AddOrUpdate method for IDictionary since none exists for some reason

DictionaryExtension.cs

void Main()
{
	Dictionary<int, int> dict = new Dictionary<int, int>();
	Random rndm = new Random();
	for(int i = 0; i < 100; i++)
	{
		int foo = rndm.Next(10);
		dict.AddOrUpdate(foo, 1, (val) => { return val+=1; });
	}
	
	foreach(var key in dict.Keys)
	{
		Console.WriteLine("{0} = {1}", key, dict[key]);
	}
}


public static class Extensions
{
   public static void AddOrUpdate<TKey, TValue>(this IDictionary<TKey, TValue> dict, TKey key, Func<TKey, TValue> defaultValue,  Func<TValue, TValue> updateOperation)
   {
       if(dict.ContainsKey(key))
	   {
	   	dict[key] = updateOperation(dict[key]);
	   } else {
	   	dict.Add(key, defaultValue(key));
	   }
   }
   public static void AddOrUpdate<TKey, TValue>(this IDictionary<TKey, TValue> dict, TKey key, TValue defaultValue,  Func<TValue, TValue> updateOperation)
   {
   		dict.AddOrUpdate(key, (k) => { return defaultValue; }, updateOperation);
   }
}