How can I make datagridview can only select the cells in the same column at a time?

Question

I am using winforms to develop my application. And I set my datagridview control's selectionmode to "CellSelect", and this allow the user to select as many cells as he want which spread over several columns; but I want to constraint my user can only select cells in single column at a time, and there isn't any such kind of selectionmode for me.

So If I want to implement this, how can I extend the datagridview class ? I also think that I can check in eventhandler whenever the selection cells are changed, through which I might make the user can not select cells spread over multiple columns, but this is not that good, I think.

Can any other people help me to find out a better solution ?

Answer 1

Your implementation is okay. This is exactly what I did. Initially I tried to deal with the SetSelected...Core methods, but the details got clumbersome. I settled on the following because 1) it works with little code, 2) doesn't interfere with other code, and 3) simple.

Public Class DataGridView
    Inherits System.Windows.Forms.DataGridView

    Protected Overrides Sub OnSelectionChanged(ByVal e As System.EventArgs)
        Static fIsEventDisabled As Boolean

        If fIsEventDisabled = False Then

            If Me.SelectedCells.Count > 1 Then
                Dim iColumnIndex As Integer = Me.SelectedCells(0).ColumnIndex
                fIsEventDisabled = True
                ClearSelection()
                SelectColumn(iColumnIndex) 'not calling SetSelectedColumnCore on purpose
                fIsEventDisabled = False
            End If

        End If

        MyBase.OnSelectionChanged(e)

    End Sub

    Public Sub SelectColumn(ByVal index As Integer)
        For Each oRow As DataGridViewRow In Me.Rows
            If oRow.IsNewRow = False Then
                oRow.Cells.Item(index).Selected = True
            End If
        Next
    End Sub

End Class