gistfile1.cs

	public static class DictionaryExtensions
	{
		public static TValue GetOrAdd<TKey, TValue>(
			this IDictionary<TKey, TValue> dictionary, TKey key, Func<TValue> create)
		{
			TValue result;
			if(!dictionary.TryGetValue(key, out result))
			{
				result = create();
				dictionary[key] = result;
			}
			return result;
		}
	}