public static void DeleteCustomer(Customer input)
 {
     using (var db = new NorthwindEntities())
     {
         db.Customers.Remove(input);
         db.SaveChanges();
     }
 }
 public static Customer GetCustomerById(string id)
 {
     using (var db = new NorthwindEntities())
     {
         var result = db.Customers.FirstOrDefault(x => x.CustomerID == id);
         return result;
     }
 }
 public static void AddCustomer(Customer input)
 {
     using (var db = new NorthwindEntities())
     {
         db.Customers.Add(input);
         db.SaveChanges();
     }
 }
 public static void ModifyCustomer(Customer input)
 {
     using (var db = new NorthwindEntities())
     {
         db.Customers.Attach(input);
         db.Entry(input).State = EntityState.Modified;
         db.SaveChanges();
     }
 }