public static ImmutableDictionary <T1, ImmutableList <T2> > AddToListOfValues <T1, T2>(this ImmutableDictionary <T1, ImmutableList <T2> > dictionary, T1 key, T2 item)
{
return(dictionary.SetItem(key, dictionary.GetOrEmpty(key).Add(item)));
}
public static ImmutableDictionary <T1, ImmutableList <T2> > AddNtoM <T1, T2>(this ImmutableDictionary <T1, ImmutableList <T2> > mapping1, ICollection <T1> items1, ICollection <T2> items2)
{
return(mapping1.SetItems(
items1.SelectMany(
item1 =>
{
return items2.Select(item2 => new KeyValuePair <T1, ImmutableList <T2> >(item1, mapping1.GetOrEmpty(item1).Add(item2)));
})));
}