public partial class Login_Page : System.Web.UI.Page
{

    protected void Page_Load(object sender, EventArgs e)
    {
        lblErrorMessage.Visible = false;
        SqlConnection con = new SqlConnection("Data Source=JACKS-PC\SQLEXPRESS;Initial Catalog=CBR;Integrated Security=True");
        con.Open();
    }

    protected void btnLogin_Click(object sender, EventArgs e)
    {
            SqlConnection con = new SqlConnection();
            con.ConnectionString = "Data Source=JACKS-PC\SQLEXPRESS;Initial Catalog=CBR;Integrated Security=True";
            con.Open();
            string userid = txtUsername.Text.Trim();
            string password = txtPassword.Text.Trim();
            SqlCommand cmd = new SqlCommand("select `user id`,`password` from user where `user id`='" + txtUsername.Text + "'and `password`='" + txtPassword.Text + "'", con);
            SqlDataAdapter da = new SqlDataAdapter(cmd);
            DataTable dt = new DataTable();
            da.Fill(dt);
            if (dt.Rows.Count > 0)
            {
                Session["username"] = txtUsername.Text.Trim();
                Response.Redirect("Homepage.aspx");
            }
            else
            {
                lblErrorMessage.Visible = true;
            }
            con.Close();

        }
    }