In login page Dropdownlist

using System;

using System.Collections.Generic;

using System.Linq;

using System.Data;

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 billing1 : System.Web.UI.Page

{

protected void Page_Load(object sender, EventArgs e)

{

}

protected void Button3_Click(object sender, EventArgs e)

{

String qry="select * from adminlogin where username=@username and password=@password";

SqlConnection con = new SqlConnection(@"Data Source=.\SQLEXPRESS;AttachDbFilename=|Datadirectory|\billing.mdf;Integrated Security=True;User Instance=True");

SqlCommand cmd = new SqlCommand(qry,con);

SqlDataReader rdr;

cmd.Parameters.AddWithValue("@username", textbox3.Text);

cmd.Parameters.AddWithValue("@password", textbox4.Text);

con.Open();

rdr = cmd.ExecuteReader();

if (!rdr.HasRows)

{

con.Close();

Label2.Visible = true;

return;

}

rdr.Read();

Session["Loginid"] = rdr[0].ToString();

con.Close();

Response.Redirect("~\\billing2.aspx");

}

}

using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;

using System.Web.Security;

using System.Web.UI;

using System.Web.UI.WebControls;

using System.Configuration;

using System.Data;

using System.Data.SqlClient;

public partial class billing2 : System.Web.UI.Page

{

protected void Page_Load(object sender, EventArgs e)

{

}

protected void Button1_Click(object sender, EventArgs e)

{

SqlConnection con = new SqlConnection(@"Data Source=.\SQLEXPRESS;AttachDbFilename=|Datadirectory|\billing.mdf;Integrated Security=True;User Instance=True");

string str = "select count(*) from ssss where uname=@uname";

con.Open();

SqlCommand cmd = new SqlCommand(str, con);

cmd.Parameters.AddWithValue("@username", textusername.Text);

Label1.Visible = true;

if (Convert.ToInt32(cmd.ExecuteScalar()) == 0)

{

string qry = "insert into ssss values(@uname,@pwd,@cnpwd)";

SqlCommand cmd2 = new SqlCommand(qry, con);

cmd2.Parameters.AddWithValue("@uname", textusername.Text);

cmd2.Parameters.AddWithValue("@pwd", textpassword.Text);

cmd2.Parameters.AddWithValue("@cnpwd", TextBox1.Text);

cmd2.ExecuteNonQuery();

Response.Redirect("~\\billing6.aspx");

}

con.Close();

}

}