C#通用验证码

yanzhengma.aspx

<img src="aa/CheckCode.aspx" />
          <asp:TextBox ID="txtCode" runat="server"    ></asp:TextBox>
          <asp:Button ID="Button1" runat="server" OnClick="Button1_Click" Text="Button" />

 

yanzhengma.aspx.cs

string code = txtCode.Text;
          if (String.Compare(code, Request.Cookies["CheckCode"].Value, false) == 0) //String.Compare方法 true:不区分大小,false 区分大小西。前面大值大于零，后面大值小于零。相等则等于零
          {
              Response.Write("<script>alert('验证码正确')</script>");
          }
          else
          {
                         Response.Write("<script>alert('验证码错误')</script>");
          }

CheckCode.aspx.cs

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.Drawing;

public partial class UserPrivileges_CheckCode : System.Web.UI.Page
{
       protected void Page_Load(object sender, EventArgs e)
       {
           this.CreateCheckCodeImage(GenerateCheckCode());
       }
       private string GenerateCheckCode()
       {
           int number;
           char code;
           string checkCode = String.Empty;

           System.Random random = new Random();

           for (int i = 0; i < 5; i++)
           {
               number = random.Next();

               if (number % 2 == 0)
                   code = (char)('0' + (char)(number % 10));
               else
                   code = (char)('A' + (char)(number % 26));

               checkCode += code.ToString();
           }

           Response.Cookies.Add(new HttpCookie("CheckCode", checkCode));

           return checkCode;
       }
       private void CreateCheckCodeImage(string checkCode)
       {
           if (checkCode == null || checkCode.Trim() == String.Empty)
               return;

           System.Drawing.Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling(checkCode.Length * 12.5), 22);
           Graphics g = Graphics.FromImage(image);
           try
           {
               //生成随机生成器

               Random random = new Random();

               //清空图片背景色

               g.Clear(Color.White);

               //画图片的背景噪音线

               for (int i = 0; i < 25; i++)
               {
                   int x1 = random.Next(image.Width);
                   int x2 = random.Next(image.Width);
                   int y1 = random.Next(image.Height);
                   int y2 = random.Next(image.Height);

                   g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);
               }

               Font font = new System.Drawing.Font("Arial", 12, (System.Drawing.FontStyle.Bold | System.Drawing.FontStyle.Italic));
               System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2f, true);
               g.DrawString(checkCode, font, brush, 2, 2);

               //画图片的前景噪音点

               for (int i = 0; i < 100; i++)
               {
                   int x = random.Next(image.Width);
                   int y = random.Next(image.Height);

                   image.SetPixel(x, y, Color.FromArgb(random.Next()));
               }

               //画图片的边框线

               g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);

               System.IO.MemoryStream ms = new System.IO.MemoryStream();
               image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
               Response.ClearContent();
               Response.ContentType = "image/Gif";
               Response.BinaryWrite(ms.ToArray());

           }
           finally
           {
               g.Dispose();
               image.Dispose();
           }
       }
}