Create a List of pairs in .net

Question

I need to create a List<> of pairs of my classes. such as: List<Class1, Class2>

How would you do it? I can not use the "Pair" datatype because it's in system.web.UI.

Would you create a list of arrays? Create a struct of both classes and add them to a list?

Is there another way I don't know of and I'm just a noob?

Note: I don't want the list to auto-sort in any way.

Answer 1

You could create your own Pair class ...

Answer 2

I just use this:

var list = List<KeyValuePair<String, String>>;

or any other data type of course. It means you are accessing it like list(0).Key and list(0).Value but this doesn't bother me unless I am exposing the list externally.

Answer 3

It's designed to be used in Dictionaries, but you could use a KeyValuePair

Answer 4

Can you use a generic Dictiontary instead of a generic list?

Answer 5

You could simply use a Dictionary<>

Answer 6

As Hans Kesting points out, you could create your own Pair class, but often such a construct tends to cover up the fact that the relationship between the two types you are trying to pair actually represent a stronger concept in your API.

So instead of ending up with a generic Pair (or Tuple) your code may be more readable if you explicitly type the pair as a strong concept with good naming.

Answer 7

I know some people get uncomfortable about this - see a discussion here - but there's nothing to stop you referencing System.Web in a non-web project, and then you can use System.Web.UI.Pair quite happily.

Answer 8

Simply create your own pair class:

class Pair<TFirst, TSecond> {

  public TFirst First { get; set; }

  public TSecond Second { get; set; }

}

Initialize it like this:

Pair<String, String> pair = new Pair<String, String> {
  First = "first",
  Second = "second"
};

The next release of .NET (4.0) has tuples which is a more general solution to the problem.

Answer 9

I would go with either KeyValuePair (as used by Dictionary) or create my own struct that acts as a typed container, emphasising the relation between the types.

By the time I've typed this several people have posted much the same - but I'll post this anyway for reassurance :-)

Answer 10

One answer to everybody (It's the same answer and I don't want to add comments for everyone...):

I feel like using Key-Value combinations (or dictionary) is not natural because it's not representing a key and a value.

I'm trying to avoid creating my own class to represent the pair.

Maybe I'll import the System.Web.UI... feels crappy about it though

Answer 11

I agree with using a dictionary unles you can have mulitple values that are the same as dictionaries require unique Key values.

If you really needed pairs, you could make a class to do it and use it like this:

List<Pair<string, int>> pairs = new List<Pair<string, int>>();
pairs.Add(new Pair<string, int>("entry1", 1));
pairs.Add(new Pair<string, int>("entry2", 2));

Class

public class Pair<T, T2>
{
    T Value1;
    T2 Value2;
     public Pair(T value1, T2 value2)
     {
         Value1 = value1;
         Value2 = value2;
     }
}

I used generics because you didn't specify what type (this will work with any 2 Types). you could simplify it even more if you hard-coded the types.

Answer 12

Surely anonymous types are suited perfectly for this:

var Pair = new { Part1 = "A", Part2 = 6 };
var PairList = (new[] { Pair }).ToList();
PairList.Add(new { Part1  = "B", Part2  = 9 });

...

List[0].Part1 = "C";

Basically this is making a new "var object" containing a string and an int. Adding it to an array and invoking the ToList() extension method provided by System.Linq on the array to return an object which is effectively List<"typeof(Pair)"> object.

(EDIT)

Or neater still:

var PairList2 = (new[] { new { Part1 = "A", Part2 = 6 } }).ToList();

(ideas pinched from: http://kirillosenkov.blogspot.com/2008/01/how-to-create-generic-list-of-anonymous.html)