using System;
using System.Collections.Generic;
using System.Linq;

public class Form1
{
    protected override void OnLoad(EventArgs e)
    {
        base.OnLoad(e);

        var entites = new List<Entite>()
        {
            new Entite() { Nom = "William " },
            new Employe() { Nom = "John doe" }
        };

        DataGridView1.DataSource = entites
            .Select(x => new { nom = x.Nom, x is Employe ? "Employe" : "Entite" })
            .ToList();
    }
}

public class Entite
{
    public string Nom { get; set; }
}

public class Employe : Entite
{

}