public static void PlayWithDetatch()
{
SoftUniEntities softUniEntities = new SoftUniEntities();
Employee newEmployee = new Employee
{
FirstName = "Vladimir",
LastName = "Georgiev",
JobTitle = "Technical Trainer",
DepartmentID = 1,
HireDate = new DateTime(2013, 12, 16),
Salary = 10000
};
softUniEntities.Employees.Add(newEmployee);
softUniEntities.SaveChanges();
// Now the employee is stored in the database. Let's print its department
Console.WriteLine(newEmployee.Department); // prints "null"
// Find the employee by primary key --> returns the same object (unmodified)
// Still prints "null" (due to caching and identity resolution)
var employeeById = softUniEntities.Employees.Find(newEmployee.EmployeeID);
Console.WriteLine(employeeById.Department); // null (due to caching)
// Find the product by query still uses "identity resolution" (caching)
var employeeFromDb =
(from emp in softUniEntities.Employees
where emp.EmployeeID == newEmployee.EmployeeID
select emp).FirstOrDefault();
Console.WriteLine(employeeFromDb.Department); // null (due to caching)
// Detach the object from the context --> remove it from the cache
((IObjectContextAdapter)softUniEntities).ObjectContext.Detach(newEmployee);
// This change will not be tracked by the context
newEmployee.FirstName = "Vlado";
// This will make no changes in the DB (detatched objects are not tracked)
softUniEntities.SaveChanges();
// Now find the product by primary key (detached entities are not cached)
var detachedEmployee = softUniEntities.Employees.Find(newEmployee.EmployeeID);
Console.WriteLine(detachedEmployee.Department); // works (no caching)
}
public static void Main()
{
var softUniContext = new SoftUniEntities();
var customer = new Town() { TownID = 3 };
softUniContext.Entry(customer).State = EntityState.Deleted;
softUniContext.SaveChanges();
SelectFromSingleTable();
SelectFromMultipleTables();
}
public static void UpdateProject(Project product, string newName)
{
using (SoftUniEntities northwindEntities = new SoftUniEntities())
{
northwindEntities.Projects.Attach(product); // This line is required!
product.Name = newName;
northwindEntities.SaveChanges();
}
}