Untitled

using System;
using System.Collections.Generic;
using System.Data;

public class Parent
{
    public int ParentId { get; set; }
    public string ParentName { get; set; }
    public List<Child> Children { get; set; } = new List<Child>();
}

public class Child
{
    public int ChildId { get; set; }
    public string ChildName { get; set; }
}

public class Example
{
    public static List<Parent> MapToParentChild(DataTable dataTable)
    {
        var parents = new Dictionary<int, Parent>();

        foreach (DataRow row in dataTable.Rows)
        {
            int parentId = Convert.ToInt32(row["ParentId"]);
            string parentName = row["ParentName"].ToString();
            int childId = Convert.ToInt32(row["ChildId"]);
            string childName = row["ChildName"].ToString();

            // Check if the parent already exists
            if (!parents.ContainsKey(parentId))
            {
                parents[parentId] = new Parent
                {
                    ParentId = parentId,
                    ParentName = parentName
                };
            }

            // Add the child to the parent's list
            parents[parentId].Children.Add(new Child
            {
                ChildId = childId,
                ChildName = childName
            });
        }

        return new List<Parent>(parents.Values);
    }
}