using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

    }

    private void GetNodeList(List<CL_Question> lstRoot)

        {

            Node node = null;

            var lstNode = new List<Node>();

            var lstAnswerId = new List<int>();

​

            var ids = lstRoot.Select(m => new List<string>

                {

                    //THIS IS A PROBLEM

                //m.CL_Answer.Select(x => new List<string> {

                    //x.ID_Product.HasValue ? x.ID_Product.Value.ToString() : string.Empty

                //})

                    //m.ID_Product.HasValue ? m.ID_Product.Value.ToString() : string.Empty

                });

        }

}

​

 public partial class CL_Question

    {

        //[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "Instructors")]

        //public CL_Question()

        //{

        //    this.CL_Answer = new HashSet<CL_Answer>();

        //}

        public int ID_Question { get; set; }

        public Nullable<int> ID_Answer { get; set; }

        public Nullable<int> ID_CreditInterview { get; set; }

        public string Code { get; set; }

        public string Name { get; set; }

        public string Description { get; set; }

        public string LastChangedAuthor { get; set; }

        public System.DateTime LastChanged { get; set; }

        public bool Active { get; set; }

        public bool Starting { get; set; }

        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "")]

        //public virtual ICollection<CL_Answer> CL_Answer { get; set; }

        //public virtual CL_Answer CL_Answer1 { get; set; }

        //public virtual CL_CreditInterview CL_CreditInterview { get; set; }

    }

 public class TreeViewModel

    {

        public List<Node> Nodes { get; set; }

    }

    public class Node

    {

        [JsonProperty(PropertyName = "key")]

        public int Key { get; set; }

        [JsonProperty(PropertyName = "parentkey")]

        public int? ParentKey { get; set; }

​

        [JsonProperty(PropertyName = "title")]

        public string Title { get; set; }

​

        [JsonProperty(PropertyName = "folder")]

        public bool Folder { get; set; }

​

        [JsonProperty(PropertyName = "starting")]

        public bool Starting { get; set; }

​

        [JsonProperty(PropertyName = "product")]

        public bool Product { get; set; }

​

        [JsonProperty(PropertyName = "children")]

        public List<Node> Children { get; set; }

    }

​

​