>>>>>>Using a Dictionary < Tkey, TValue > would be better
>>>>>
>>>>>Thanks, I remember having read some of that in previous threads. I might have to consider that.
>>>>
>>>>
>>>>You can update the value of a dictionary
>>>>
>>>>Here, I use a Tuple of three integers - for simplicity the first one is the key
>>>>
>>>>
>>>>

>>>>		public static void Main()
>>>>		{
>>>>
>>>>
>>>>			Dictionary<int, Tuple<int, int, int>> dict = new Dictionary<int, Tuple<int, int, int>>();
>>>>
>>>>			Tuple<int, int, int> t;  // key is tuple.Item1
>>>>
>>>>			t = new Tuple<int, int, int>(1, 1, 1);
>>>>			UpdateDictionary(dict, t);
>>>>
>>>>			t = new Tuple<int, int, int>(2, 1, 1);
>>>>			UpdateDictionary(dict, t);
>>>>
>>>>			PrintDictionary("Before any update", dict);
>>>>
>>>>			t = new Tuple<int, int, int>(2, 2, 2);
>>>>			UpdateDictionary(dict, t);
>>>>
>>>>			PrintDictionary("After update", dict);
>>>>			Console.ReadLine();
>>>>		}
>>>>		static void UpdateDictionary(Dictionary<int, Tuple<int, int, int>> dict, Tuple<int, int, int> t)
>>>>		{
>>>>			if (dict.ContainsKey(t.Item1) )
>>>>			{
>>>>				dict[t.Item1] = t;
>>>>			}
>>>>			else
>>>>				dict.Add(t.Item1, t);
>>>>		}
>>>>		static void PrintDictionary(string msg, Dictionary<int, Tuple<int, int, int>> dict)
>>>>		{
>>>>			Console.WriteLine(msg);
>>>>			foreach (KeyValuePair<int, Tuple<int, int, int>> x in dict)
>>>>			{
>>>>				Console.WriteLine("{0} {1} {2}", x.Value.Item1, x.Value.Item2, x.Value.Item3);
>>>>			}
>>>>
>>>>		}
>>>>

Since the key is in the data I'd consider using KeyedCollection instead of Dictionary ?
>>>UPDATE : Assuming the key is an int.....
>>
>>Well - I made the key part of the data for simplicity - it doesn't need to be
>>
>>If you go for a KeyedCollection, wouldn't you need to subclass KeyedCollection first (and implement GetKeyForItem() ? http://msdn.microsoft.com/en-us/library/ms132454.aspx)
>
>Yes. Maybe not worth the candle but would be simpler when adding items etc......


Candle or no candle

I had not heard about KeyedCollection before and I am glad you brought it up - may be useful with the link Rob posted

Adding the key to the data is something I do in vfp (washing out my mouth with soap) so that the key is available in the foreach loop