可以登录就是不能显示登录名！
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; 
using System.Web.Caching; 


public partial class top : System.Web.UI.Page 
{ 
  DBClass obj = new DBClass(); 
  protected void Page_Load(object sender, EventArgs e) 
  {  
  SqlConnection Conn = obj.GetConnection(); 

  if (!IsPostBack) 
  { 
  if (Session["username"] != null) 
  // first.Attributes.Add("onclick", "openwin1()"); 
  { 
  logintag.Text = "欢迎" + Session["username"].ToString() + "登录！"; 
  Conn.Open(); 
  SqlDataAdapter loginAdp = new SqlDataAdapter("select * from UTable", Conn); 
  DataSet loginDS = new DataSet(); 
  loginAdp.Fill(loginDS, "UTable"); 
  Conn.Close(); 
   
  } 
  else 
  { 
  logintag.Text = "你还没有登录！"; 
  } 
  } 
  } 
} 


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;
using System.Drawing;
using System.Web.Caching;

public partial class left : System.Web.UI.Page
{
  DBClass obj = new DBClass();
  protected void Page_Load(object sender, EventArgs e)
  {
  if (!IsPostBack)
  {
  TBXlogin.Text = "";
  TBXpassword.Text = "";
  TBXyan.Text = "";

  }
  }
  protected void BTNlogin_Click(object sender, EventArgs e)
  {
  //HttpCookieCollection cookies = Request.Cookies;
  // string tmp = cookies["ImageV"].Value;
  //if (Seesion["CheckCode"].ToString() == TBXyan.Text)
  if (String.Compare(Session["CheckCode"].ToString(), TBXyan.Text.Trim(), true) != 0)
  {
  Response.Write("<script>alert('验证码错误!')</script>");


  }
  else
  {
  int i = this.CheckLogin(TBXlogin.Text, TBXpassword.Text);
  if (i > 0)
  {
  Session["username"] = TBXlogin.Text.Trim();
  // Response.Write("<script>alert('DNEG!')</script>");
   
  }
  else
  {
  Response.Write("<script>alert('用户名称或密码错误！！！')</script>");
  }
  }
  }
  public int CheckLogin(string login