code for login controls for sql server

protected void Login1_Authenticate(object sender,
AuthenticateEventArgs e)
    {   string u_id=Login1.UserName;
        string pwd=Login1.Password;

        SqlConnection con = new
SqlConnection("uid=sa;pwd=nivt;server=.;database=jobportal");
        try
        {
            con.Open();
            SqlDataAdapter da = new SqlDataAdapter("select *
from rec_registration where rec_username='" + u_id + "'", con);
            DataSet ds = new DataSet();
            da.Fill(ds);
            if (Login1.UserName ==
ds.Tables[0].Rows[0][0].ToString() && Login1.Password ==
ds.Tables[0].Rows[0][1].ToString())
            {
                Session["rec_uid"] = u_id;
                Session["rec_uname"] =
ds.Tables[0].Rows[0][3].ToString();
                Session["rec_type"] =
ds.Tables[0].Rows[0][5].ToString();

               Response.Redirect("rec_home.aspx");
                
            }
            else
            {
                Label2.Text = "Invalid Username/Password:";

            }
        }
        catch(Exception ex)
        {
            Label3.Text = ex.Message.ToString();
            Label2.Text = "Invalid Username";

        }
        finally
        {
            if (con.State == ConnectionState.Open)
            {
                con.Close();
            }
        }

    }