使用C#语言生成验证码

首先先 添加一个页面 ，命名为 code.aspx
添加命名空间

using System.IO;
using System.Drawing.Imaging;
using System.Drawing.Drawing2D;
using System.Drawing;

添加页面初始化的 部分

protected void Page_Load(object sender, EventArgs e)
{
    //先产生数字串
    string Code = this.CreateRandomCode(4);
    //用session保存
    Session["CheckCode"] = Code;
    //作图
    CreateImage(Code);
}

上面代码中的CreateRandomCode是用来生成指定位数的随机数，CreateImage是绘制图案，下面看一下这两个方法：

CreateRandomCode代码：

public string CreateRandomCode(int codeCount)
{
    string allChar = "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";
    string[] allCharArray = allChar.Split(',');
    string randomCode = "";
    int temp = -1;
    Random rand = new Random();
    for (int i = 0; i < codeCount; i++)
    {
        if (temp != -1)
        {
            rand = new Random(i * temp * ((int)DateTime.Now.Ticks));
        }
        int t = rand.Next(36);
        if (temp != -1 && temp == t)
        {
            return CreateRandomCode(codeCount);
        }
        temp = t;
        randomCode += allCharArray[t];
    }
    return randomCode;
}

CreateImage代码：

private void CreateImage(string checkCode)
{
    int iwidth = (int)(checkCode.Length * 15);
    System.Drawing.Bitmap image = new System.Drawing.Bitmap(iwidth, 25);
    Graphics g = Graphics.FromImage(image);
    g.Clear(Color.White);
    //定义颜色
    Color[] c = { Color.Black, Color.Red, Color.DarkBlue, Color.Green, Color.Orange, Color.Brown, Color.DarkCyan, Color.Purple };
    //定义字体
    string[] font = { "Verdana", "Microsoft Sans Serif", "Comic Sans MS", "Arial", "宋体" };
    Random rand = new Random();
    //随机输出噪点
    for (int i = 0; i < 50; i++)
    {
        int x = rand.Next(image.Width);
        int y = rand.Next(image.Height);
        g.DrawRectangle(new Pen(Color.LightGray, 0), x, y, 1, 1);
    }
    //输出不同字体和颜色的验证码字符
    for (int i = 0; i < checkCode.Length; i++)
    {
        int cindex = rand.Next(7);
        int findex = rand.Next(5);
        Font f = new System.Drawing.Font(font[findex], 10, System.Drawing.FontStyle.Bold);
        Brush b = new System.Drawing.SolidBrush(c[cindex]);
        int ii = 4;
        if ((i + 1) % 2 == 0)
        {
            ii = 2;
        }
        g.DrawString(checkCode.Substring(i, 1), f, b, 3 + (i * 12), ii);
    }
    //画一个边框
    g.DrawRectangle(new Pen(Color.Black, 0), 0, 0, image.Width - 1, image.Height - 1);
    //输出到浏览器
    System.IO.MemoryStream ms = new System.IO.MemoryStream();
    image.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
    Response.ClearContent();
    Response.C;
    Response.BinaryWrite(ms.ToArray());
    g.Dispose();
    image.Dispose();
}

下面贴出完整的代码

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.IO;
using System.Drawing.Imaging;
using System.Drawing.Drawing2D;
using System.Drawing;
public partial class code : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        //先产生数字串
        string Code = this.CreateRandomCode(4);
        //用session保存
        Session["CheckCode"] = Code;
        //作图
        CreateImage(Code);
    }
    private void CreateImage(string checkCode)
    {
        int iwidth = (int)(checkCode.Length * 15);
        System.Drawing.Bitmap image = new System.Drawing.Bitmap(iwidth, 25);
        Graphics g = Graphics.FromImage(image);
        g.Clear(Color.White);
        //定义颜色
        Color[] c = { Color.Black, Color.Red, Color.DarkBlue, Color.Green, Color.Orange, Color.Brown, Color.DarkCyan, Color.Purple };
        //定义字体
        string[] font = { "Verdana", "Microsoft Sans Serif", "Comic Sans MS", "Arial", "宋体" };
        Random rand = new Random();
        //随机输出噪点
        for (int i = 0; i < 50; i++)
        {
            int x = rand.Next(image.Width);
            int y = rand.Next(image.Height);
            g.DrawRectangle(new Pen(Color.LightGray, 0), x, y, 1, 1);
        }
        //输出不同字体和颜色的验证码字符
        for (int i = 0; i < checkCode.Length; i++)
        {
            int cindex = rand.Next(7);
            int findex = rand.Next(5);
            Font f = new System.Drawing.Font(font[findex], 10, System.Drawing.FontStyle.Bold);
            Brush b = new System.Drawing.SolidBrush(c[cindex]);
            int ii = 4;
            if ((i + 1) % 2 == 0)
            {
                ii = 2;
            }
            g.DrawString(checkCode.Substring(i, 1), f, b, 3 + (i * 12), ii);
        }
        //画一个边框
        g.DrawRectangle(new Pen(Color.Black, 0), 0, 0, image.Width - 1, image.Height - 1);
        //输出到浏览器
        System.IO.MemoryStream ms = new System.IO.MemoryStream();
        image.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
        Response.ClearContent();
        Response.C;
        Response.BinaryWrite(ms.ToArray());
        g.Dispose();
        image.Dispose();
    }
    public string CreateRandomCode(int codeCount)
    {
        string allChar = "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";
        string[] allCharArray = allChar.Split(',');
        string randomCode = "";
        int temp = -1;
        Random rand = new Random();
        for (int i = 0; i < codeCount; i++)
        {
            if (temp != -1)
            {
                rand = new Random(i * temp * ((int)DateTime.Now.Ticks));
            }
            int t = rand.Next(36);
            if (temp != -1 && temp == t)
            {
                return CreateRandomCode(codeCount);
            }
            temp = t;
            randomCode += allCharArray[t];
        }
        return randomCode;
    }
}