C# Dictionary with two Values per Key?

Question

I have a situation in code where a Dictionary<string, string> seemed like the best idea - I need a collection of these objects and I need them to be accessible via a unique key. Exactly what the Dictionary concept is for, right?

Well, the requirements have expanded to the point where I now need to hold an additional bit of information per-key (a boolean value, if you're curious).

So, I figure expand the concept to create a new data structure with the string and the boolean and have it now be a Dictionary<string, NewCustomObject>.

However, for just one additional value like a boolean flag, it just feels like overkill. And yet I don't know of any Dictionary-like generic object with two values per key.

Is just having a Dictionary of custom objects the best way to go about this or is there something simpler for this scenario?

Answer 1

Doesn't this work for ya?

Dictionary<string, List<string>>

Or you could use a Tuple and have a dictionary of that:

Dictionary<string, Tuple<string, bool>>

Answer 2

I don't believe .net has Multi-Map built in which is generally a data-structure you can use to do this type of storage. On the other hand I don't think it's overkill at all just using a custom object that holds both a string and a boolean.

Answer 3

The Multivalue dictionary post might serve your needs.

Answer 4

I think generally you're getting into the concept of Tuples - something like Tuple<x, y, z>, or Tuple<string, bool, value>.

C# 4.0 will have dynamic support for tuples, but other than that, you need to roll your own or download a Tuple library.

You can see my answer here where I put some sample code for a generic tuple class. Or I can just repost it here:

public class Tuple<T, T2, T3>
{
    public Tuple(T first, T2 second, T3 third)

    {
        First = first;
        Second = second;
        Third = third;
    }

    public T First { get; set; }
    public T2 Second { get; set; }
    public T3 Third { get; set; }

}

Answer 5

Actually, what you've just described is an ideal use for the Dictionary collection. It's supposed to contain key:value pairs, regardless of the type of value. By making the value its own class, you'll be able to extend it easily in the future, should the need arise.

Answer 6

A Dictionary is just a keyed collection of objects. As such, it will hold any type of object you want. Even the simplest of objects, like, say, an array (which derives from Object), but requires a lot less code on your behalf.

Rather than writing an entire class, stuff a dynamically allocated array, or a List in the value and run with that.

Dictionaries are highly flexible that way.

Answer 7

What about Lookup class?

Edit:

After read the question carefully think this is not the best solution, but it still a good one for the dictionary with some values per a single key.

Answer 8

class MappedValue
{
    public string SomeString { get; set; }
    public bool SomeBool { get; set; }
}

Dictionary<string, MappedValue> myList = new Dictionary<string, MappedValue>;

Answer 9

Another idea is to store the boolean in a separate data structure, e.g. a HashSet.

Answer 10

Tuple is always a good solution. Furthermore in an object oriented approach, always favour composition over inheritance. Construct a composite object doing the grouping. Simply. I think you are covered with some nice and clean solutions here, from fellow stackoverflow'ers. :)