private static void Method08()
{
Member member = new Member { Id = 1, Password = "******" + DateTime.Now.Second };
using (var db = new DataContext())
{
//先查询一次，让上下文中存在相同主键的对象
Member oldMember = db.Members.Single(m => m.Id == 1);
Console.WriteLine("更新前：{0}。", oldMember.AddDate);
try
{
DbEntityEntry<Member> entry = db.Entry(member);
entry.State = EntityState.Unchanged;
entry.Property("Password").IsModified = true;
}
catch (InvalidOperationException)
{
ObjectContext objectContext = ((IObjectContextAdapter)db).ObjectContext;
ObjectStateEntry objectEntry = objectContext.ObjectStateManager.GetObjectStateEntry(oldMember);
objectEntry.ApplyCurrentValues(member);
objectEntry.ChangeState(EntityState.Unchanged);
objectEntry.SetModifiedProperty("Password");
}
db.Configuration.ValidateOnSaveEnabled = false;
int count = db.SaveChanges();
db.Configuration.ValidateOnSaveEnabled = true;
Console.WriteLine("操作结果：{0}", count > 0 ? "更新成功。" : "未更新。");
Member newMember = db.Members.Single(m => m.Id == 1);
Console.WriteLine("更新后：{0}。", newMember.Password);
}
}
//针对Method03的InvalidOperationException异常的处理方案
private static void Method04()
{
const string userName = "******";
Member updateMember;
using (var db1 = new DataContext())
{
updateMember = db1.Members.Single(m => m.UserName == userName);
}
updateMember.AddDate = DateTime.Now;
using (var db2 = new DataContext())
{
//先查询一次，让上下文中存在相同主键的对象
Member oldMember = db2.Members.Single(m => m.UserName == userName);
Console.WriteLine("更新前：{0}。", oldMember.AddDate);
DbEntityEntry<Member> entry = db2.Entry(oldMember);
entry.CurrentValues.SetValues(updateMember);
int count = db2.SaveChanges();
Console.WriteLine("操作结果：{0}", count > 0 ? "更新成功。" : "未更新。");
Member newMember = db2.Members.Single(m => m.UserName == userName);
Console.WriteLine("更新后：{0}。", newMember.AddDate);
}
}
private static void Method06()
{
Member member = new Member { Id = 1, Password = "******" + DateTime.Now.Second };
using (var db = new DataContext())
{
DbEntityEntry<Member> entry = db.Entry(member);
entry.State = EntityState.Unchanged;
entry.Property("Password").IsModified = true;
db.Configuration.ValidateOnSaveEnabled = false;
int count = db.SaveChanges();
db.Configuration.ValidateOnSaveEnabled = true;
Console.WriteLine("操作结果：{0}", count > 0 ? "更新成功。" : "未更新。");
Member newMember = db.Members.Single(m => m.Id == 1);
Console.WriteLine("更新后：{0}。", newMember.Password);
}
}
//情景三：在情景二的基础上，上下文2中已存在与外来实体主键相同的数据了，引发InvalidOperationException异常
private static void Method03()
{
const string userName = "******";
Member updateMember;
using (var db1 = new DataContext())
{
updateMember = db1.Members.Single(m => m.UserName == userName);
}
updateMember.AddDate = DateTime.Now;
using (var db2 = new DataContext())
{
//先查询一次，让上下文中存在相同主键的对象
Member oldMember = db2.Members.Single(m => m.UserName == userName);
Console.WriteLine("更新前：{0}。", oldMember.AddDate);
var dbset = db2.Members.Local;
db2.Members.Attach(updateMember);
DbEntityEntry<Member> entry = db2.Entry(updateMember);
Console.WriteLine("Attach成功后的状态：{0}", entry.State); //附加成功之后，状态为EntityState.Unchanged
entry.State = EntityState.Modified;
int count = db2.SaveChanges();
Console.WriteLine("操作结果：{0}", count > 0 ? "更新成功。" : "未更新。");
Member newMember = db2.Members.Single(m => m.UserName == userName);
Console.WriteLine("更新后：{0}。", newMember.AddDate);
}
}