How can i convert decimal value to text?

I try to create a table of item
public int Id { get; set; }
public string item_name { get; set; }
public decimal item_price { get; set; }
public decimal item_discount { get; set; }
public decimal quantity { get; set; }
public decimal total_amount { get; set; }

from the entry text how can i get the value of total_amount =(item_price*(item_discount/100 )) *quantity ;