose IEnumerable>?

Before

class HashRunningTotalDB : Dictionary<int, SummaryEntity>
{
         /... 
} 

// WORKS!
static void Main ()
{
       HashRunningTotalDB  tempDB = new HashRunningTotalDB();
       //todo: load temp DB

       foreach(var item in tempDB)
       {
           Console.Writeline(item.Key + " " + item.Value.SomeProperty);
       }
}

After

class HashRunningTotalDB : IEnumerable
{
    Dictionary<int, SummaryEntity> thisHashRunningTotalDB = new Dictionary<int, SummaryEntity>();

      //QUESTION:  HOW DO I IMPLEMENT THE GENERIC ENUMERATOR HERE?
    // The following doesn't behave the same as the previous implementation
     IEnumerator IEnumerable.GetEnumerator()
    {
        return thisHashRunningTotalDB.GetEnumerator();
    }


    // The following doesn't compile
     Dictionary<int, SummaryEntity>.Enumerator IEnumerable<Dictionary<int, SummaryEntity>>.GetEnumerator()
    {
        return thisHashRunningTotalDB.GetEnumerator();
    }
} 



static void Main ()
{
       HashRunningTotalDB  tempDB = new HashRunningTotalDB();
       //todo: load temp DB


       // NOT WORKING
       foreach(var item in tempDB)
       {
           Console.Writeline(item.Key + " " + item.Value.SomeProperty);
       }
}

Solution

  • Implement IEnumerable<KeyValuePair<int, SummaryEntity>>

    class HashRunningTotalDB : IEnumerable<KeyValuePair<int, SummaryEntity>>
    {
       Dictionary<int, SummaryEntity> thisHashRunningTotalDB =
          new Dictionary<int, SummaryEntity>();
    
       public IEnumerator<KeyValuePair<int, SummaryEntity>> GetEnumerator()
       {
          return thisHashRunningTotalDB.GetEnumerator();
       }
    
       IEnumerator IEnumerable.GetEnumerator()
       {
          return GetEnumerator();
       }
    }
    
    static void Main()
    {
       HashRunningTotalDB tempDB = new HashRunningTotalDB();
    
       // should work now
       foreach(KeyValuePair<int, SummaryEntity> item in tempDB)
       {
           Console.Writeline(item.Key + " " + item.Value.SomeProperty);
       }
    }