上传大文件，有好几种方法：
1、思归的HttpWorkerRequest方法，
2、利用第三方的控件 AspNetUpload
3、修改web.config文件，但是不能捕获错误。
4、通过ftp的方式上传。服务器需要提供ftp服务。
通过第3种方式：
修改Webcong文件:
<system.web>
<httpRuntime maxRequestLength="40690"
useFullyQualifiedRedirectUrl="true"
executionTimeout="6000"
useFullyQualifiedRedirectUrl="false"
minFreeThreads="8"
minLocalRequestFreeThreads="4"
appRequestQueueLimit="100"
enableVersionHeader="true"
/>
</system.web>
其中与上传有密切关系的是：
maxRequestLength
指示 ASP.NET 支持的最大文件上载大小。
该限制可用于防止因用户将大量文件传递到该服务器而导致的拒绝服务攻击。
指定的大小以 KB 为单位。
默认值为 4096 KB (4 MB)。
executionTimeout
指示在被 ASP.NET 自动关闭前，允许执行请求的最大秒数。
单位为秒，在上传大的文件时把这个设的大一些。
如果服务器内存512M,已可上传大小160M的文件。(没试过，csdn上众帖子的一致意见。)
到这里web.config的设置就已经结束。
可是一旦上传文件的大小超过了这个设置的文件大小范围就会发生如下错误：
该页无法显示
您要查看的页当前不可用。网站可能遇到
一下也是转载内容，有代码和讲解！
这次在项目中，用到了大文件上传，要上传的文件有100多m，于是研究现在国内使用的大文件上传的
组件发现用的比较多的有两个控件AspnetUpload 2.0和Lion.Web.UpLoadModule，另外还有思归在它的博客
堂中所说的办法 http://blog.joycode.com/saucer/archive/2004/03/16/16225.aspx
两个控件的方法是：利用隐含的HttpWorkerRequest，用它的GetPreloadedEntityBody 和 ReadEntityBody方法从IIS为ASP.NET建立的pipe里分块读取数据。Chris Hynes为我们提供了这样的一个方案(用HttpModule)，该方案除了允许你上传大文件外，还能实时显示上传进度。
Lion.Web.UpLoadModule和AspnetUpload 两个.NET组件都是利用的这个方案。
当上传单文件时，两个软件的方法是一样的，继承HttpModule
HttpApplication application1 = sender as HttpApplication;
HttpWorkerRequest request1 = (HttpWorkerRequest) ((IServiceProvider) HttpContext.Current).GetService(typeof(HttpWorkerRequest));
try
{
if (application1.Context.Request.ContentType.IndexOf("multipart/form-data") <= -1)
{
return;
}
//Check The HasEntityBody
if (!request1.HasEntityBody())
{
return;
}
int num1 = 0;
TimeSpan span1 = DateTime.Now.Subtract(this.beginTime);
string text1 = application1.Context.Request.ContentType.ToLower();
byte[] buffer1 = Encoding.ASCII.GetBytes(("\r\n--" + text1.Substring(text1.IndexOf("boundary=") + 9)).ToCharArray());
int num2 = Convert.ToInt32(request1.GetKnownRequestHeader(11));
Progress progress1 = new Progress();
application1.Context.Items.Add("FileList", new Hashtable());
byte[] buffer2 = request1.GetPreloadedEntityBody();
num1 += buffer2.Length;
string text2 = this.AnalysePreloadedEntityBody(buffer2, "UploadGUID");
if (text2 != string.Empty)
{
application1.Context.Items.Add("LionSky_UpLoadModule_UploadGUID", text2);
}
bool flag1 = true;
if ((num2 > this.UpLoadFileLength()) && ((0 > span1.TotalHours) || (span1.TotalHours > 3)))
{
flag1 = false;
}
if ((0 > span1.TotalHours) || (span1.TotalHours > 3))
{
flag1 = false;
}
string text3 = this.AnalysePreloadedEntityBody(buffer2, "UploadFolder");
ArrayList list1 = new ArrayList();
RequestStream stream1 = new RequestStream(buffer2, buffer1, null, RequestStream.FileStatus.Close, RequestStream.ReadStatus.NoRead, text3, flag1, application1.Context, string.Empty);
list1.AddRange(stream1.ReadBody);
if (text2 != string.Empty)
{
progress1.FileLength = num2;
progress1.ReceivedLength = num1;
progress1.FileName = stream1.OriginalFileName;
progress1.FileCount = ((Hashtable) application1.Context.Items["FileList"]).Count;
application1.Application["_UploadGUID_" + text2] = progress1;
}
if (!request1.IsEntireEntityBodyIsPreloaded())
{
byte[] buffer4;
ArrayList list2;
int num3 = 204800;
byte[] buffer3 = new byte[num3];
while ((num2 - num1) >= num3)
{
if (!application1.Context.Response.IsClientConnected)
{
this.ClearApplication(application1);
}
num3 = request1.ReadEntityBody(buffer3, buffer3.Length);
num1 += num3;
list2 = stream1.ContentBody;
if (list2.Count > 0)
{
buffer4 = new byte[list2.Count + buffer3.Length];
list2.CopyTo(buffer4, 0);
buffer3.CopyTo(buffer4, list2.Count);
stream1 = new RequestStream(buffer4, buffer1, stream1.FileStream, stream1.FStatus, stream1.RStatus, text3, flag1, application1.Context, stream1.OriginalFileName);
}
else
{
stream1 = new RequestStream(buffer3, buffer1, stream1.FileStream, stream1.FStatus, stream1.RStatus, text3, flag1, application1.Context, stream1.OriginalFileName);
}
list1.AddRange(stream1.ReadBody);
if (text2 != string.Empty)
{
progress1.ReceivedLength = num1;
progress1.FileName = stream1.OriginalFileName;
progress1.FileCount = ((Hashtable) application1.Context.Items["FileList"]).Count;
application1.Application["_UploadGUID_" + text2] = progress1;
}
}
buffer3 = new byte[num2 - num1];
if (!application1.Context.Response.IsClientConnected && (stream1.FStatus == RequestStream.FileStatus.Open))
{
this.ClearApplication(application1);
}
num3 = request1.ReadEntityBody(buffer3, buffer3.Length);
list2 = stream1.ContentBody;
if (list2.Count > 0)
{
buffer4 = new byte[list2.Count + buffer3.Length];
list2.CopyTo(buffer4, 0);
buffer3.CopyTo(buffer4, list2.Count);
stream1 = new RequestStream(buffer4, buffer1, stream1.FileStream, stream1.FStatus, stream1.RStatus, text3, flag1, application1.Context, stream1.OriginalFileName);
}
else
{
stream1 = new RequestStream(buffer3, buffer1, stream1.FileStream, stream1.FStatus, stream1.RStatus, text3, flag1, application1.Context, stream1.OriginalFileName);
}
list1.AddRange(stream1.ReadBody);
if (text2 != string.Empty)
{
progress1.ReceivedLength = num1 + buffer3.Length;
progress1.FileName = stream1.OriginalFileName;
progress1.FileCount = ((Hashtable) application1.Context.Items["FileList"]).Count;
if (flag1)
{
progress1.UploadStatus = Progress.UploadStatusEnum.Uploaded;
}
else
{
application1.Application.Remove("_UploadGUID_" + text2);
}
}
}
byte[] buffer5 = new byte[list1.Count];
list1.CopyTo(buffer5);
this.PopulateRequestData(request1, buffer5);
}
catch (Exception exception1)
{
this.ClearApplication(application1);
throw exception1;
}
而思归所说的方法使用Mime也能上传大文件，在以下地址下载
http://krystalware.com/files/slickupload.zip
不过觉得的思归的方法容易很多
相关文章：
让asp.net默认的上传组件支持进度条反映
http://blog.joycode.com/dotey/archive/2005/06/12/53557.aspx // 宝玉
http://blog.joycode.com/saucer/archive/2004/03/16/16225.aspx // 思归
http://www.cnblogs.com/bestcomy/archive/2004/06/09/14267.aspx // bestcomy
http://krystalware.com/wiki/default.aspx/KrystalWiki.UploadSpike1
http://www.blueidea.com/tech/program/2005/2997.asp //ftp
通过Web Services上传和下载文件
http://dotnet.aspx.cc/ShowDetail.aspx?id=6381BD5F-51F3-4339-4239-1328564A1B2A
上传组件是如何不受settimeout限制的？
http://www.ietf.org/rfc/rfc1867.txt?number=1867
下载
http://support.microsoft.com/default.aspx?scid=kb;en-us;812406&Product=aspnet
上传源代码下载：
openlabupload.rar
