Grid View Check box with link button click

CheckBox chk1;
for (int k = 0; k < gvPackageCourses.Rows.Count; k++)
{
chk1 = ((CheckBox)gvPackageCourses.Rows[k].Cells[2].FindControl("chkBoxCourses"));
chk1.Checked = false;
}
LinkButton sel = ((LinkButton)sender);int rowindex = Int32.Parse(sel.CommandArgument);

Label lblId;
vw_enqueryreg objvw = new vw_enqueryreg();
//objvw.FlushData();
objvw.LoadSql("select courseid from vw_enqueryreg where StudentId='"+rowindex+"'");
////objvw.Where.StudentId.Value = rowindex;
////objvw.Where.StudentId.Operator = VTPLfx.WhereParameter.Operand.Equal;////objvw.Query.Load();int rowno = objvw.DefaultView.ToTable().Rows.Count;
CheckBox chk;
for (int i = 0; i < gvPackageCourses.Rows.Count; i++)
{
chk = ((CheckBox)gvPackageCourses.Rows[i].Cells[2].FindControl("chkBoxCourses"));
//////if(objvw.DefaultView.ToTable().Rows[i][0]==)
for (int j = 0; j < rowno; j++)
{
lblId = ((Label)gvPackageCourses.Rows[i].Cells[0].FindControl("lblprimaryKey"));
long id = long.Parse(lblId.Text);
if (id.ToString() == objvw.DefaultView.ToTable().Rows[j][0].ToString())
{
chk.Checked = true;
}
}
//chk.Checked = true;
}
//int rowIndex = Int32.Parse(link1.CommandArgument);
//for (int i = 0; i < gvEnquiryList.Rows.Count; i++)//{
// int temp = Convert.ToInt32(gvEnquiryList.Rows[i].Cells[2].Text.ToString());
//}