验证码图片生成代码

using System.Drawing;

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

    //生成随机数
    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();

            if (number % 2 == 0)
                code = (char)(0 + (char)(number % 10));
            else
                code = (char)(0 + (char)(number % 10));
            //code = (char)(a + (char)(number % 26));

            checkCode += code.ToString();
        }

        Response.Cookies.Add(new HttpCookie("CheckCode", checkCode));

        //将生成的随机数保存到session中

        Session["Num"] = checkCode.ToString().ToLower();

        return checkCode;
    }

    private void CreateCheckCodeImage(string checkCode)
    {
        if (checkCode == null || checkCode.Trim() == String.Empty)
            retu

补充：软件开发 , C# ,