BindingSource CurrentChanging!

BindingSource CurrentChanging!

• andersrosten

  Hi,
  
  I don't know what Control you've got. Maybe you have something like Validating
  

• Joe_Elwell

  This post was made two years ago... Um, is there a work around for this yet I want to do some validation when the user tries to move off the current record and need to cancel the move if the validation isn't met...or have we been working on better things like wpf

  
  
  

• Peter88

  Hi,

  i had the same problem. It would be really great to have an Event like "CurrentChanging" in the BindingSource component. Unfortunately it seems not to be too important for Microsoft, to implement that event.

  Microsoft: Consider this:

  When the user made changes to the current record/object and moves to the next record the current record/object is stored on the database. The record/object is validated on the database side. Only if the validation was sucessful the user is moved to the next record.

  In the meantime i thought about the following solution

  - Override BindingSource

  - Add a new Event CurrentChanging(seender as Object, e as CanceelEventArgs)

  - Override the Procedure OnCurrentChanged (which raises the event CurrentChanged)

  - Move immediatly back to the unvalidated record

  - Call the new event CurrentChanging

  - If e.cancel = false move to the record which was desired before

  And here is the code:

  Imports System.ComponentModel
  Public Class BindingSourceX
  Inherits System.Windows.Forms.BindingSource

  #Region " Constructors "

  'BindingSourceX should have the same constructors as BindingSource
  Public Sub New()
  MyBase.New()
  End Sub

  Public Sub New(ByVal container As System.ComponentModel.IContainer)
  MyBase.New(container)
  End Sub

  Public Sub New(ByVal dataSource As Object, ByVal dataMember As String)
  MyBase.New(dataSource, dataMember)
  End Sub

  #End Region

  #Region " Private Fields "

  Private _Move As Boolean = False
  Private _StoredPosition As Integer = -1
  Private _StoredCurrent As Object = Nothing

  #End Region

  #Region " CurrentChanging Event "

  Public Event CurrentChanging(ByVal Sender As Object, ByVal e As CancelEventArgs)

  Protected Overridable Sub OnCurrentChanging(ByVal e As System.ComponentModel.CancelEventArgs)
  RaiseEvent CurrentChanging(Me, e)
  End Sub

  #End Region

  Protected Overrides Sub OnPositionChanged(ByVal e As System.EventArgs)
  'Overriding OnPositionChanged without calling the underlying base procedure
  'prevents from uncontrolled executions of PositionChanged Event
  'With other words: MyBase.OnPositionChanged is called by OnCurrentCahanged only.
  End Sub

  Protected Overrides Sub OnCurrentChanged(ByVal e As System.EventArgs)
  If _Move _
  OrElse _StoredCurrent Is Nothing _
  OrElse _StoredPosition > (Me.Count - 1) Then
  'Move to the desired record (by calling the base procedure) if one of the following conditions is true:
  '- _Move is set to true
  '- _StoredCurrent is nothing (No current record and user adds a new row)
  '- _StoredPosition > (Count - 1) (User has deleted the last record)
  MyBase.OnCurrentChanged(e)

  'Position has changed, too
  MyBase.OnPositionChanged(e)

  'Store new values
  _StoredCurrent = Me.Current
  _StoredPosition = Me.Position
  ElseIf _StoredPosition = Me.Position AndAlso Not _StoredCurrent.Equals(Me.Current) Then
  'Move to the desired record (by calling the base procedure)
  'if one of the following conditions is true:
  '- _StoredPosition = aspirated position but _StoredCurrent <> aspirated object (user has deleted a record in the middle)
  MyBase.OnCurrentChanged(e)

  'Position has not changed this time

  'Store new values
  _StoredCurrent = Me.Current
  ElseIf _StoredPosition <> Me.Position Then
  'Store the desired position
  Dim p As Integer = Me.Position

  'Move immediately back to previously stored position
  Me.Position = _StoredPosition

  'Raise CurrentChanging Event
  Dim ce As New CancelEventArgs
  OnCurrentChanging(ce)

  'Move to the aspirated position if the move was not canceled
  If Not ce.Cancel Then
  _Move = True
  Me.Position = p
  _Move = False
  End If
  Else
  'Nothing happens when immediatly moving back to the stored position
  Debug.Print("Internal move")
  End If
  End Sub

  End Class
  

  
  

• Poek

  Hi Linda,
  
  I have a DataGridView bind to a BindingSource in the windows form, when the current row of the DataGridView is changed, the CurrentChanged event of BindingSource is fired.
  
  i want to validate current row before it changed to cancel changing current row. the CurrentChanged event is fired after that.
  
  is there a solution to solve the problem

  
  

• Yan SW

  No, you'll need to handle the CellValidating or RowValidating event on the DataGridView.
  
  -mark
  DataGridView Program Manager
  Microsoft
  This post is provided "as-is"

  
  
• BindingSource CurrentChanging!