Asp.net(C#)實現驗證碼功能

原理很簡單,就是將字母和數字放在一個數字裡面,在用隨機函式調出幾個,生成一個圖片,顯示在前臺![@more@]using System;
using System.Collections;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Web;
using System.Web.SessionState;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.HtmlControls;

namespace WebApplication2
{
///

/// ValidateCode 的摘要說明。
///

public class ValidateCode : System.Web.UI.Page
{
private void Page_Load(object sender, System.EventArgs e)
{
// 在此處放置使用者程式碼以初始化頁面
string checkCode = CreateRandomCode(4);
Session["CheckCode"]=checkCode;
CreateImage(checkCode);

}

private string CreateRandomCode(int codeCount)
{
string allChar = "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,W,X,Y,Z" ;
string[] allCharArray = allChar.Split(',');
string randomCode = "";
int temp = -1;

Random rand = new Random();
for(int i = 0; i < codeCount; i++)
{
if(temp != -1)
{
rand = new Random(i*temp*((int)DateTime.Now.Ticks));
}
int t = rand.Next(35);
if(temp == t)
{
return CreateRandomCode(codeCount);
}
temp = t;
randomCode += allCharArray[t];
}
return randomCode;
}

private void CreateImage(string checkCode)
{
int iwidth = (int)(checkCode.Length * 11.5);
System.Drawing.Bitmap image = new System.Drawing.Bitmap(iwidth, 20);
Graphics g = Graphics.FromImage(image);
Font f = new System.Drawing.Font("Arial", 10, System.Drawing.FontStyle.Bold);
Brush b = new System.Drawing.SolidBrush(Color.White);
//g.FillRectangle(new System.Drawing.SolidBrush(Color.Blue),0,0,image.Width, image.Height);
g.Clear(Color.Blue);
g.DrawString(checkCode, f, b, 3, 3);

Pen blackPen = new Pen(Color.Black, 0);
Random rand = new Random();
for (int i=0;i<5;i++)
{
int y = rand.Next(image.Height);
g.DrawLine(blackPen,0,y,image.Width,y);
}

System.IO.MemoryStream ms = new System.IO.MemoryStream();
image.Save(ms,System.Drawing.Imaging.ImageFormat.Jpeg);
Response.ClearContent();
Response.ContentType = "image/Jpeg";
Response.BinaryWrite(ms.ToArray());
g.Dispose();
image.Dispose();
}

#region Web 窗體設計器生成的程式碼
override protected void OnInit(EventArgs e)
{
//
// CODEGEN: 該呼叫是 ASP.NET Web 窗體設計器所必需的。
//
InitializeComponent();
base.OnInit(e);
}

///

/// 設計器支援所需的方法 - 不要使用程式碼編輯器修改
/// 此方法的內容。
///

private void InitializeComponent()
{
this.Load += new System.EventHandler(this.Page_Load);

}
#endregion
}
}