JavaScript 之 使用 XMLHttpRequest 上传文件

   <div id="div1">
            <input type="file" id="uploadfile" style=" 100px; height: 25px;" />
            <input id="b1" type="button" value="上传" style="display: inline-block;  40px; height: 25px;" />
        </div>

js脚本：

https://dvcs.w3.org/hg/xhr/raw-file/tip/Overview.html

http://dev.w3.org/2006/webapi/FileAPI/

window.onload = function () {
    document.getElementById("uploadfile").addEventListener("change", function () {
        //1、获取所选的文件 暂时只选一个

        var filereader = new FileReader();
        filereader.onloadend = function (event) {
            console.log("a");
            var filedata = event.target.result;
            var request = new XMLHttpRequest();
            request.open("POST", "Handler1.ashx", true);
            var formdata = new FormData();
            formdata.append(file.name, file);
            request.send(formdata);
        }
        filereader.onloadstart = function (event) {
            console.log("b");

        }
        var file = document.getElementById("uploadfile").files[0];
        var fileblob = filereader.readAsArrayBuffer(file);
    }, true);
}

C#

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Text;
using System.IO;
using System.Data;
namespace WebApplication1
{
    /// <summary>
    /// Handler1 的摘要说明
    /// </summary>
    public class Handler1 : IHttpHandler
    {
        public byte[] buffer = null;
        public FileStream filestream = null;
        public void ProcessRequest(HttpContext context)
        {

            int length = Convert.ToInt32(context.Request.Files[0].InputStream.Length);
            buffer = new byte[length];

            //context.Request.InputStream.Read(buffer, 0, length);
            context.Request.Files[0].InputStream.Read(buffer, 0, length);

            string direcotry = System.Environment.CurrentDirectory;
            direcotry = context.Request.Path;
            direcotry = context.Request.MapPath("\");
            string filename = context.Request.Files[0].FileName;//文件名
            string hzm = filename.Substring(filename.LastIndexOf("."));//后缀名

            filestream = new FileStream(direcotry + DateTime.Now.Ticks.ToString() + hzm, FileMode.Create);
            filestream.Write(buffer, 0, buffer.Length);
            filestream.Flush();
            filestream.Close();
            context.Response.ContentType = "text/plain";
            context.Response.Write("Hello World");
        }

        public bool IsReusable
        {
            get
            {
                return false;
            }
        }
    }
}