static void Main()
{
// 7.Try to open two different data contexts and perform concurrent changes on the same records.
// What will happen at SaveChanges() ?
// How to deal with it ?
using (var northwind1 = new NorthwindEntities())
{
using (var northwind2 = new NorthwindEntities())
{
Console.WriteLine(new string('-', 35));
Console.WriteLine("First context");
Console.WriteLine(new string('-', 35));
var person1 = northwind1.Employees.FirstOrDefault();
Console.WriteLine("Initial:{0}", person1.FirstName);
person1.FirstName = "XAXAXA";
Console.WriteLine("Changed:{0}", person1.FirstName);
// Change by Entity state Unchanged Modified Detached
var dbEntry = northwind1.Entry(person1);
dbEntry.State = EntityState.Unchanged;
northwind1.SaveChanges();
Console.WriteLine(new string('-', 35));
Console.WriteLine("Second context");
Console.WriteLine(new string('-', 35));
var person2 = northwind2.Employees.FirstOrDefault();
Console.WriteLine("Initial:{0}", person2.FirstName);
person2.FirstName = "UHAHAH";
Console.WriteLine("Changed:{0}", person2.FirstName);
northwind2.SaveChanges();
}
}
}
private static void DeleteCustomer(string customerId)
{
using (var northwindEntities = new NorthwindEntities())
{
Customer customer = GetCustomerById(northwindEntities, customerId);
northwindEntities.Customers.Remove(customer);
northwindEntities.SaveChanges();
}
}
private static string CreateNewCustomer(string customerId, string companyName, string contactName)
{
using (var northwindEntities = new NorthwindEntities())
{
Customer newCustomer = new Customer
{
CustomerID = customerId,
CompanyName = companyName,
ContactName = contactName
};
northwindEntities.Customers.Add(newCustomer);
northwindEntities.SaveChanges();
return newCustomer.CustomerID;
}
}
private static void ModifyCustomerName(string customerId, string companyName, string contactName)
{
using (var northwindEntities = new NorthwindEntities())
{
Customer customer = GetCustomerById(northwindEntities, customerId);
customer.CompanyName = companyName;
customer.ContactName = contactName;
northwindEntities.SaveChanges();
}
}