Hashtable with multiple values for single key

Question

I want to store multiple values in single key like:

HashTable obj = new HashTable();
obj.Add(\"1\", \"test\");
obj.Add(\"1\", \"Test1\");

Right

Answer 1

I'm using my own MultiDictionary class. It's based on a Dictionary> but offers a bit of syntax sugar on top of that. Should be easy to extent Entry to implement IList

public class MultiDictionary
{
    private Dictionary> data = new Dictionary>();

    public struct Entry : IEnumerable
    {
        private readonly MultiDictionary mDictionary;
        private readonly TKey mKey;

        public TKey Key { get { return mKey; } }

        public bool IsEmpty
        {
            get
            {
                return !mDictionary.data.ContainsKey(Key);
            }
        }

        public void Add(TValue value)
        {
            List list;
            if (!mDictionary.data.TryGetValue(Key, out list))
                list = new List();
            list.Add(value);
            mDictionary.data[Key] = list;
        }

        public bool Remove(TValue value)
        {
            List list;
            if (!mDictionary.data.TryGetValue(Key, out list))
                return false;
            bool result = list.Remove(value);
            if (list.Count == 0)
                mDictionary.data.Remove(Key);
            return result;
        }

        public void Clear()
        {
            mDictionary.data.Remove(Key);
        }

        internal Entry(MultiDictionary dictionary, TKey key)
        {
            mDictionary = dictionary;
            mKey = key;
        }

        public IEnumerator GetEnumerator()
        {
            List list;
            if (!mDictionary.data.TryGetValue(Key, out list))
                return Enumerable.Empty().GetEnumerator();
            else
                return list.GetEnumerator();
        }
        System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
        {
            return GetEnumerator();
        }
    }

    public Entry this[TKey key]
    {
        get
        {
            return new Entry(this, key);
        }
    }
}