BindingSource CurrentChanging!

Question

CurrentChanged event in BindingSource is fired after the position has been changed, while I need something fired before that can cancel the move when the object is not valid

Answer 1

Hi,

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

Answer 2

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?

Answer 3

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"

Answer 4

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

Answer 5

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?

 

Answer 6

After another four and a half years we have yet to see CurrentChanging in BindingSource. Say what if I'm not using DataGridView and working with plain simple control binding; I don't get any ROW-LEVEL Validating event where I could stop the CurrencyManager from moving to the new record.