i figure it out! ^_^
this is my code!
protected void GridView_milestone_OnSelectedIndexChanged(object sender, EventArgs e)
{
GridViewRow row = GridView_milestone.SelectedRow;
lblmilestone_popup_code.Text = row.Cells[0].Text;
lblmilestone_popup_orderno.Text = row.Cells[1].Text;
lblmilestonename_popup_name.Text = row.Cells[2].Text;
string stat_selected = "";
if (row.Cells[3].Text == "Active")
{
stat_selected = "Active";
}
else if (row.Cells[3].Text == "Inactive")
{
stat_selected = "Inactive";
}
rrd.Items.Clear();
rrd.Items.Add("Active");
rrd.Items.Add("Inactive");
rrd.SelectedValue = stat_selected;
}