Background colors in devexpress grid - winforms grid

Question

ID      Subject     Marks
1000    English       65
1000    Physics       70
1000    Chemistry     75
1001    English       78
1001    Physics       71
1001    Chemistry     60
1002    English       85
1002    Physics       80
1002    Chemistry     79

I want to give background colors (in an alternative manner) based on the value of the ID. If the entries are for 1000, then i would like to give 1000 entries a background color, say for example cyan, then for ID 1001 entries, a different color, then again for 1002, give the same background color(or may be a different one).

I use this below code, however, i don't get the background colors correctly. I get all the rows in the grid with background color as cyan.

Any thoughts?

private void gridView1_RowStyle(object sender, DevExpress.XtraGrid.Views.Grid.RowStyleEventArgs e)
        {
                    ColumnView View = dataGrid.MainView as ColumnView;
                        DevExpress.XtraGrid.Columns.GridColumn col = View.Columns["ID"];
                        for (int i = 0; i <= gridView1.DataRowCount - 1; i++)
                        {
                            if (gridView1.GetRowCellValue(i, col) != gridView1.GetRowCellValue((i + 1), col))
                            {
                                e.Appearance.BackColor = Color.LightCyan;
                            }
                        if (i == gridView1.DataRowCount) break;
                        }

        }

Answer 1

The RowStyle event is already raised for each row - http://documentation.devexpress.com/#WindowsForms/DevExpressXtraGridViewsGridGridView_RowStyletopic

RowStyleEventArgs e (e.RowHandle) can also be negative when dealing with RowGroups http://documentation.devexpress.com/#WindowsForms/CustomDocument695

Each iteration of your loop was using e.RowHandle without checking for negative values - which was changing the back color of the entire column.

I modified your code below to a version that produces an alternating row color pattern on even rows based on the ID column.

     private void dataGrid_RowStyle(object sender, DevExpress.XtraGrid.Views.Grid.RowStyleEventArgs e)
    {
        if (e.RowHandle >= 0)
        {
            ColumnView View = dataGrid.MainView as ColumnView;
            DevExpress.XtraGrid.Columns.GridColumn col = View.Columns["ID"];
            if (Convert.ToInt32(gridView1.GetRowCellValue(e.RowHandle, col)) % 2 == 0)
            {
                e.Appearance.BackColor = Color.LightCyan;
            }
            else
            {
                e.Appearance.BackColor = Color.White;
            }
        }
    }

Answer 2

Been a while since I worked with DX stuff, but that event looks like something that's raised per row and so what your code is actually doing is repainting multiple times - I would guess this is possibly part of the problem.

Check this link, it shows how to do it: http://documentation.devexpress.com/#windowsforms/DevExpressXtraGridViewsGridGridView_RowStyletopic

AS you will see in the example they give, you can address the current row in this handler, and you don't need to loop all the rows.