jqGrid uses js with onSelectRow property, please how to select a row and get the asp.net page the id?

jqGrid uses js with onSelectRow property, please how to select a row and
get the asp.net page the id?

I have jqgrid that uses only js script and default.aspx page which display
the grid, IO need badly please as I'm able to view the grid but when I
click on a row on the grid it does identify the id (which I want) but I
cannot retrieve it on the back code of the page (Default.aspx.cs) using:
if (Request.QueryString["cmd"] == "select") it is detected and run the
grid but adding if (Request.QueryString["cmd"] == "delete") it is always
null, there is must be something wrong with the request. Can anybody help
please on this issue? I'll be very appreciated. Tried setting:
jQuery('#htmlTable5').jqGrid('setGridParam', { url:
'Default.aspx?cmd=select&que=1&id=' + id, mytype: 'POST', datatype:
'json'});
But it does not work (I see it inside diagnosing tool like firebug is
exist as que 1 but on page_load it is always null no matter what statement
I use.