asp.net可刷新的驗證碼

//ValidCode.aspx.cs文件

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

public partial class ValidCode : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        Random rd = new Random(); //創建隨機數對象      

        //以下4行,產生由6個字母和數字組成的一個字符串
        string str = "ABCDEFGHIJKLMNOPQRSTURWXYZ0123456789"; //0-35
        string myValid = "";
        for (int i = 0; i < 6; i++)
        {
            myValid = myValid + str.Substring(rd.Next(35), 1);
        }
        //驗證碼值存放到Session中用來比較
        Session["Valid"] = myValid;

        //以下三句,通過隨機找一個現有圖象產生一個畫布Bitmap
        string bgFilePath = Server.MapPath(".//Images//ValidBg//bg" + new Random().Next(5) + ".jpg");//隨機找個圖象
        System.Drawing.Image imgObj = System.Drawing.Image.FromFile(bgFilePath);
        Bitmap newBitmap = new Bitmap(imgObj, 91, 25);//建立位圖對象

        Graphics g = Graphics.FromImage(newBitmap);//根據上面創建的位圖對象創建繪圖面
        SolidBrush brush = new SolidBrush(Color.Black);//設置畫筆顏色

        //定義一個含10種字體的數組
        String[] fontFamily ={ "Arial", "Verdana", "Comic Sans MS", "Impact", "Haettenschweiler", "Lucida Sans Unicode", "Garamond", "Courier New", "Book Antiqua", "Arial Narrow" };

        //通過循環,繪製每個字符,
        for (int a = 0; a < myValid.Length; a++)
        {
            Font textFont = new Font(fontFamily[rd.Next(10)], 12, FontStyle.Regular);//字體隨機,字號大小30,加粗
            //每次循環繪製一個字符,設置字體格式,畫筆顏色,字符相對畫布的X座標,字符相對畫布的Y座標
            g.DrawString(myValid.Substring(a, 1), textFont, brush, 2 + a * 15, 2);
        }

        //保存畫的圖片到輸出流中
        newBitmap.Save(Response.OutputStream, ImageFormat.Gif);
    }
}

 

 

//需要驗證碼的文件加入

<img id="imgRandom" alt="看不清？點擊更換" title="看不清？點擊更換" οnclick="ShowValidImage()" src="ValidCode.aspx?" />

<script type="text/javascript">

        function ShowValidImage() {
        var numkey = Math.random();
        document.getElementById("imgRandom").src = "ValidCode.aspx?NumKey="+numkey;
    }
</script>