Datagridviewcell Tooltip doesn't display after modifying image of any cell - winforms

Question

In my winforms application, I loop through the cells of a datagridview and add a tooltip for specific cells based on values in other columns. I do this in the cellformatting event handler, and it worked perfectly. Here is the code:
Private Sub dgvResults_CellFormatting(sender As Object, e As DataGridViewCellFormattingEventArgs) Handles dgvResults.CellFormatting
Select Case dgvResults.Columns(e.ColumnIndex).Name
Case "TradeInValue"
DirectCast(dgvResults.Rows(e.RowIndex).Cells("TradeInValue"), DataGridViewTextBoxCell).ToolTipText = "Min = " & CDec(dgvResults.Item("BB_Min", e.RowIndex).FormattedValue).ToString("$#####.##") & ", Max = " & CDec(dgvResults.Item("BB_Max", e.RowIndex).FormattedValue).ToString("$#####.##")
If Not IsNothing(dgvResults.Item("SelectedTrimIndex", e.RowIndex).FormattedValue) AndAlso dgvResults.Item("SelectedTrimIndex", e.RowIndex).FormattedValue.ToString.Trim.Length > 0 AndAlso CInt(dgvResults.Item("SelectedTrimIndex", e.RowIndex).FormattedValue.ToString) <> -1 Then
If dgvResults.Item("ValueList", e.RowIndex).FormattedValue.ToString.Length > 0 Then
Dim ValueParts() As String = dgvResults.Item("ValueList", e.RowIndex).FormattedValue.ToString.Split("|")
'Dim selectedTrim As String = ValueParts(dgvResults.Item("SelectedTrimIndex", e.RowIndex).FormattedValue)
End If
End If
End Select
End Sub
Then, I added code in the cellpainting event handler to hide specific images, again based on values in the datagridview. Here is that code.
Private Sub dgvResults_CellPainting(sender As Object, e As DataGridViewCellPaintingEventArgs) Handles dgvResults.CellPainting
If e.ColumnIndex >= 0 AndAlso e.RowIndex >= 0 Then
Select Case dgvResults.Columns(e.ColumnIndex).Name
Case "VIN_Pic"
If dgvResults.Rows(e.RowIndex).Cells("VIN_Value").FormattedValue = "" Then
DirectCast(dgvResults.Item(e.ColumnIndex, e.RowIndex), DataGridViewImageCell).Value = New Bitmap(1, 1)
End If
Case "EmailDisplayImage"
If dgvResults.Rows(e.RowIndex).Cells("ListingContactEmail").FormattedValue = "" Then
DirectCast(dgvResults.Item(e.ColumnIndex, e.RowIndex), DataGridViewImageCell).Value = New Bitmap(1, 1)
End If
End Select
End If
End Sub
When this code as added, the tooltips no longer display. The CellToolTipTextNeeded event fires, and it shows the correct text in the argument, but it never displays. Comment out the lines that assign a new image to the datagridviewimagecells, and the tooltips start displaying again.
I hope this explanation was sufficient. Any ideas?

Answer 1

With the below code, you will run into memory and GDI object leaks very easily as a new Bitmap instance is created every time the cell is painted. Also this is causing your ToolTip to be not displayed.
DirectCast(dgvResults.Item(e.ColumnIndex, e.RowIndex), DataGridViewImageCell).Value = New Bitmap(1, 1)
Define the empty bitmap in class level or add as embedded resource and use it.
Dim emptyBitmap As New Bitmap(1, 1);
DirectCast(dgvResults.Item(e.ColumnIndex, e.RowIndex), DataGridViewImageCell).Value = emptyBitmap