Simple Code for Change Password

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Data.SqlClient;
public partial class ChangePassword : System.Web.UI.Page
{
SqlConnection scn = new SqlConnection("Data Source=.;Initial Catalog=Routingmail;Integrated Security=True");
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
scn.Open();
SqlCommand cmd = new SqlCommand("select pwd from Registration where userid='" + Session["userid"].ToString() + "'", scn);
string str = Convert.ToString(cmd.ExecuteScalar());
txtname.Text = str;
scn.Close();
}


}
protected void btnsubmit_Click(object sender, EventArgs e)
{
if (scn.State == ConnectionState.Closed)
{
scn.Open();
}
SqlCommand cmd = new SqlCommand("update Registration set pwd='" + txtpassword.Text + "' where userid='" + Session["userid"].ToString() + "'", scn);
cmd.ExecuteNonQuery();
scn.Close();

}
}