我正在使用这部分代码使用UpdatePanel中 imageButton 的 onClick 事件下载文件，如果我将 imageButton 添加为 updatePanel 的PostBackTrigger ，它可以正常工作，是否可以在没有完整回发的情况下做到这一点？
Dim stream As IO.Stream = Nothing
Dim bytesToRead As Integer = 10000
Dim buffer As Byte() = New Byte(bytesToRead - 1) {}
Try
Dim fileReq As Net.HttpWebRequest = CType(Net.HttpWebRequest.Create(FileURL), Net.HttpWebRequest)
Dim fileResp As Net.HttpWebResponse = CType(fileReq.GetResponse(), Net.HttpWebResponse)
If fileReq.ContentLength > 0 Then fileResp.ContentLength = fileReq.ContentLength
stream = fileResp.GetResponseStream()
Dim resp = HttpContext.Current.Response
resp.ContentType = "application/octet-stream"
resp.AddHeader("Content-Disposition", "attachment; filename=""" & FileName & """")
resp.AddHeader("Content-Length", fileResp.ContentLength.ToString())
Dim length As Integer
Do
If resp.IsClientConnected Then
length = stream.Read(buffer, 0, bytesToRead)
resp.OutputStream.Write(buffer, 0, length)
resp.Flush()
buffer = New Byte(bytesToRead - 1) {}
Else
length = -1
End If
Loop While length > 0
Finally
If stream IsNot Nothing Then
stream.Close()
End If
End Try