Hi malar,
Check this example. Now please take its reference and correct your code.
Database
For this example I have used of Northwind database that you can download using the link given below.
Download Northwind Database
Model
public class CustomerModel
{
    public string CustomerID { get; set; }
    public string ContactName { get; set; }
    public string City { get; set; }
    public List<Order> Orders { get; set; }
}
Controller
public class HomeController : Controller
{
    // GET: Home
    public ActionResult Index()
    {
        using (NorthwindEntities entites = new NorthwindEntities())
        {
            List<CustomerModel> model = new List<CustomerModel>();
            foreach (Customer customer in entites.Customers.Take(5))
            {
                model.Add(new CustomerModel
                {
                    CustomerID = customer.CustomerID,
                    ContactName = customer.ContactName,
                    City = customer.City,
                    Orders = entites.Orders.Where(o => o.CustomerID == customer.CustomerID).Take(5).ToList()
                });
            }
            ViewBag.ProjectList = model;
            return View();
        }
    }
}
View
@using Nested_Data_ModalPopup_MVC.Models
@{
    Layout = null;
}
<!DOCTYPE html>
<html>
<head>
    <meta name="viewport" content="width=device-width" />
    <title>Index</title>
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.2/css/bootstrap.min.css" />
    <script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
    <script type="text/javascript" src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.2/js/bootstrap.min.js"></script>
</head>
<body>
    <table class="table">
        <tr>
            <th>Customer Id</th>
            <th>Name</th>
            <th>City</th>
            <th>Orders</th>
        </tr>
        <tbody>
            @foreach (CustomerModel customer in ViewBag.ProjectList)
            {
                <tr>
                    <td>@customer.CustomerID</td>
                    <td>@customer.ContactName</td>
                    <td>@customer.City</td>
                    <td>
                        <button type="button" class="btn btn-primary" data-toggle="modal"
                                data-target="#@customer.CustomerID">
                            View
                        </button>
                        <div class="modal fade" id="@customer.CustomerID">
                            <div class="modal-dialog modal-dialog-centered">
                                <div class="modal-content">
                                    <div class="modal-header">
                                        <h4 class="modal-title">Order Details</h4>
                                        <button type="button" class="close" data-dismiss="modal">×</button>
                                    </div>
                                    <div class="modal-body">
                                        <table class="table">
                                            <tr>
                                                <th>Order Id</th>
                                                <th>Freight</th>
                                            </tr>
                                            <tbody>
                                                @foreach (Order order in customer.Orders)
                                                {
                                                    <tr>
                                                        <td>@order.OrderID</td>
                                                        <td>@order.Freight</td>
                                                    </tr>
                                                }
                                            </tbody>
                                        </table>
                                    </div>
                                    <div class="modal-footer">
                                        <button type="button" class="btn btn-secondary" data-dismiss="modal">Close</button>
                                    </div>
                                </div>
                            </div>
                        </div>
                    </td>
                </tr>
            }
        </tbody>
    </table>
</body>
</html>
Screenshot
