How to rollback the deleted record to DataSet in VB.NEt



I have a code to delete a record from DataTable.  First I delete the record using
cmSchool.RemoveAt(cmSchool.Position), and the record is deleted from the DataTable. Then  I delete the record from the underlying database using  m_daSchool.Update(m_dsSchool, "School")
                        m_dsSchool.AcceptChanges()  
Since the record is referenced by children table, so it cannot be deleted.
But the record already disappeared from the DataTable.
Could you please tell me how i can rollback this record to the DataTable?
Thanks

Huer


Imports System
Imports System.IO

Public Class frmUtilities
    Inherits System.Windows.Forms.Form
    Private cmSchool As CurrencyManager
    Private m_dwSchool As DataView
Private Sub frmUtilities_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
           '//-- bound to controls
        m_dwSchool =m_dsSchool.Tables("school").DefaultView
        m_dwSchool.Sort = "SCH_NAME"
        txtSchool.DataBindings.Add("text", m_dwSchool, "sch_name")
        txtSchoolNo.DataBindings.Add("text", m_dwSchool, "sch_id")
        cmSchool = Me.BindingContext(m_dwSchool)
     
    End Sub
 Private Sub btnDelete_Click(ByVal sender As System.Object, ByVal e As System.EventArgs)
        Dim Result As DialogResult
        Result = MessageBox.Show(Me, "Do you want to delete the record", "Delete Record", MessageBoxButtons.YesNo, _
               MessageBoxIcon.Question, MessageBoxDefaultButton.Button1, MessageBoxOptions.RightAlign)
        If Result = DialogResult.No Then Exit Sub
        Try
            If (cmSchool.Count > 0) Then
                cmSchool.RemoveAt(cmSchool.Position)
                 m_daSchool.Update(m_dsSchool, "School")
                m_dsSchool.AcceptChanges()          
        Catch ex As Exception
            MessageBox.Show(ex.Message)
        Finally
            ' mvarConn.Close()
        End Try
    End Sub

     
huerAsked:
Who is Participating?
 
iboutchkineConnect With a Mentor Commented:
I did not try it, but give it a shot

ds.RejectChanges
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EBatistaConnect With a Mentor Commented:
first you dont need to call AcceptChanges() after the Updatemethod from the dataadapter cos it do it for you, so it is extra work.
now to the problem, the dataset provide the method Reject or RejectChange (dont have VS in this PC), you could place it in the catch block:
     
        Catch ex As Exception
            MessageBox.Show(ex.Message)
            m_dsSchool.RejectChanges() ' or m_dsSchool.Reject()
       
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DabasConnect With a Mentor Commented:
Hi huer,
You could save the DataSet to Xml, then if the update fails clear the dataset and reread it from XML

Dabas
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EBatistaCommented:
btw be carefull how you use RejectChanges() cos it will reject all the changes you made to the dataset from the las time was invoked AceptChanges (recall that AcceptChanges is implicitly called from the dataadapter update method), that means that you will lost all the updates and inserts too, you can address that problem doing what dabas says or reflect first all those updated and inserted rows in the database

regards
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huerAuthor Commented:
Could you tell me how to save the DataSet to xml, and then reread it from XML when update fails?
I am new to VB.NET

Please help me.
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iboutchkineCommented:
save
ds.WriteXML("YourXMLfile")

to read back to ds

ds.ReadXML("YourXMLfile")
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