first of all bind gridview on page_load
then
In the click event write the below code
foreach(Gridviewrow gvr in Gridview1.Rows)
{
if(((CheckBox)gvr.findcontrol("CheckBox1")).Checked == true)
{
int uPrimaryid= gvr.cells["uPrimaryID"];
}
}
you will get primaryid
call selectdata(uPrimaryid) it will return data set
session["ds"]=selectdata(uPrimaryid) or
add it in querystring ...aspx?id=uPrimaryid
redirect to another page
get querstring request.querstring("id")
call method selectdata(uPrimaryid)
bind using gridview.databind();