Update Database - Deleting existing data and adding new data with entityframework

Question

I have StudentRegistration Model Class as follows

public partial class StudentRegistration
{
    public StudentRegistration()
    {            
        this.StudentReceipts = new HashSet<StudentReceipt>();            
    }

    public int Id { get; set; }
    public Nullable<int> StudentWalkInnID { get; set; } 
    ...
    ...  

    public virtual ICollection<StudentReceipt> StudentReceipts { get; set; }

}
public partial class StudentReceipt
{
    public int Id { get; set; }
    public Nullable<int> StudentRegistrationID { get; set; }
    ...
    ...    

    public virtual StudentRegistration StudentRegistration { get; set; }
}

I was trying to delete existing studentreceipt list and add new list.The new studentreceipt list is adding properly in the database but the existing studentreceipt list is not getting deleted from the database and the StudentRegistrationId of existing studentreceipt list is set to null.

I want to delete the existing studentreceipt list from the database and add new list.How can I do it ?

This is what I have tried

using (TransactionScope _ts = new TransactionScope())
{
  _dbRegn = _db.StudentRegistrations
    .Where(r => r.Id == Id).FirstOrDefault();
  if (_dbRegn != null)
  {                      
    //Remove existing receipts
    foreach (var _existingReceipt in _dbRegn.StudentReceipts.ToList())
    {
      _dbRegn.StudentReceipts.Remove(_existingReceipt);
    }                           

    //adding new receipt
    foreach (var _receipt in mdlCourseInterchange.StudentReceiptList)
    {
      StudentReceipt _studReceipt = new StudentReceipt();
      //...
      //...
      _dbRegn.StudentReceipts.Add(_studReceipt);
    }
    //...
    //..

    db.Entry(_dbRegn).State = EntityState.Modified;
    int j = _db.SaveChanges();
    if (j > 0)
    {
      _ts.Complete();
      return Json(new { message = "success" }, JsonRequestBehavior.AllowGet);
    }
  }
}

As I have mentioned above the new studentreceipt list is adding properly in the database but the existing studentreceipt list is not getting deleted from the database .Infact the StudentRegistrationId of existing studentreceipt list is set to null. — ksg
– ksg, Commented Oct 19, 2016 at 14:08
So are there any StudentReceipts in _dbRegn.StudentReceipts.ToList()? — Mark C.
– Mark C., Commented Oct 19, 2016 at 14:13
Yes there will be StudentReceipts in _dbRegn.StudentReceipts.ToList().And I want to delete the existing list and add the new list — ksg
– ksg, Commented Oct 19, 2016 at 14:16
As @MarkC. suggest, if lazy loading is disabled (I suppose that), when you execute this _dbRegn = _db.StudentRegistrations.Where(r => r.Id == Id).FirstOrDefault(); you are not including the StudentReceipts list property. So you are removing nothing. — Jose Alonso Monge
– Jose Alonso Monge, Commented Oct 19, 2016 at 14:16
@JoseAlonsoMonge As you can see I am using virtual keyword for Student Receipt Collection.So I think include is not required here — ksg
– ksg, Commented Oct 19, 2016 at 14:20

Sampath · Accepted Answer · 2016-10-19 14:35:21Z

1

You can try as shown below.

using (TransactionScope _ts = new TransactionScope())
{
  _dbRegn = _db.StudentRegistrations.Where(r => r.Id == Id).FirstOrDefault();

  if (_dbRegn != null)
  {                      
    //Remove existing receipts
    foreach (var _existingReceipt in _dbRegn.StudentReceipts.ToList())
    {
      __db.StudentReceipts.Remove(_existingReceipt);
    }                           

    //adding new receipt
    foreach (var _receipt in mdlCourseInterchange.StudentReceiptList)
    {
      StudentReceipt _studReceipt = new StudentReceipt();
      //...
      //...
      _db.StudentReceipts.Add(_studReceipt);
    }
    //...
    //..

    int j = _db.SaveChanges();
    if (j > 0)
    {
      _ts.Complete();
      return Json(new { message = "success" }, JsonRequestBehavior.AllowGet);
    }
  }
}

answered Oct 19, 2016 at 14:35

Sampath

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2 Comments

ksg Over a year ago

Thanks for your response mate.I have a small doubt , if accidentally something went wrong after removal of studentreceipt and before addinng new receipt,will the existing receipt will get deleted or it will get deleted only after _ts.Complete()

Sampath Over a year ago

It will happen after _ts.Complete().If any one of the operation fails then all operations will be rolled back.that is the key advantage of using transactions.

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