Need help with passing userid/session("userid") on login page

Question

 I am trying to create a login page in C# and want to pass the userid(if it is even necessary) from SQL database through to the next page(reports.aspx) so it knows what user is logged in. The code I have is not working and I am having trouble doing this and need assistance.  Here is my current code, what do I need?

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;  

namespace HSI  

{  

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

    {  

        protected void Page_Load(object sender, EventArgs e)  

        {  

            Session["UserId"] = userid;  

        }  

    private bool AuthenticateUser(string uname, string password)  

    {  

       bool bflag = false;  

       string connString = "Server=portalsql;Database=portal;Integrated Security=True";  

 string strSQL = "select * from  icc_users where username ='" + uname + "' AND password ='" + password + "' and userid = '" + Session["UserId"] + "'";  

       DataSet userDS = new DataSet();  

       SqlConnection m_conn;  

       SqlDataAdapter m_dataAdapter;  

       SqlCommand m_Command;  

       try  

       {  

           m_conn = new SqlConnection(connString);  

           m_conn.Open();  

           m_dataAdapter = new SqlDataAdapter(strSQL, m_conn);  

           m_dataAdapter.Fill(userDS);  

           m_conn.Close();  

       }  

       catch (Exception ex)  

       {  

           userDS = null;  

       }  

       if (userDS != null)  

       {  

           if(userDS.Tables[0].Rows.Count > 0)  

             bflag = true;  

       }  

       return bflag;  

    }  

        protected void Login1_Authenticate1(object sender, AuthenticateEventArgs e)  

        {  

            try  

            {  

                string uname = Login1.UserName.Trim(); //Get the username from the control  

                string password = Login1.Password.Trim(); //get the Password from the control  

                bool flag = AuthenticateUser(uname, password);  

                if (flag == true)  

                {  

                    e.Authenticated = true;  

                    Login1.DestinationPageUrl = "reports.aspx?page='" + Session["UserId"] + "'";  

                }  

                else  

                    e.Authenticated = false;  

            }  

            catch (Exception)  

            {  

                e.Authenticated = false;  

            }  

        }  

}  

    }