asp.net: gridView rotate background color. setting a index column in a DataTable?

two questions about grindView and dataTable.

1. how can i set a dataTable index which always counts one up? e.g. i make a column: Columns.Add(new DataColumn("#")); and when i add a row, the # column is automatically increased?
2. how can i rotate the background color in a g开发者_如何学运维ridView?

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    Set Rowstyle for gridview backcolour e.g.

    <asp:GridView id="gd" runat="Server">

          <RowStyle BackColor="Red" />

    </asp:GridView>

If u want it from Code side then 

For particular Column    
    gridview.Columns[0].ItemStyle.BackColor = System.Drawing.Color.Red;
For grid
       gridview.BackColor = System.Drawing.Color.Red;