1、写一个验证码，前台什么都不用写，这是CreateVerificationCode_Page.aspx.cs后台代码
using System;
using System.Collections;
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;
namespace 验证码
{
public partial class CreateVerificationCode_Page : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
// 在此处放置用户代码以初始化页面
CreateCheckCodeImage(GenerateCheckCode(5));//charNum=5,
Session["CheckCode"] = GenerateCheckCode(5);
}
#region Web 窗体设计器生成的代码
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 EventHandler(Page_Load);
}
#endregion
private string GenerateCheckCode( int charNum)//charNum是验证码要显示的多少个字母或数字
{
int number;
char code;
string checkCode = String.Empty;
Random random = new Random();
for (int i = 0; i < charNum; i++)
{
number = random.Next();
if (number % 2 == 0)//转换成ASCII码得到相加后的数 再转换成字符char
{
int x = number % 10;
if (x == 0 || x == 1)
{
code = (char)(‘0‘ + (char)(3));
}
else
{
code = (char)(‘0‘ + (char)(number % 10));
}
}
else
{
int y = number % 26;
if (y == 8 || y == 14)
{
code = (char)(‘A‘ + (char)(0));
}
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)), 20); Graphics g = Graphics.FromImage(image);
try
{
Random random = new Random();//生成随机生成器
g.Clear(Color.White);//清空图片背景色
for (int i = 0; i < 2; i++)//画图片的背景噪音线
{
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.Black), x1, y1, x2, y2);
}
Font font = new System.Drawing.Font("Arial", 12, (System.Drawing.FontStyle.Bold));
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);
for (int i = 0; i < 100; i++)//画图片的前景噪音点
{
int x = random.Next(image.Width);
int y = random.Next(image.Height);
image.SetPixel(x, y, Color.FromArgb(random.Next()));
}
g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);//画图片的边框线
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();
}
}
}
}
2、用到验证码的页面
（1）Login_Page.aspx前台
<script language="javascript">//看不清换一个实现
function change()
{
var img = document.getElementById("imgCode");
img.src=img.src+‘?‘;
}
</script>
<tr>
<td align="right">VerificationCode:</td>
<td><input type="text" runat="server" id="txtCode" style="width:128px" maxlength="4" /></td>
<td>
<table>
<tr>
<td>
<img alt=‘‘ src="CreateVerificationCode_Page.aspx" id="imgCode"/>
</td>
<td>
<a href="javascript:change();" style="font-size:12px">NotClear?</a>//看不清换一个实现
</td>
</tr>
（2）Login_Page.aspx.cs后台
protected void btnLogin_Click(object sender, EventArgs e)//点击登录验证输入的验证码是否有误
{
string checkcode = Session["CheckCode"].ToString();
if (txtCode.Value.Equals(checkcode, StringComparison.OrdinalIgnoreCase))//判断输入的与验证码是否相等
{
Response.Write("<script>alert(‘Verification code input correct!‘)</script>");
}
else
{
Page.ClientScript.RegisterClientScriptBlock(ClientScript.GetType(), "myscript", "<script>alert(‘Verification code input incorrect!‘)</script>");
}
}
字母汉子组合的验证码，包括实现看不清换一个的功能