asp.net常用的一个很好用的控制文件下载的函数 支持续传多线（控制多线请自行修改）
可以控制文件大小 下载名称 单块数据大小 单块数据间隔 以及MIME类型 很好用
Public Shared Function ResponseFile(ByVal _Request As HttpRequest, ByVal _Response As HttpResponse, ByVal _fileName As String, ByVal _fullPath As String, ByVal BlockSize As Long, ByVal sleep As Integer, Optional ByVal MIMEType As String = "application/octet-stream") As Boolean
Try Dim myFile As New FileStream(_fullPath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite) Dim br As New BinaryReader(myFile) Try _Response.AddHeader("Accept-Ranges", "bytes") _Response.Buffer = False Dim fileLength As Long = myFile.Length Dim startBytes As Long = 0 If (Not _Request.Headers("Range") Is Nothing) Then _Response.StatusCode = 206 Dim range() As String = _Request.Headers("Range").Split("=-".ToCharArray) startBytes = Convert.ToInt64(range(1)) End If _Response.AddHeader("Content-Length", (fileLength - startBytes).ToString()) If (startBytes <> 0) Then _Response.AddHeader("Content-Range", String.Format(" bytes {0}-{1}/{2}", startBytes, fileLength - 1, fileLength)) End If _Response.AddHeader("Connection", "Keep-Alive") _Response.ContentType = MIMEType _Response.AddHeader("Content-Disposition", "attachment;filename=" + HttpUtility.UrlEncode(_fileName, System.Text.Encoding.UTF8)) br.BaseStream.Seek(startBytes, SeekOrigin.Begin) Dim maxCount As Integer = CInt(Math.Floor((fileLength - startBytes) / BlockSize) + 1) For i As Integer = 0 To maxCount - 1 If _Response.IsClientConnected Then _Response.BinaryWrite(br.ReadBytes(BlockSize)) Thread.Sleep(sleep) Else i = maxCount End If Next Catch ex As Exception Return False End Try Catch ex As Exception Return False End Try
End Function