/// <summary>
/// 目的: 使用離線模式修改資料
/// </summary>
private static void Practice08()
{
Course course;
using (var db = new ContosoUniversityEntities())
{
course = db.Course.Find(1);
course.Credits = CreditType.Low;
}
//即使attach了, 但沒有修改state, EF還是不會對DB作Update
using (var db = new ContosoUniversityEntities())
{
db.Course.Attach(course);
db.SaveChanges();
Console.WriteLine("Before attached and change state, Credits={0}", db.Course.Find(1).Credits);
}
using (var db = new ContosoUniversityEntities())
{
db.Entry(course).State = System.Data.Entity.EntityState.Modified; //=db.Course.Attach(course);
db.SaveChanges();
Console.WriteLine("After attached, Credits={0}", db.Course.Find(1).Credits);
}
}
/// <summary>
/// 目的: 使用 db.ChangeTracker.Entities() 實作在修改資料後 SaveChanges() 時自動填入 ModifiedOn 欄位的內容
/// </summary>
private static void Practice07()
{
using (var db = new ContosoUniversityEntities())
{
var course = db.Course.Find(1);
course.Credits = CreditType.Low;
var entry = db.Entry(course);
Console.WriteLine("Original Value=" + entry.OriginalValues.GetValue<int>("Credits"));
Console.WriteLine("Current Value=" + entry.CurrentValues.GetValue<int>("Credits"));
Console.WriteLine("State:" + "\t" + entry.State);
db.SaveChanges();
}
}