Question

I am looking for a solution that lets me store and lookup multiple tuples. Dictionary only provides a simple way to lookup keys but not the values. I understand why (non-uniqueness possibility of values). However, what if each and every entry (keys and values) are strictly unique. Is there a collection that easily lets me store and lookup whatever key I chose and returns the matching field of such key? When looking up values I would necessarily have to specify the key field and the desired lookup field. I target C# 4.0

Example:

Collection<string, int, myEnum> myCollection = new ...

myCollection.Add("abc", 5, myEnum.First);
myCollection.Add("def", 6, myEnum.Second);

myCollection[int, myEnum, 6] = Second (of type myEnum) -> I just made up the way how a key and value field could be specified. Does such collection exist or would I need to roll my own?

I understand I am getting into the concept of tables but would like to avoid using a table structure if at all possible.

Note: The number of tuples will be limited to <20 (so if I rolled my own I would not be overly concerned with having to loop but I look for something more elegant)

Thanks

Answer 1

You can just a hashset with a tuple. Like this:

var hs=new HashSet<Tuple<string,int,myEnum>>();

then to add you do this (the add function is O(1)):

hs.Add(new Tuple<string,int,myEnum>("abc", 5, myEnum.First));
hs.Add(new Tuple<string,int,myEnum>("def", 6, myEnum.Second));

to look up the tuple you do this (the contains function is O(1)):

var tupleTolookUp=new Tuple<string,int,myEnum>("abc", 5, myEnum.First);
if(hs.Contains(tupleTolookUp))
{
    //do what ever with the tupleTolookUp
}

In the hashset the Tuples has to be unique. But the good thing is that you do not have to override the Equals and gethashcode. Because the tuple does that internal.

References:

• HashSet Class
• Tuple Class