图片验证码

using System;
using System.Collections;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Web;
using System.Web.SessionState;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.HtmlControls;

namespace test
{
    /**//// <summary>
    /// WebForm1 的摘要说明。
    /// </summary>
    public class WebForm1 : System.Web.UI.Page
    {
        private  char[] constant=
        {
                '0','1','2','3','4','5','6','7','8','9','a','b','c','d','e','f','g','h','i','j','k','l','m','n','o',
            'p','q','r','s','t','u','v','w','x','y','z','A','B','C','D','E',
            'F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'
        };
        private void Page_Load(object sender, System.EventArgs e)
        {
            // 在此处放置用户代码以初始化页面
            if(!Page.IsPostBack)
            {
                string VNum=GenerateRandom(5);
                Session["VNum"] = VNum;
                Validate_code(VNum);
            }


            
        }
        private  string GenerateRandom(int length)
        {
            System.Text.StringBuilder sb = new System.Text.StringBuilder(62);
            System.Random r = new Random();
            for(int i=0;i<length;i++)
            {
                sb.Append(constant[r.Next(62)]);
            }
            return sb.ToString();
        }
        private  void Validate_code(string sValue)
        {

            int gHeigth=Int32.Parse((sValue.Length * 13).ToString());
            System.Drawing.Bitmap Img = new System.Drawing.Bitmap(gHeigth,20);
            System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(Img);
            g.DrawString(sValue,new System.Drawing.Font("Arial",12),
                new System.Drawing.SolidBrush(System.Drawing.Color.Blue),3,3);
            System.IO.MemoryStream ms = new System.IO.MemoryStream();
            Img.Save(ms,System.Drawing.Imaging.ImageFormat.Png);
            Response.ClearContent();
            Response.ContentType="image/gif";
            Response.BinaryWrite(ms.ToArray());
            g.Dispose();
            Img.Dispose();
            Response.End();
        }

        Web Form Designer generated code#region Web Form Designer generated code
        override protected void OnInit(EventArgs e)
        {
            //
            // CODEGEN：该调用是 ASP.NET Web 窗体设计器所必需的。
            //
            InitializeComponent();
            base.OnInit(e);
        }
        
        /**//// <summary>
        /// 设计器支持所需的方法 - 不要使用代码编辑器修改
        /// 此方法的内容。
        /// </summary>
        private void InitializeComponent()
        {    
            this.Load += new System.EventHandler(this.Page_Load);
        }
        #endregion
    }
}