来源：http://www.cnblogs.com/HeroBeast/archive/2008/03/18/1084874.html
1.一般的在Asp.net里上传文件都是10m左右，要做到大文件上传，必须要改web.config,不过改了web.config有时候也上传不成功，那是每次上传的文件太大，浏览器在这个过程中会超时，采用分块上传的方法就可以避免这种情况。
2.分块上传就是利用post的方法，把数据分块上传，每块上传的数据量少，不会引起超时的问题。不说了，看代码吧。
using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.IO;
using System.Reflection;
using System.Threading;
using System.Text;
using System.Globalization;
/// <summary>
/// 实现IHttpModule接口
/// </summary>
public class HttpUploadModule : IHttpModule
{
public HttpUploadModule()
{
}
public void Init(HttpApplication application)
{
//订阅事件
application.BeginRequest += new EventHandler(this.Application_BeginRequest);
}
public void Dispose()
{
}
private void Application_BeginRequest(Object sender, EventArgs e)
{
HttpApplication app = sender as HttpApplication;
HttpWorkerRequest request = GetWorkerRequest(app.Context);
Encoding encoding = app.Context.Request.ContentEncoding;
int bytesRead = 0; // 已读数据大小
int read; // 当前读取的块的大小
int count = 8192; // 分块大小
byte[] buffer; // 保存所有上传的数据
if (request != null)
{
// 返回 HTTP 请求正文已被读取的部分。
byte[] tempBuff = request.GetPreloadedEntityBody(); //要上传的文件
// 如果是附件上传
if (tempBuff != null && IsUploadRequest(app.Request)) //判断是不是附件上传
{
// 获取上传大小
//
long length = long.Parse(request.GetKnownRequestHeader(HttpWorkerRequest.HeaderContentLength));
buffer = new byte[length];
count = tempBuff.Length; // 分块大小
// 将已上传数据复制过去
//
Buffer.BlockCopy(tempBuff, //源数据
0, //从开始读
buffer, //目标容器
bytesRead, //指定存储的开始位置
count); //要复制的字节数。
// 开始记录已上传大小
bytesRead = tempBuff.Length;
// 循环分块读取，直到所有数据读取结束
while (request.IsClientConnected() && !request.IsEntireEntityBodyIsPreloaded() && bytesRead < length)
{
// 如果最后一块大小小于分块大小，则重新分块
if (bytesRead + count > length)
{
count = (int)(length - bytesRead);
tempBuff = new byte[count];
}
// 分块读取
read = request.ReadEntityBody(tempBuff, count);
// 复制已读数据块
Buffer.BlockCopy(tempBuff, 0, buffer, bytesRead, read);
// 记录已上传大小
bytesRead += read;
}
if (request.IsClientConnected() && !request.IsEntireEntityBodyIsPreloaded())
{
// 传入已上传完的数据
InjectTextParts(request, buffer);
}
}
}
}
HttpWorkerRequest GetWorkerRequest(HttpContext context)
{
IServiceProvider provider = (IServiceProvider)HttpContext.Current;
return (HttpWorkerRequest)provider.GetService(typeof(HttpWorkerRequest));
}
/// <summary>
/// 传入已上传完的数据
/// </summary>
/// <param name="request"></param>
/// <param name="textParts"></param>
void InjectTextParts(HttpWorkerRequest request, byte[] textParts)
{
BindingFlags bindingFlags = BindingFlags.Instance | BindingFlags.NonPublic;
Type type = request.GetType();
while ((type != null) && (type.FullName != "System.Web.Hosting.ISAPIWorkerRequest"))
{
type = type.BaseType;
}
if (type != null)
{
type.GetField("_contentAvailLength", bindingFlags).SetValue(request, textParts.Length);
type.GetField("_contentTotalLength", bindingFlags).SetValue(request, textParts.Length);
type.GetField("_preloadedContent", bindingFlags).SetValue(request, textParts);
type.GetField("_preloadedContentRead", bindingFlags).SetValue(request, true);
}
}
private static bool StringStartsWithAnotherIgnoreCase(string s1, string s2)
{
return (string.Compare(s1, 0, s2, 0, s2.Length, true, CultureInfo.InvariantCulture) == 0);
}
/// <summary>
/// 是否为附件上传
/// 判断的根据是ContentType中有无multipart/form-data
/// </summary>
/// <param name="request"></param>
/// <returns></returns>
bool IsUploadRequest(HttpRequest request)
{
return StringStartsWithAnotherIgnoreCase(request.ContentType, "multipart/form-data");
}
}
3.用法
（1）修改web.config
<httpModules>
<add name="up" type="HttpUploadModule"/>
</httpModules>
<httpRuntime maxRequestLength="2000000" executionTimeout="300" />
(2)aspx
<form id="form1" runat="server" enctype="multipart/form-data">
<div>
<asp:FileUpload ID="FileUpload1" runat="server" />
<asp:Button ID="Button1" runat="server" onclick="Button1_Click" Text="Button" />
</div>
</form>
(3)aspx.cs
protected void Button1_Click(object sender, EventArgs e)
{
string strDesPath = "D:\";
string strFileName = this.FileUpload1.PostedFile.FileName;
strFileName = strDesPath + strFileName;//.Substring(strFileName.LastIndexOf("\"));
//
this.FileUpload1.PostedFile.SaveAs(strFileName);
Response.Write("文件保存到了：" + strFileName);
}
4.大文件上传的限制
虽然可以上传大文件，但是这个大小也是有限制的，不能超过2G的大小。