产生验证码。

方法一

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.Design;
public partial class image : System.Web.UI.Page
{
    private void Page_Load(object sender, System.EventArgs e)
    {
        //如果要在页面a.aspx生成验证码，则在该页面添加一个图片控件，假设命名为：Image1，然后在page_Load事件中写如下代码：
        //ImageButton1.ImageUrl = "ValidateCode.aspx";
        //这样就可以生成验证码了，ValidateCode.aspx页面可以随便放在哪里，不过要注意Image1.src 要写对，同级可以直接写ValidateCode.aspx，上一级写../ValidateCode.aspx，很方便吧。

        if (!IsPostBack)
        {
            //RndNum是一个自定义函数
            //这里的数字4代表显示的是4位的验证字符串！
            //string VNum=RndNum(4);
            string VNum = GenerateRandom(6);
            Session["VNum"] = VNum;
            Validate_Code(VNum);
        }
    }
    private void Validate_Code(string VNum)
    {
        int Gheight = (int)(VNum.Length * 10);
        //gheight为图片宽度,根据字符长度自动更改图片宽度
        System.Drawing.Bitmap Img = new System.Drawing.Bitmap(Gheight, 20);
        System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(Img);
        g.DrawString(VNum, new System.Drawing.Font("Dotum", 10), new System.Drawing.SolidBrush(System.Drawing.Color.Red), 3, 3);
        //在矩形内绘制字串（字串，字体，画笔颜色，左上x.左上y）
        System.IO.MemoryStream ms = new System.IO.MemoryStream();
        Img.Save(ms, System.Drawing.Imaging.ImageFormat.Png);
        Response.ClearContent(); //需要输出图象信息
        Response.ContentType = "image/Png";
        Response.BinaryWrite(ms.ToArray());
        g.Dispose();
        Img.Dispose();
        Response.End();
    }
    private static 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',
        };
    public static string GenerateRandom(int Length)
    {
        System.Text.StringBuilder newRandom = new System.Text.StringBuilder(36);
        Random rd = new Random();
        for (int i = 0; i < Length; i++)
        {
            newRandom.Append(constant[rd.Next(36)]);
        }
        return newRandom.ToString();
    }
}

方法二

 

 

using System;
using System.Collections;
using System.Configuration;
using System.Data;
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.Drawing;

public partial class CheckCode : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        CreateCheckCodeImage(GenerateCheckCode());
    }

    /// <summary>
    /// 生成验证码
    /// </summary>
    /// <returns></returns>
    private string GenerateCheckCode()
    {
        int number;
        char code;
        string checkCode = String.Empty;

        System.Random random = new Random();
        for (int i = 0; i < 4; i++)
        {
            number = random.Next();
            code = (char)('0' + (char)(number % 10));
            checkCode += code.ToString();
        }
       
        Response.Cookies.Add(new HttpCookie("CheckCode", checkCode));
        return checkCode;
    }

    /// <summary>
    /// 创建验证图片
    /// </summary>
    /// <param name="checkCode"></param>
    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 < 100; 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.AliceBlue), x1, y1, x2, y2);
            }

            Font font = new System.Drawing.Font("Arial", 13, (System.Drawing.FontStyle.Bold | System.Drawing.FontStyle.Regular));
            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();
        }
    }
}

 方法一怎么没有背景图片呀！谁能帮我修改一下！