public static string InsertNewCustomer(NorthwindEntities db, Customer customer)
{
if (customer == null)
{
throw new ArgumentNullException("Customer cannot be null.");
}
using (db)
{
db.Customers.Add(customer);
db.Customers.Add(customer);
db.SaveChanges();
return customer.CustomerID;
}
}
public static void UpdateCustomerCompanyName(NorthwindEntities db, string customerID, string newCompanyName)
{
if (string.IsNullOrWhiteSpace(customerID))
{
throw new ArgumentException(string.Format("Invalid ID : {0}.", customerID));
}
using (db)
{
var customer = db.Customers
.FirstOrDefault(c => c.CustomerID == customerID);
if (customer == null)
{
throw new ArgumentException("No such customer with this id.");
}
customer.CompanyName = newCompanyName;
db.SaveChanges();
}
}
public static void Delete(NorthwindEntities db, string customerID)
{
if (string.IsNullOrWhiteSpace(customerID))
{
throw new ArgumentException("Id is null, empty or contains only whitespaces.");
}
using (db)
{
var customer = db.Customers
.FirstOrDefault(c => c.CustomerID == customerID);
if (customer == null)
{
throw new ArgumentException("No such customer with this id.");
}
db.Customers.Remove(customer);
db.SaveChanges();
}
}
//// To deal with this problem next time use Transactions
public static void Main()
{
var db1 = new NorthwindEntities();
var db2 = new NorthwindEntities();
var employeeFromDb1 = db1.Employees.FirstOrDefault();
var employeeFromDb2 = db2.Employees.FirstOrDefault();
Console.WriteLine("Name from db1: {0}", employeeFromDb1.FirstName + " " + employeeFromDb1.LastName);
Console.WriteLine("Name from db2: {0}", employeeFromDb2.FirstName + " " + employeeFromDb2.LastName);
employeeFromDb1.LastName = "context 1";
// Second name will overwrite the first.
employeeFromDb2.LastName = "context 2";
db1.SaveChanges();
db2.SaveChanges();
var dbResult = new NorthwindEntities().Employees.FirstOrDefault();
Console.WriteLine("\nResult: : {0}", dbResult.FirstName + " " + dbResult.LastName);
}
