ASP.NET登陆验证例子

default.aspx

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title>Untitled Page</title>
</head>
<body>
    <form id="form1" runat="server">
    <asp:Label ID="Label1" runat="server" Text="UserName"></asp:Label>
    <asp:TextBox ID="tbUserName" runat="server" Height="22px" Width="128px"></asp:TextBox>
    <br />
    <asp:Label ID="Label2" runat="server" Text="PassPort"></asp:Label>
    <asp:TextBox ID="tbPassPort" runat="server" EnableTheming="True"
        TextMode="Password"></asp:TextBox>
    <br />
    ValidateCode<asp:TextBox ID="tbValidateCode" runat="server"
        EnableTheming="True"></asp:TextBox>
        <img width="100px" height="25px" src="ValidateImageHandler.ashx"/>
    <br />
    <asp:Button ID="btLogin" runat="server" onclick="btLogin_Click" Text="Login" />
    <br />
    <asp:Label ID="lblResult" runat="server"></asp:Label>
    </form>
</body>
</html>

default.aspx.cs

using System;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Drawing;
using System.Data.SqlClient;
using System.Data.Common;

public partial class _Default : System.Web.UI.Page
{
SqlConnection m_Sqlconn;

    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            this.tbUserName.Text = "";
            this.tbPassPort.Text = "";
        }
            DBConnect();
    }

    public static bool CheckCode(string text)
    {
        string txt = System.Web.HttpContext.Current.Session["strIdentify"] as string;
        return text == txt;
    }

    protected void btLogin_Click(object sender, EventArgs e)
    {
        string l_strUserName = this.tbUserName.Text.Trim();
        string l_strPassPort = this.tbPassPort.Text.Trim();
        string l_strValidateCode = this.tbValidateCode.Text.Trim();

string l_sqlTemp = "select * from tbl_user where username = '" + l_strUserName + "' and [password] = '" + l_strPassPort + "'";

SqlCommand comm = new SqlCommand(l_sqlTemp, m_Sqlconn);

if (comm.ExecuteScalar() != null && CheckCode(l_strValidateCode))
{

this.lblResult.Text = "登陆成功";

}

        else
        {
            //this.lblResult.Text = System.Web.HttpContext.Current.Session["strIdentify"] as string;

this.lblResult.Text="用户登录信息错误，请重新输入";

        }
        m_Sqlconn.Close();
    }

    public void DBConnect()
    {
        string conn = System.Configuration.ConfigurationSettings.AppSettings["DBConnectString"];// "Server=127.0.0.1;user id=sa;password=sa;DataBase=test";

m_Sqlconn = new SqlConnection(conn);

try

        {
            m_Sqlconn.Open();
        }

catch(Exception e)

        {
            this.lblResult.Text = e.ToString();
        }
    }
}

ValidateImageHandler.ashx

<%@ WebHandler Language="C#" Class="ValidateImageHandler" %>

using System;
using System.Web;
using System.Web.SessionState;
using System.Drawing;
using System.Drawing.Imaging;
using System.Text;

/// <summary>
/// ValidateImageHandler 生成网站验证码功能
/// </summary>
public class ValidateImageHandler : IHttpHandler, IRequiresSessionState
{
     int intLength = 4;               //长度
     string strIdentify = "Identify"; //随机字串存储键值，以便存储到Session中
     public ValidateImageHandler()
     {
     }

     /// <summary>
     /// 生成验证图片核心代码
     /// </summary>
     /// <param name="hc"></param>
     public void ProcessRequest(HttpContext hc)
     {
        //设置输出流图片格式
         hc.Response.ContentType = "image/gif";

         Bitmap b = new Bitmap(200, 60);
         Graphics g = Graphics.FromImage(b);
         g.FillRectangle(new SolidBrush(Color.YellowGreen), 0, 0, 200, 60);
         Font font = new Font(FontFamily.GenericSerif, 48, FontStyle.Bold, GraphicsUnit.Pixel);
         Random r = new Random();

         //合法随机显示字符列表
         string strLetters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890";
         StringBuilder s = new StringBuilder();

        //将随机生成的字符串绘制到图片上
         for (int i = 0; i < intLength; i++)
          {
             s.Append(strLetters.Substring(r.Next(0, strLetters.Length - 1), 1));
             g.DrawString(s[s.Length - 1].ToString(), font, new SolidBrush(Color.Blue), i * 38, r.Next(0, 15));
         }

         //生成干扰线条
         Pen pen = new Pen(new SolidBrush(Color.Blue), 2);
         for (int i = 0; i < 1; i++)
         {
             g.DrawLine(pen, new Point(r.Next(0, 199), r.Next(0, 59)), new Point(r.Next(0, 199), r.Next(0, 59)));
        }
         b.Save(hc.Response.OutputStream, ImageFormat.Gif);
         hc.Session["strIdentify"] = s.ToString(); //先保存在Session中，验证与用户输入是否一致
         hc.Response.End();

     }

     /// <summary>
     /// 表示此类实例是否可以被多个请求共用(重用可以提高性能)
     /// </summary>
     public bool IsReusable
     {
         get
         {
             return true;
         }
     }
}

Web.config