Winforms Datagridview too slow with ImageColumn

Question

Hi there!

In my winforms app, i have a datagridview that takes about 0.8 seconds to be populated with +/- 5000rows - if all columns are textbox columns.

One of the columns is an integer column, so I decided to change that column to an ImageColumn and in the Cell_formatting event of the grid, I use the following code to determine the appropriate image to display:

private void dgv_CellFormatting(object sender, DataGridViewCellFormattingEventArgs e) {
    if (dgv.Columns[e.ColumnIndex] is DataGridViewImageColumn && e.ColumnIndex == 1) {
        int cellVal = (int)e.Value;
        switch (cellVal) {
            case 1:
                e.Value = Properties.Resources.Pending;
                dgv.Rows[e.RowIndex].Cells[e.ColumnIndex].ToolTipText = "Item pending attention";
                break;
            case 2:
                e.Value = Properties.Resources.Tick
                dgv.Rows[e.RowIndex].Cells[e.ColumnIndex].ToolTipText = "File is available";
                break;
            default:
                break;
        }
    }
}

It works. However, the datagridview now takes almost 5 seconds to populate itself!! and sorting columns just becomes too time consuming. 5 seconds now may not seem like a lot, but the rows will grow to about 30,000 in about 2months time!!

Is there a more efficient way to handle this scenario?

Thank u!

Answer 1

This may not help at all, but you could try doing the e.ColumnIndex == 1 comparison first. Since && is a short-circuiting operator, you won't be evaluating dgv.Columns[e.ColumnIndex] is DataGridViewImageColumn for every column.

Edit: I would really use something like Visual Studio Profiler or some other performance tool to find bottlenecks.

Answer 2

Have you checked that the bottleneck isn't in the reading and (possible) resizing of the images?

If you're displaying the images at 32x32 pixels (say) but they are stored as 128x128 pixels (say) then there will be a resize every time the image is displayed.

Answer 3

If performance is a concern, you may consider using the DataGridView in virtual mode.