asp.net验证码新手教程
1、制作登录页面：
先布局好调用验证码的登录页面（命名：Login.aspx）
注意：验证码位置可以是服务器控件 Image，也可以是html标签写的<img>，但是图片url就是一个页面（命名：ValidateCode.aspx）(将在下面讲述。)
代码如下：
<asp:Image ID=“vcImg” ImageUrl="~/ValidateCode.aspx" runat="server" />
2、编写生成验证码的代码
生成类文件 (命名：validatedCode）
添加以下引用
using System;
using System.Web;
using System.Drawing;
/// <summary>
/// Summary description for validatedCode
/// </summary>
public class validatedCode
{
/// <summary>
/// 验证码长度(默认6个验证码的长度)
/// </summary>
public int Length { get; set; } = 4;
/// <summary>
/// 验证码字体大小(为了显示扭曲效果，默认40像素，可以自行修改)
/// </summary>
public int FontSize { get; set; } = 40;
/// <summary>
/// 边框补(默认1像素)
/// </summary>
public int Padding { get; set; } = 2;
/// <summary>
/// 是否输出燥点(默认不输出)
/// </summary>
public bool Chaos { get; set; } = true;
/// <summary>
/// 输出燥点的颜色(默认灰色)
/// </summary>
public Color ChaosColor { get; set; } = Color.LightGray;
/// <summary>
/// 自定义背景色(默认白色)
/// </summary>
public Color BackgroundColor { get; set; } = Color.White;
/// <summary>
/// 自定义随机颜色数组
/// </summary>
public Color[] Colors { get; set; } = { Color.Black, Color.Red, Color.DarkBlue, Color.Green, Color.Orange, Color.Brown, Color.DarkCyan, Color.Purple };
/// <summary>
/// 自定义字体数组
/// </summary>
public string[] Fonts { get; set; } = { "Arial", "Georgia" };
/// <summary>
/// 自定义随机码字符串序列(使用逗号分隔)
/// </summary>
public string CodeSerial { get; set; } = "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";
#region 产生波形滤镜效果
private const double PI = 3.1415926535897932384626433832795;
private const double PI2 = 6.283185307179586476925286766559;
/// <summary>
/// 正弦曲线Wave扭曲图片（Edit By 51aspx.com）
/// </summary>
/// <param name="srcBmp">图片路径</param>
/// <param name="bXDir">如果扭曲则选择为True</param>
/// <param name="nMultValue">波形的幅度倍数，越大扭曲的程度越高，一般为3</param>
/// <param name="dPhase">波形的起始相位，取值区间[0-2*PI)</param>
/// <returns></returns>
public System.Drawing.Bitmap TwistImage(Bitmap srcBmp, bool bXDir, double dMultValue, double dPhase)
{
System.Drawing.Bitmap destBmp = new Bitmap(srcBmp.Width, srcBmp.Height);
// 将位图背景填充为白色
System.Drawing.Graphics graph = System.Drawing.Graphics.FromImage(destBmp);
graph.FillRectangle(new SolidBrush(System.Drawing.Color.White), 0, 0, destBmp.Width, destBmp.Height);
graph.Dispose();
double dBaseAxisLen = bXDir ? (double)destBmp.Height : (double)destBmp.Width;
for (int i = 0; i < destBmp.Width; i++)
{
for (int j = 0; j < destBmp.Height; j++)
{
double dx = 0;
dx = bXDir ? (PI2 * (double)j) / dBaseAxisLen : (PI2 * (double)i) / dBaseAxisLen;
dx += dPhase;
double dy = Math.Sin(dx);
// 取得当前点的颜色
int nOldX = 0, nOldY = 0;
nOldX = bXDir ? i + (int)(dy * dMultValue) : i;
nOldY = bXDir ? j : j + (int)(dy * dMultValue);
System.Drawing.Color color = srcBmp.GetPixel(i, j);
if (nOldX >= 0 && nOldX < destBmp.Width
&& nOldY >= 0 && nOldY < destBmp.Height)
{
destBmp.SetPixel(nOldX, nOldY, color);
}
}
}
return destBmp;
}
#endregion
#region 生成校验码图片
public Bitmap CreateImageCode(string code)
{
int fSize = FontSize;
int fWidth = fSize + Padding;
int imageWidth = (int)(code.Length * fWidth) + 4 + Padding * 2;
int imageHeight = fSize * 2 + Padding;
System.Drawing.Bitmap image = new System.Drawing.Bitmap(imageWidth, imageHeight);
Graphics g = Graphics.FromImage(image);
g.Clear(BackgroundColor);
Random rand = new Random();
//给背景添加随机生成的燥点
if (this.Chaos)
{
Pen pen = new Pen(ChaosColor, 0);
int c = Length * 10;
for (int i = 0; i < c; i++)
{
int x = rand.Next(image.Width);
int y = rand.Next(image.Height);
g.DrawRectangle(pen, x, y, 1, 1);
}
}
int left = 0, top = 0, top1 = 1, top2 = 1;
int n1 = (imageHeight - FontSize - Padding * 2);
int n2 = n1 / 4;
top1 = n2;
top2 = n2 * 2;
Font f;
Brush b;
int cindex, findex;
//随机字体和颜色的验证码字符
for (int i = 0; i < code.Length; i++)
{
cindex = rand.Next(Colors.Length - 1);
findex = rand.Next(Fonts.Length - 1);
f = new System.Drawing.Font(Fonts[findex], fSize, System.Drawing.FontStyle.Bold);
b = new System.Drawing.SolidBrush(Colors[cindex]);
if (i % 2 == 1)
{
top = top2;
}
else
{
top = top1;
}
left = i * fWidth;
g.DrawString(code.Substring(i, 1), f, b, left, top);
}
//画一个边框 边框颜色为Color.Gainsboro
g.DrawRectangle(new Pen(Color.Gainsboro, 0), 0, 0, image.Width - 1, image.Height - 1);
g.Dispose();
//产生波形（Add By 51aspx.com）
image = TwistImage(image, true, 8, 4);
return image;
}
#endregion
#region 将创建好的图片输出到页面
public void CreateImageOnPage(string code, HttpContext context)
{
System.IO.MemoryStream ms = new System.IO.MemoryStream();
Bitmap image = this.CreateImageCode(code);
image.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
context.Response.ClearContent();
context.Response.ContentType = "image/Jpeg";
context.Response.BinaryWrite(ms.GetBuffer());
ms.Close();
ms = null;
image.Dispose();
image = null;
}
#endregion
#region 生成随机字符码
public string CreateVerifyCode(int codeLen)
{
if (codeLen == 0)
{
codeLen = Length;
}
string[] arr = CodeSerial.Split(',');
string code = "";
int randValue = -1;
Random rand = new Random(unchecked((int)DateTime.Now.Ticks));
for (int i = 0; i < codeLen; i++)
{
randValue = rand.Next(0, arr.Length - 1);
code += arr[randValue];
}
return code;
}
public string CreateVerifyCode()
{
return CreateVerifyCode(0);
}
#endregion
}
3、编写调用网页
生成调用类文件的网页（ValidateCode.aspx），在该页面的后台代码（ValidateCode.aspx.cs文件）的Page_Load事件中写如下代码：
protected void Page_Load(object sender, EventArgs e)
{
validatedCode v = new validatedCode();
string code = v.CreateVerifyCode(); //取随机码
v.CreateImageOnPage(code, this.Context); // 输出图片
Session["CheckCode"] = code; //Session 取出验证码
}
4、判断验证结果：
Login.aspx页面的登录事件中添加验证
protected void btnLogin_Click(object sender, EventArgs e)
{
string vCode = Session["CheckCode"].ToString();
if (txtValidatedcode.Text.Trim().ToUpper() == vCode.ToUpper())
{
ScriptManager.RegisterStartupScript(this.Page, this.GetType(), "Startup", "alert('验证码正确!');", true);
}
}