第一步生成驗證碼

新增一個validatecode.aspx頁面

在validatecode.aspx.cs的代碼如下

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;
using system.drawing.imaging;

public partial class validatecode : system.web.ui.page
{   //該頁面將用于生成驗證碼圖片
    protected void page_load(object sender, eventargs e)
    {     //調用函數將驗證碼生成圖片
        this.createcheckcodeimage(generatecheckcode());
      
    }
    private string generatecheckcode()
    {  //產生五位的隨機字符串
        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));
       session["checkcode"] = checkcode;//用于客戶端校驗碼比較

        return checkcode;
    }

    private void createcheckcodeimage(string checkcode)
    {  //將驗證碼生成圖片顯示
        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
        {
            //生成隨機生成器
            random random = new random();

            //清空圖片背景色
            g.clear(color.white);

            //畫圖片的背景噪音線
            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);

            //畫圖片的前景噪音點
            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()));
            }

            //畫圖片的邊框線
            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();
        }
    }
}

第二步測試驗證碼

建立test.aspx

form id="form1" runat="server">
    <div>
       
        <asp:textbox id="textbox1" runat="server"></asp:textbox>
        <asp:button id="button1" runat="server" text="button" onclick="button1_click" /><br />
        &nbsp;
        <asp:image id="image1" runat="server" imageurl="~/validatecode.aspx" />//該圖片將用于顯示驗證碼
        </div>
    </form>

test.aspx.cs代碼

protected void page_load(object sender, eventargs e)
    {
       
    }
    protected void button1_click(object sender, eventargs e)
    {
       
      if (this.textbox1.text.tostring().trim() == session["checkcode"].tostring()) { response.write("<script lauguage='javascript'>alert('驗證成功');</script>"); }
        }