DataGridView only refreshing styles upon cell click

Question

I have a DGV in VB.NET and VS2012. I am attempting to change the cell formatting of various cells dynamically. The following is my code:

Private Sub gridFinancial_CellFormatting(sender As Object, e As DataGridViewCellFormattingEventArgs) Handles gridFinancial.CellFormatting
    Try
        For Each row As chgltrDataSet.gridsourceRow In frmFinBatchChrg.ChgltrDataSet.gridsource.Rows
            If gridFinancial.CurrentRow.Cells("CompBool").Value = True Then
                Me.gridFinancial.CurrentRow.Cells(0).Style.BackColor = Color.Yellow
                Me.gridFinancial.CurrentRow.Cells(1).Style.BackColor = Color.Yellow
                Me.gridFinancial.CurrentRow.Cells(2).Style.BackColor = Color.Yellow
                Me.gridFinancial.CurrentRow.Cells(3).Style.BackColor = Color.Yellow
                Me.gridFinancial.CurrentRow.Cells(4).Style.BackColor = Color.Yellow
                Me.gridFinancial.CurrentRow.Cells(5).Style.BackColor = Color.Yellow
                Me.gridFinancial.CurrentRow.Cells(6).Style.BackColor = Color.Yellow
                Me.gridFinancial.CurrentRow.Cells(7).Style.BackColor = Color.Yellow
                Me.gridFinancial.CurrentRow.Cells(8).Style.BackColor = Color.Yellow

                Me.gridFinancial.CurrentRow.Cells(0).ReadOnly = True
                Me.gridFinancial.CurrentRow.Cells(1).ReadOnly = True
                Me.gridFinancial.CurrentRow.Cells(2).ReadOnly = True
                Me.gridFinancial.CurrentRow.Cells(3).ReadOnly = True
                Me.gridFinancial.CurrentRow.Cells(4).ReadOnly = True
                Me.gridFinancial.CurrentRow.Cells(5).ReadOnly = True
                Me.gridFinancial.CurrentRow.Cells(6).ReadOnly = True
                Me.gridFinancial.Update()
                Me.gridFinancial.Refresh()
    End if

    Catch ex As Exception

    End Try


End Sub

I have read this: http://msdn.microsoft.com/en-us/library/1yef90x0.aspx and maybe I'm missing something, but right now, with that code applied, my DataGridView will only reflect that code if I click one of the affected cells after the DataGridView has been painted. In other words, after the DataGridView has loaded, the cells will only be yellow after I click them (then all of the cells within that row that are supposed to be yellow, appear yellow). Why is this? I'm not sure what I'm doing wrong.

And as a side question, this cell formatting event fires at least 40-50 times before my DGV has even been drawn, and it's only a 6 row DataSource. Isn't there a better event trigger for this? I'm sure my code could be better, but that just seems highly inefficient.

The readonly properties in the above code work fine, so I know the event is triggering correctly.

Answer 1

Instead of setting the cell style like you are you can access the style through the DataGridViewCellFormattingEventArgs.

So something like this:

e.CellStyle.BackColor = Color.Yellow

Another thing to consider is that it is often better to attach your CellFormatting handler from within the DataBindingComplete event.

Private Sub DataGridView1_DataBindingComplete(sender As System.Object, e As System.Windows.Forms.DataGridViewBindingCompleteEventArgs) Handles DataGridView1.DataBindingComplete
    AddHandler DataGridView1.CellFormatting, AddressOf Me.DataGridView1_CellFormatting
End Sub

This addresses some odd behaviour when the visual portion of the DataGridView is rendered by making sure that everything is done before your later events are attached.

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This tip with the DataBindingComplete event should at least reduce the needless calls to CellFormatting - cell formatting fires every time a cell is updated. Once you are all up and running this is only once a user leaves a cell.