Disable linkbutton if perticular value exists in database table and enable if not

 public void deselect()
    {
        dl.stu_id = Convert.ToInt16(Session["Stu_id"]);
        DataTable dt = new DataTable();
        dt = bl.exam_disable(dl);
        foreach (System.Data.DataRow row in dt.Rows)
        {
            foreach (GridViewRow gr in GridView1.Rows)
            {
                string s1 = row["Exam_id"].ToString();
                Label l2 = (Label)GridView1.Rows[gr.RowIndex].FindControl("Label3");
                LinkButton l1 = (LinkButton)GridView1.Rows[gr.RowIndex].FindControl("linkselect");
                if (s1 == l2.Text)
                {
                    l1.Enabled = false;
                }              
            }
        }
    }

public void retake()
    {
        foreach (GridViewRow gr in GridView1.Rows)
        {
            LinkButton l3 = (LinkButton)GridView1.Rows[gr.RowIndex].FindControl("lnkretake");
            LinkButton l1 = (LinkButton)GridView1.Rows[gr.RowIndex].FindControl("linkselect");
            if (l1.Enabled == true)
            {              
                l3.Enabled = false;
            }
            else
            {
                l3.Enabled = true;
            }
        }
    }