利用HttpHandler实现验证码 及 当你希望从ashx或HttpHandler里访问你的Session时,你必须实现IReadOnlySessionState接口.

输出图片并保存验证码在Session里面。

注意：

必须继承System.Web.SessionState.IRequiresSessionState接口，才能实现Session读写！

System.Web.SessionState的一些接口

IReadOnlySessionState 指定目标 HTTP 处理程序只需要具有对会话状态值的读访问权限。这是一个标记接口，没有任何方法。

IRequiresSessionState 指定目标 HTTP 处理程序需要对会话状态值具有读写访问权。这是一个标记接口，没有任何方法。

ValidateCode.ashx---------------------------------------------------

<%@ WebHandler Language="C#" Class="ValidateCode" %>

using System;

using System.Web;

using System.Web.SessionState;

/// <summary>

/// 验证码程序

/// </summary>

public class ValidateCode : IHttpHandler, IRequiresSessionState

{

/// <summary>

/// 入口

/// </summary>

/// <param name="context"></param>

public void ProcessRequest(HttpContext context)

{

string checkCode = CreateRandomCode(4);

context.Session["Code"] = checkCode;

CreateImage(checkCode, context);

}

public bool IsReusable

{

get

{

return false;

}

}

/// <summary>

/// 产生验证码

/// </summary>

/// <param name="codeCount"></param>

/// <returns></returns>

private string CreateRandomCode(int codeCount)

{

//验证码中的出现的字符，避免了一些容易混淆的字符。

string allChar = "3,4,5,6,7,8,9,A,B,C,D,E,F,G,H,J,K,M,N,P,Q,R,S,T,U,W,X,Y";

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(allCharArray.Length);

if (temp == t)

{

return CreateRandomCode(codeCount);

}

temp = t;

randomCode += allCharArray[t];

}

return randomCode;

}

/// <summary>

/// 创建图片

/// </summary>

/// <param name="checkCode"></param>

/// <param name="context"></param>

private void CreateImage(string checkCode, HttpContext context)

{

int iwidth = (int)(checkCode.Length * 12);

System.Drawing.Bitmap image = new System.Drawing.Bitmap(iwidth, 20);

System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(image);

g.Clear(System.Drawing.Color.White);

//定义颜色

System.Drawing.Color[] c = { System.Drawing.Color.DimGray, System.Drawing.Color.DimGray, System.Drawing.Color.DimGray };

//定义字体

string[] font = { "Verdana", "Microsoft Sans Serif", "Comic Sans MS", "Arial", "宋体" };

Random rand = new Random();

//随机输出噪点

for (int i = 0; i < 50; i++)

{

int x = rand.Next(image.Width);

int y = rand.Next(image.Height);

g.DrawRectangle(new System.Drawing.Pen(System.Drawing.Color.LightGray, 0), x, y, 1, 1);

}

//输出不同字体和颜色的验证码字符

for (int i = 0; i < checkCode.Length; i++)

{

int cindex = rand.Next(3);

int findex = rand.Next(1);

System.Drawing.Font f = new System.Drawing.Font(font[findex], 10, System.Drawing.FontStyle.Bold);

System.Drawing.Brush b = new System.Drawing.SolidBrush(c[cindex]);

int ii = 4;

if ((i + 1) % 2 == 0)

{

ii = 2;

}

g.DrawString(checkCode.Substring(i, 1), f, b, 3 + (i * 10), ii);

}

//画一个边框

g.DrawRectangle(new System.Drawing.Pen(System.Drawing.Color.DarkGray, 0), 0, 0, image.Width - 1, image.Height - 1);

//输出到浏览器

System.IO.MemoryStream ms = new System.IO.MemoryStream();

image.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);

context.Response.ClearContent();

context.Response.ContentType = "image/Jpeg";

context.Response.BinaryWrite(ms.ToArray());

g.Dispose();

image.Dispose();

}

}

页面

<img src="ashx文件地址">

判断验证码是否正确

Session["Code"].ToString()==输入的字符

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当你希望从ashx或HttpHandler里访问你的Session时,你必须实现IReadOnlySessionState接口.






当你希望从ashx或HttpHandler里访问你的Session时,你必须实现IReadOnlySessionState接口.

代码:

using System;

using System.Web;

using System.Web.SessionState;

public class DownloadHandler : IHttpHandler, IReadOnlySessionState

{

public bool IsReusable { get { return true; } }

public void ProcessRequest(HttpContext ctx)

{

ctx.Response.Write(ctx.Session["fred"]);

}

}