How to model this as a LINQ query?

Question

I have the following classes:

public class A
{
    public string P1 {get;set;}
    public string P2 {get;set;}
    public string P3 {get;set;}
    public string P3 {get;set;}
}

public class Id
{
    public string Main {get;set;}
    public string SubMain {get;set;}
}

Having a List I need to return a List with all the pairs P1 - P2 that are different in the List.

So if in the list I have:

 P1 = "A" - P2 "B"
 P1 = "A" - P2 "C"
 P1 = "B" - P2 "B"
 P1 = "A" - P2 "B"

I need to return a List with 3 Id like:

 Main = "A" - SubMain "B"
 Main = "A" - SubMain "C"
 Main = "B" - SubMain "B"

Is this possible with just one LINQ query? I would say yes but I'm not very comfortable with the Select statement.

Thanks in advance.

Answer 1

You can use the Tuple class, it will do all the work on the distincts for you :

myList.Select(a => Tuple.Create(a.P1, a.P2))
      .Distinct()
      .Select(tuple => new Id() { Main = tuple.Item1, SubMain = tuple.Item2 } )
      .ToList();

The advantage is that Tuple class already override members like Equals, GetHashCode, all you need for performing a Distinct on a collection.