Set focus to original datagrid cell after handling data validation with column changing event

In that link, there is a lot of content.

Search for: "'This seems to work :-)"

Use that solution by RonaldBiemand for maximum flexibility.

Thanks for the ideas, including those in RonaldBiemans replies.  I had tried these already, but they do not work when triggered from within the ColumnChanging event.  

For example if you are in cell(1,1) and you edit it with a value that will fail your validation, then click next on cell(4,4), despite putting code in the ColumnChanging event like Me.grdMain.CurrentRowIndex = 0, you will be left with focus in cell(4,4).  If you try to select the cell directly you get an error.  I knew all these techniques prior to asking the question, but thanks anyway.

I have developed a reasonably neat workaround if you don't hate using flags (I love flags), which I show below.  I intend to ask to have this question deleted.  I don't know what is is that as soon as I determine I am stuck and ask a question, I end up working out a reasonable solution.

So thanks again.  

Here's my solution which may be of use to you and others.  It is based on the fact that when you move to a new cell after editing the previous cell you will always fire the CurrentCellChanged event after any ColumnChanging code has finished running.

So every time the CurrentCellChanged event is fired I do one of two things.  If the ReEditNeeded flag is False then I just save the new cell position in case I need to return to it.  If the ReEditNeeded is True then clear the flag back to False and I select the old position.

The validation code in the ColumnChanging event is used to set the ReEditNeeded flag to True if there is a validation issue.

This works really well and does not seem to add any discernable load to the application.


    ' Initialise values used for data validation in the declaration area
    Dim ReEditNeeded = False
    Dim ReturnToCell = New DataGridCell(0, 0)


    ' Add event handlers for the grid for changing of current cell and the table for changing of column
    AddHandler grdMain.CurrentCellChanged, AddressOf Me.MyCellChanging
    AddHandler MainDS.Tables("Images").ColumnChanging, AddressOf Me.MyColChanging


    Private Sub MyCellChanging(ByVal sender As System.Object, ByVal e As System.EventArgs)

        ' NOTE make sure you reset the flag first or you go to the cell twice (unnecessarily)
        If ReEditNeeded Then
            ReEditNeeded = False
            Me.grdMain.CurrentCell = ReturnToCell
        Else
            ReturnToCell = Me.grdMain.CurrentCell
        End If

    End Sub


    Private Sub MyColChanging(ByVal sender As System.Object, ByVal e As System.Data.DataColumnChangeEventArgs)

        Dim ErrMsg = ""

        Select Case e.Column.ColumnName

            Case "ImageNum"

                If IsDBNull(e.ProposedValue) Then
                    ErrMsg = "Image # cannot be empty"
                End If


            Case "Title"

                If Not IsDBNull(e.ProposedValue) Then       ' Must allow nulls here.

                    If e.ProposedValue = "aa" Then
                        ErrMsg = "Title should not equal " & e.ProposedValue
                    End If

                End If

        End Select

        ' If there is a message, you must have invalid data therefore set the flag for re editing, put the old value back and show a message
        If ErrMsg <> "" Then
            ReEditNeeded = True
            e.ProposedValue = e.Row(e.Column.ColumnName)
            MsgBox(ErrMsg, MsgBoxStyle.Critical, "Invalid Data")
        End If

    End Sub


Regards,
Neil

>>  I don't know what is is that as soon as I determine I am stuck and ask a question, I end up working out a reasonable solution.

Can you come up with a reasonable solution to the link I posted above, which is still open for one last issue.. seems like RonaldBiemans has not been coming online for some days..

have you tried using EndActiveEdit, followed by BeginEdit for the cell you want to focus in ?

Hi Rajesh,

I cannot find a reference in the MSDN Library to EndActiveEdit.  I have looked at EndCurrentEdit, CancelCurrentEdit, BeginEdit and EndEdit.  As far as I can tell, all of these are related to controlling the ability to edit and the acceptance or rejection of changes.

My issue is all about re-positioning the focus to a cell in which editing was occurring when the data was invalid.  As I said at the start, I have no problem validating data and rejecting invalid changes.  I am very happy with my solution now.  I allow the user, after giving a warning, to edit the whole datagrid directly rather than record at a time on a separate form.  Sort of super user stuff.  So I will only add the handler when they are in this mode, the overhead then is not detectable among the normal keystrokes and clicks of editing.

Thanks anyway.

Regarding your problem, I must start by saying that I have only been experimenting with .NET for about two months in my lunch times.  I have had no training and have not read any books.  I have just been trying to apply my knowledge of VBA and using help and the web.

Having got that disclaimer out of the way, if I understand you correctly, you are getting a different result using the hot key to using the button. I often find a cure for such seemingly illogical problems using inelegant but satisfactory solutions.

I wonder if the difference in reactions may be explained by the change in focus that occurs when you click the button, does not occur in the same way with the hot key combination.

In your position I would be trying something like this.

As part of the Save button code, change the focus to something other than the grid, maybe even the Save button itself.  If that is no good, maybe try this.

I assume for now that there is at least one existing record in the table, and hence you must be adding a record other than on row 0.
When you click Save, move back one record, then forward again.

      DataGrid1.CurrentRowIndex = DataGrid1.CurrentRowIndex - 1
      DataGrid1.CurrentRowIndex = DataGrid1.CurrentRowIndex +1

      Now update the table.

I know that this is clunky, but hey if it works …

You may need to actually select the cell, not the row, to guarantee a suitable change of focus.

              DataGrid1.CurrentCell = New DataGridCell(DataGrid1.CurrentRowIndex - 1, 0)
              DataGrid1.CurrentCell = New DataGridCell(DataGrid1.CurrentRowIndex + 1, 0)

             You can capture the column you are in if it is not 0.

If you need to be able to add a record to an empty table, you would need to start to add a second record to let you change focus of the first record, then lose the second record.

Let me know how you go.

Good luck.
Neil

I intend to ask to close this question