如何使用C#删除数据库中的记录

Question

How do I remove a record?
I need to remove a record that I found by using the foreign key. I stored it as a var but now I can't delete it. Any suggestions?

// POST: Account/Delete/5
[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult Delete(int id, Leerling ll)
{
    var login = from l in db.myLogin
                where id == l.leerlingId
                select l;
    db.myLogin.Remove(login???);
    db.Entry(ll).State = System.Data.Entity.EntityState.Deleted;
    db.SaveChanges();

    return RedirectToAction("Index");// het record verwijderen en redirecten als het gelukt is
}

Answer 1

In your query login a collection of object but to remove a record you need to select a single one so use FirstOrDefault() method to select single record then remove using Remove() method and SaveChanges()

[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult Delete(int id, Leerling ll)
{
    var login = (from l in db.myLogin
                  where id == l.leerlingId
                  select l).FirstOrDefault();
    if(login != null)
    {
       db.myLogin.Remove(login);
       db.Entry(ll).State = System.Data.Entity.EntityState.Deleted;
       db.SaveChanges();
    }


    return RedirectToAction("Index");// het record verwijderen en redirecten als het gelukt is
}

Answer 2

Depends on the database structure. You usually don't want to delete rows but instead have some sort of Status column with one value indicating that the row is deleted. That way you make sure you can't mess something else up.

But if you just want to delete a row you should simply be able to do something like this:

var login = db.myLogin.find(id);
db.myLogin.Remove(login);
db.SaveChanges();

If you are getting some errormessage saying something about a foreign key dependancy you have to delete all the objects reffering to this object first.

Hope this helps.