using System;

using System.Collections.Generic;

using System.Linq;

​

public class MyInfo {

    public MyInfo(string one, string two){

        Prop1 = one;

        Prop2 = two;

    }

    public string Prop1 {get;set;}

    public string Prop2 {get;set;}

    public override string ToString(){

        return $"MyInfo{{Prop1:\"{Prop1}\", Prop2:\"{Prop2}\"}},";

    }

}

​

public class MyTreeNode {

    public MyTreeNode(string text, object tag, bool czeched = false){

        Checked = czeched;

        Text = text;

        Tag = tag;

    }

    public ICollection<MyTreeNode> Nodes {get;set;} = new List<MyTreeNode>();

    public bool Checked {get;set;}

    public string Text {get;set;}

    public object Tag  {get;set;}

}

​

public class Program

{

    public static void Main()

    {

        // Make List

        var list = new List<MyTreeNode>();

        list.Add(new("one", new MyInfo("one", "x:one"), true));

        list.Add(new("two", new MyInfo("two", "x:two"), false));

        var three = new MyTreeNode("three", new MyInfo("three", "x:3"), true);

        three.Nodes = new List<MyTreeNode>{

            new ("3a", new MyInfo("3a", "y:3a"), true),

            new ("3b", new MyInfo("3b", "y:3b"), false),

            new ("3c", new MyInfo("3c", "y:3c"), true),

            new ("3d", new MyInfo("3d", "y:3d"), false)

        };

        var threeE = new MyTreeNode("3e", new MyInfo("3e", "y:3e"), false);

        threeE.Nodes = new List<MyTreeNode>{

            new ("3Ea", new MyInfo("3Ea", "y:3Ea"), true),

            new ("3Eb", new MyInfo("3Eb", "y:3Eb"), false),

            new ("3Ec", new MyInfo("3Ec", "y:3Ec"), true)

        };

        three.Nodes.Add(threeE);

        list.Add(three);

        list.Add(new("four", new MyInfo("four", "x:four"), false));

        list.Add(new("five", new MyInfo("five", "x:five"), true));

        // Select

        foreach(var info in GetSelectedInfo(list).ToList()){

            Console.WriteLine(info);

        }

        Console.WriteLine("Done");

    }

    public static IEnumerable<MyInfo> GetSelectedInfo(ICollection<MyTreeNode> nodes){

        foreach(MyTreeNode node in nodes){

            if(node.Checked && node.Tag is MyInfo info) yield return info;

            if(node.Nodes.Count==0) continue;

            foreach(var subInfo in GetSelectedInfo(node.Nodes)){

                    yield return subInfo;

            }

        }

    }

}