The Best overloaded method has some invalid arguments using Asp.net MVc - asp.net-mvc

Question

i am creating a simple invententy system in Asp.net Mvc i got the Error as
The best overloaded method match for 'System.Data.Entity.Dbset.Add(WebApplication27.Models.sale)' has some invalid arguments
i got the eror on this line of the project db.sales.Add(sale); i am tring to solve this problem since yesterday but couldn't do it.
sales.class file
**
public partial class sale
{
public int id { get; set; }
public Nullable<int> subtotal { get; set; }
public Nullable<int> pay { get; set; }
public Nullable<int> balance { get; set; }
}
}
**
Sales Controller
[HttpPost]
public ActionResult SaveNew(string data)
{
ajaxModel model = JsonConvert.DeserializeObject<ajaxModel>(data);
bool status = false;
try
{
using (aspposEntities1 db = new aspposEntities1())
{
//insert into Sales table
var sale = new sale
{
subtotal = model.total,
pay = model.pay,
balance = model.balance
};
db.sales.Add(sale);
**db.SaveChanges();** // Error this line
model.data.ForEach( m =>
{
//get the product and deduct the subtotal
int db_product = db.products.First(e => e.id== m.barcode_id);
db_product.qty = db_product.qty - m.qty;
db.sales_product.Add(new sales_product
{
// sales_id = sale.id,
barcode_id = m.barcode_id,
price = m.pro_price,
qty = m.qty,
total = m.total_cost
});
});
db.SaveChanges();
// model.orderid = sale.id;
status = true;
}
TempData["Data"] = model;
return new JsonResult { Data = new { status, message = "Entry saved successfully" } };
//return RedirectToAction("Print", model);
}
catch (Exception e)
{
return new JsonResult { Data = new { status, message = "There was an error saving the Entry" } };
}
}
tableView.cs
public class tableView
{
public string barcode_id { get; set; }
public string pname { get; set; }
public int pro_price { get; set; }
public int qty { get; set; }
public int total_cost { get; set; }
}
public class ajaxModel
{
public List<tableView> data { get; set; }
public int total { get; set; }
public int pay { get; set; }
public int balance { get; set; }
public string orderid { get; set; }
}

Answer 1

Can't leave comments so will have to leave this as an answer:
Your ID column doesn't look like it's being auto incremented, and you've not passed in an ID for it to use. You will either need to use:
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
On the ID column to have it auto generate, or get the current highest id in the table and set it to that +1:
id = db.sales.Max(x=>x.id)+1