Asp.net(c#)实现多线程断点续传 
http://www.cnblogs.com/bestcomy/archive/2004/08/10/31950.html
以前一直错误的认为在ASP.NET中无法通过编程方式实现多线程断点续传，今天终于获得了这样一个解决方案，让我明白要学习的东西还很多
。
此解决方案基于其它解决方案及相关资料，根据我自己的理解改进.如有错漏，请尽管指出
;如有其它更好的解决方案，请推荐一下，感谢先。
System.IO.Stream iStream = null;
// Buffer to read 10K bytes in chunk:
byte[] buffer = new Byte[10240];
// Length of the file:
int length;
// Total bytes to read:
long dataToRead;
// Identify the file to download including its path.
string filepath = @"E:/software/SQL Server 2000 Personal Edition.ISO";
// Identify the file name.
string filename = System.IO.Path.GetFileName(filepath);
try
{
// Open the file.
iStream = new System.IO.FileStream(filepath, System.IO.FileMode.Open,
System.IO.FileAccess.Read,System.IO.FileShare.Read);
Response.Clear();
// Total bytes to read:
dataToRead = iStream.Length;
long p = 0;
if(Request.Headers["Range"]!=null)
{
Response.StatusCode = 206;
p = long.Parse( Request.Headers["Range"].Replace("bytes=","").Replace("-",""));
}
if(p != 0)
{
Response.AddHeader("Content-Range","bytes " + p.ToString() + "-" + ((long)(dataToRead - 1)).ToString() + "/" + dataToRead.ToString());
}
Response.AddHeader("Content-Length",((long)(dataToRead-p)).ToString());
Response.ContentType = "application/octet-stream";
Response.AddHeader("Content-Disposition", "attachment; filename=" + System.Web.HttpUtility.UrlEncode(Request.ContentEncoding.GetBytes(filename)));
iStream.Position = p;
dataToRead = dataToRead - p;
// Read the bytes.
while (dataToRead > 0)
{
// Verify that the client is connected.
if (Response.IsClientConnected)
{
// Read the data in buffer.
length = iStream.Read(buffer, 0, 10240);
// Write the data to the current output stream.
Response.OutputStream.Write(buffer, 0, length);
// Flush the data to the HTML output.
Response.Flush();
buffer= new Byte[10240];
dataToRead = dataToRead - length;
}
else
{
//prevent infinite loop if user disconnects
dataToRead = -1;
}
}
}
catch (Exception ex)
{
// Trap the error, if any.
Response.Write("Error : " + ex.Message);
}
finally
{
if (iStream != null)
{
//Close the file.
iStream.Close();
}
Response.End();
}