asp.net 在ashx文件中读写session

首先要继承 System.Web.SessionState.IReadOnlySessionState 的接口
其中：System.Web.SessionState.IReadOnlySessionState为只读会话的接口

而：System.Web.SessionState.IRequiresSessionState 为可读可写会话的接口

View Code
using System;
  using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Drawing;
using System.Web.UI.WebControls;
using System.Web.SessionState;
namespace CanYou.FinancePlat.Web
{
     /// <summary>
     /// GeneraLoginCode 的摘要说明
     /// </summary>
     public class GeneraLoginCode : IHttpHandler, IRequiresSessionState
     {
         public void ProcessRequest(HttpContext context)
         {
             string checkCode = CreateCode(4);
             context.Response.Cache.SetCacheability(HttpCacheability.NoCache);
             context.Session["_Login_ValidateCode"] = checkCode;
             CreateImage(checkCode, context);
         }
         private string CreateCode(int codeLength)
         {
             string so = "1,2,3,4,5,6,7,8,9,0,a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z,A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z";
             string[] strArr = so.Split(',');
             string code = "";
             Random rand = new Random();
             for (int i = 0; i < codeLength; i++)
             {
                 code += strArr[rand.Next(0, strArr.Length)];
             }
             return code;
         }
         private void CreateImage(string code, HttpContext context)
         {
             Bitmap image = new Bitmap(60, 20);
             Graphics g = Graphics.FromImage(image);
             WebColorConverter ww = new WebColorConverter();
             g.Clear((Color)ww.ConvertFromString("#FAE264"));
             Random random = new Random();
             //画图片的背景噪音线
             for (int i = 0; i < 12; 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.LightGray), x1, y1, x2, y2);
             }
             Font font = new Font("Arial", 15, FontStyle.Bold | FontStyle.Italic);
             System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(
                 new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.Gray, 1.2f, true);
             g.DrawString(code, font, brush, 0, 0);
             //画图片的前景噪音点
             for (int i = 0; i < 10; i++)
             {
                 int x = random.Next(image.Width);
                 int y = random.Next(image.Height);
                 image.SetPixel(x, y, Color.White);
             }
             //画图片的边框线
             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);
             context.Response.ClearContent();
             context.Response.ContentType = "image/Gif";
             context.Response.BinaryWrite(ms.ToArray());
             g.Dispose();
             image.Dispose();
         }
         public bool IsReusable
         {
             get
             {
                 return false;
             }
         }
     }
}