網頁的驗證碼

1.首先可以寫一個產生隨機驗證碼的aspx文件，如下產生四位數字：
??? private void Page_Load(object sender, System.EventArgs e)
??? {
??????? this.CreateCheckCodeImage(GenerateCheckCode());
??? }

??? 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));
??????? //為了今后的驗證

??????? return checkCode;
??? }

??? 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 < 15; 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 < 80; 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();
??????? }
??? }
這個文件名設為CheckCode，它放在CheckCode.aspx的CheckCode.aspx.cs下就可。
2.然后在需要放驗證圖片的地方加上如下代碼：
<img src="common/CheckCode.aspx" alt=""/>就能產生驗證碼了
3.當需要取得驗證圖片值的時候可參考編寫如下代碼
if (String.Compare(Request.Cookies["CheckCode"].Value, validateTb.Text, true) != 0)
??????? {
??????????? //validateTb為文本框
??????????? validateTb.Focus();
??????????? ErrorMsg.Text = "驗證碼輸入錯誤!";
??????????? return;
??????? }

?

TraceBack：http://community.csdn.net/Expert/topic/5739/5739366.xml?temp=1.18655E-03