using System;

using System.Collections.Generic;

using System.Linq;

​

public class MyNode

{

    public int Id

    {

        get;

        set;

    }

​

    public string Name

    {

        get;

        set;

    }

​

    public int Age

    {

        get;

        set;

    }

    public override string ToString() {

        return Id + ": " + Name + " - " + Age;

    }

}

​

public delegate object Func2<in T>(T arg);

public class Program

{

    public static void Main()

    {

        // The selector is always a bool

        Func<MyNode, bool> isChild = x => x.Age < 18;

        Func<MyNode, bool> isAdult = x => x.Age >= 18;

        // So it's always ok to use

        Func<MyNode, bool> isAgeOk = isAdult;

        // The sort field can be different type (int, string, ...)

        Func<MyNode, IComparable> sortByName = x => x.Name;

        Func<MyNode, IComparable> sortByAge = x => x.Age;

        Func<MyNode, IComparable> sortById = x => x.Id;

        var currentSort = sortByAge;

        // With this declaration, i can't use : Func<MyNode, int> currentSort = sortByName

        var LstNodes = new List<MyNode>()

        {new MyNode()

        {Id = 1, Name = "name1", Age = 31}, new MyNode()

        {Id = 2, Name = "name2", Age = 2}, new MyNode()

        {Id = 3, Name = "name3", Age = 23}, new MyNode()

        {Id = 4, Name = "name4", Age = 34}, new MyNode()

        {Id = 5, Name = "name5", Age = 5}, new MyNode()

        {Id = 6, Name = "name6", Age = 6}, new MyNode()

        {Id = 7, Name = "name7", Age = 7}, new MyNode()

        {Id = 8, Name = "name8", Age = 8}, };

        // ...Stuff to get nodes

        // If I have this kind of linq, it's ok, but current sort is Fixed (Func<MyNode, int> in this example)

        var result = LstNodes.Where(isAgeOk).Distinct().OrderBy(currentSort).ToList();

        foreach (var entry in result) {

            Console.WriteLine(entry.ToString());

        }

​

    }

}