ASP.NET提供文件下载函数（支持大文件、续传、速度限制、资源占用小）VB.NET版
时间：2008/10/4 10:56:54
阅读：6486
''' <summary>
''' ASP.NET提供文件下载函数（支持大文件、续传、速度限制、资源占用小）
''' </summary>
''' <param name="_Request">Page.Request对象</param>
''' <param name="_Response">Page.Response对象</param>
''' <param name="_fileName">下载文件名</param>
''' <param name="_fullPath">带文件名下载路径</param>
''' <param name="_speed">每秒允许下载的字节数</param>
''' <returns>返回是否成功</returns>
''' <remarks>
''' '输出硬盘文件，提供下载 调用例
'''</remarks>
Public Shared Function ResponseFile()Function ResponseFile(ByVal _Request As HttpRequest, ByVal _Response As HttpResponse, ByVal _fileName As String, ByVal _fullPath As String, ByVal _speed As Long) As Boolean
Try
Dim myFile As New System.IO.FileStream(_fullPath, System.IO.FileMode.Open, System.IO.FileAccess.Read, System.IO.FileShare.ReadWrite)
Dim br As New System.IO.BinaryReader(myFile)
Try
_Response.AddHeader("Accept-Ranges", "bytes")
_Response.Buffer = False
Dim fileLength As Long = myFile.Length
Dim startBytes As Long = 0
Dim pack As Integer = 10240
'10K bytes
'int sleep = 200; //每秒5次 即5*10K bytes每秒
Dim sleep As Integer = CInt(Math.Floor(1000 * pack / _speed)) + 1
If _Request.Headers("Range") IsNot Nothing Then
_Response.StatusCode = 206
Dim range As String() = _Request.Headers("Range").Split(New Char() {"="c, "-"c})
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 = "application/octet-stream"
_Response.AddHeader("Content-Disposition", "attachment;filename=" + HttpUtility.UrlEncode(_fileName, System.Text.Encoding.UTF8))
br.BaseStream.Seek(startBytes, System.IO.SeekOrigin.Begin)
Dim maxCount As Integer = CInt(Math.Floor((fileLength - startBytes) / pack)) + 1
For i As Integer = 0 To maxCount - 1
If _Response.IsClientConnected Then
_Response.BinaryWrite(br.ReadBytes(pack))
System.Threading.Thread.Sleep(sleep)
Else
i = maxCount
End If
Next
Catch
Return False
Finally
br.Close()
myFile.Close()
End Try
Catch
Return False
End Try
Return True
End Function
调用实例：
Page.Response.Clear()
Dim success As Boolean = ResponseFile(Page.Request,Page.Response,"filename","C:\download.date",1024000)
If Not success Then
Response.Write("下载文件出错！")
End If
Page.Response.End()