Datagridview not changing image in cell

Question

I am working with DataGridViewObject in my Windows form, using VB.NET. I have three columns that need to display icons. But, based on some info from row, that icons will be shown or not. My problem is that image won't change when I change its value. Basically, I define my columns like this:

Dim column1 As DataGridViewImageColumn = New DataGridViewImageColumn()
column1.Image = My.Resources.image1
column1.Width = 30
dw.Columns.Add(column1)

Dim column2 As DataGridViewImageColumn = New DataGridViewImageColumn()
column2.Image = My.Resources.image2
column2.Width = 30
dw.Columns.Add(column2)

Dim column3 As DataGridViewImageColumn = New DataGridViewImageColumn()
column3.Image = My.Resources.image3
column3.Width = 30
dw.Columns.Add(column3)

After the data is filled, I am looping through rows, and if I do not want to show the images in that row, I do:

Dim cell1 As DataGridViewImageCell = row.Cells(9)
Dim cell2 As DataGridViewImageCell = row.Cells(10)
Dim cell3 As DataGridViewImageCell = row.Cells(11)

cell1.Value = Nothing
cell2.Value = Nothing
cell3.Value = Nothing

But, my images stay. Anyone knows what am I missing?

Is the DGV bound to something? Your *other* problem is that your app is leaking. — Ňɏssa Pøngjǣrdenlarp, Oct 17 '16 at 14:53
Yes, I set its data source to a DataTable, contents are loaded from db. Sorry, but what do you mean by that 'app is leaking'? — Александар Пламенац, Oct 17 '16 at 14:57
Will the images change from edits? For instance if the user changes a row from Active to Inactive, will one change or are they static? (it *may* be leaking, but it is consuming more resources than it needs to). — Ňɏssa Pøngjǣrdenlarp, Oct 17 '16 at 14:59
They are static. When the data is loaded, they are shown or hidden, and it stays that way. — Александар Пламенац, Oct 17 '16 at 15:02

Reza Aghaei · Accepted Answer · 2016-10-17T15:30:27.487

You are using some unbound DataGridViewImageColumn and as mentioned in documents, The Image property specifies an image that is displayed in cells with no values when the column is not data-bound.

So by setting a cell value to null, you are forcing the cell to show the Image property.

To solve the problem:

For your columns set column.DefaultCellStyle.NullValue = Nothing
Don't set the Image property.
Each time you want to show the image, assign the image to Value property of cell.

You can set value of Cell manually in a loop or using CellFormatting event. For example:

Private Sub DataGridView1_CellFormatting(ByVal sender As System.Object, _
ByVal e As System.Windows.Forms.DataGridViewCellFormattingEventArgs) _
Handles DataGridView1.CellFormatting

    If (e.RowIndex >= 0 AndAlso e.ColumnIndex = 2) Then 
        If (e.RowIndex Mod 2 = 0) Then 'Use any criteria which you need, it's a test
            e.Value = My.Resources.Image1
        Else
            e.Value = DBNull.Value
            e.CellStyle.NullValue = Nothing
        End If
    End If

   ' Do the same for other image columns. 

End Sub

Datagridview not changing image in cell

1 Answers1