Have you been to the jqgrid site? They have an asp.net demo page where you can see many different setups. One of which has checkboxes in it. Also, there are tabs below the grids for ASPX and C# that give you the full page markup and code-behind for the grid. Look at the demo
here[
^]. If you can't figure something out, ask on jqgrid's forums. You will get a much better answer there as the creators of the control answer the questions in those forums.