//利用InputStream 属性直接从HttpPostedFile对象读取文本内容
System.IO.Stream MyStream;
int FileLen;
FileLen = file.ContentLength;
// 读取文件的 byte[]
byte[] bytes = new byte[FileLen];
MyStream = file.InputStream;
MyStream.Read(bytes, 0, FileLen);
from:http://blog.csdn.net/yyixin/article/details/5336899