我正在开发一个应用程序（在 C# 中）。这基本上是一个文件上传/下载应用程序（就像 filezila）。
但是有一个特殊功能（文件下载）：-
我们可以将文件分成不同的段（最多 100 个）。并且可以通过各种循环重复这个过程（意味着我们可以将一个文件分成不同的段，并且可以重复这个过程不止一次（通过循环），同时）。
我为此使用线程概念。在应用程序中，有一些进度条和标签显示上传/下载状态。
我的问题是：-
如果我为更多数字执行此过程（下载），例如：-
100 个周期和（周期可以超过 100 个）
100 段
意味着我们将一个文件分成 100 个部分（段），并且相同的过程将工作 100 次（周期）。
意味着 100 * 100 =10,000 个文件将通过同一进程同时下载。
但是我面临的问题是，如果我为这项任务采取大量数字，那么应该会打开更多线程。
如果有 100 个 TCP 端口/线程同时运行，应用程序将挂起。
我为此尝试了很多东西，但我还没有成功。就像 -
异步委托、线程池等
我在更新进度条和标签时遇到了一个主要问题（因为当前的功能正在使用异步委托）。
请建议我一些方法来解决这个问题。
因为所有这些线程都想将数据传递给 UI 线程以显示进度，所以 UI 线程正在成为您应用程序的瓶颈。
您可以添加一个计时器，该计时器不时导致 UI 线程检查作业的进度。
这样，UI 线程不是由大量线程驱动，而是由时间驱动。
如果您需要更多详细信息，请发布一些代码。
你好 Erno 我正在发送一些代码以便更好地理解：-
这是下载功能：
Public Sub FileDownload()
txtBytesToDownload.Text = totalBytesToDownload.ToString("N", nfi) 'set textbox with total file size
del = New MyDelegate(AddressOf DownloadDataInRange)
callback = New AsyncCallback(AddressOf CalcCallback)
TotalBytesToDownloadForEachCycle = totalBytesToDownload
downloadedBytes = 0
dlStopWatch = Stopwatch.StartNew()
Dim flag As Integer = 0
Dim segment As Integer = nuSegment.Value 'total segments
Dim cyl = cycleNumericUpDown.Value 'total cycles
'ServicePointManager.DefaultConnectionLimit = segment
If UtilityFunctions.CheckRangeSupported(dlUrlHttpTextBox.Text) Then
Dim segmentSize As Integer = 0
segmentSize = TotalBytesToDownloadForEachCycle / segment
' For cy As Integer = 0 To (cyl - 1)
For ctr As Integer = 0 To (segment - 1) 'loop for total Segments
GC.Collect()
flag += 1
Dim fileValues As New FileValues()
If ctr = 0 Then
fileValues.StartPoint = 0 'starting point of each segment (in bytes)
Else
fileValues.StartPoint = segmentSize * ctr + 1
End If
fileValues.EndPoint = fileValues.StartPoint + segmentSize 'end point of each segment (in bytes)
If (ctr = (segment - 1)) Then
fileValues.EndPoint += TotalBytesToDownloadForEachCycle Mod segment
End If
fileValues.URL = dlUrlHttpTextBox.Text 'downloading file url
Dim str As String = ctr.ToString() + "_" + flag.ToString()
' del.BeginInvoke(fileValues, callback, Nothing)
newThread = New System.Threading.Thread(AddressOf DownloadBytes) 'Thread starts here
newThread.Priority = ThreadPriority.Highest
newThread.IsBackground = True
newThread.Start(fileValues)
'ThreadPool.QueueUserWorkItem(AddressOf DownloadBytes, fileValues)
fileValues = Nothing
Next
' ProgressBarTotal.Value += 1
' Next
Else
Dim fileValues As New FileValues()
fileValues.StartPoint = 0
fileValues.EndPoint = TotalBytesToDownloadForEachCycle
fileValues.URL = dlUrlHttpTextBox.Text
Dim newThread As New System.Threading.Thread(AddressOf DownloadBytes)
newThread.Name = "Thread1"
newThread.Start(fileValues)
'ThreadPool.QueueUserWorkItem(AddressOf DownloadBytes, fileValues)
fileValues = Nothing
End If
Console.WriteLine("Http Downloload End")
Debug.Print("thread List 1 count =" + _threadsList1.Count.ToString() + ", thread list 2 count =" + _threadsList2.Count.ToString() + ", thread list 3 count =" + _threadsList3.Count.ToString())
'MessageBox.Show("finished - flag=" + flag.ToString())
'After all Cycles Complete
'startButton.Enabled = True
'abortButton.Enabled = False
'skipButton.Enabled = False
'DataGridViewDLOrPing.Enabled = True
'DataGridViewUL.Enabled = True
'protocolComboBox.Enabled = True
'modelComboBox.Enabled = True
'testTypeComboBox.Enabled = True
'measurementComboBox.Enabled = True
'cycleNumericUpDown.Enabled = True
'DelayNumericUpDown.Enabled = True
'InputBoxPrivilege()
End Sub
这是 Thread 将调用以读取字节的函数：
Public Sub DownloadBytes(ByVal p_fileValues As FileValues)
Dim httpWebRequest As HttpWebRequest
Dim httpWebResponse As HttpWebResponse
Dim responseStream As Stream
Dim threadName = threadID
Try
Console.WriteLine("Start " + Thread.CurrentThread.Name)
httpWebRequest = DirectCast(WebRequest.Create(p_fileValues.URL), HttpWebRequest)
'httpWebRequest.ProtocolVersion = HttpVersion.Version11
httpWebRequest.KeepAlive = False
httpWebRequest.AddRange(p_fileValues.StartPoint, p_fileValues.EndPoint)
httpWebRequest.Credentials = CredentialCache.DefaultCredentials
httpWebRequest.Proxy = WebRequest.DefaultWebProxy
httpWebResponse = CType(httpWebRequest.GetResponse(), HttpWebResponse)
responseStream = httpWebResponse.GetResponseStream()
Dim bytesSize As Integer = 0
' A buffer for storing and writing the data retrieved from the server
Dim downBuffer As Byte() = New Byte(2047) {}
Dim bytesAlreadyDownloaded As Int64 = p_fileValues.StartPoint
' Loop through the buffer until the buffer is empty
While (True)
'end while loop if the Abort button is clicked
If (isActionAborted = True) Then
Exit While
End If
'currentCycle is > total Cycles ,then end while
If (currentCycleDownload > cycleNumericUpDown.Value) Then
Exit While
End If
bytesSize = responseStream.Read(downBuffer, 0, downBuffer.Length)
bytesAlreadyDownloaded += bytesSize
'speedtimer.Start()
If (bytesSize <= 0) Then
If (downloadedBytes < totalBytesToDownload) Then
Me.Invoke(New UploadProgressCallback(AddressOf Me.UpdateDownloadProgress), New Object() {(totalBytesToDownload - downloadedBytes), totalBytesToDownload})
End If
Exit While
End If
' Invoke the method that updates the form's label and progress bar
Me.Invoke(New DownloadProgressCallback(AddressOf Me.UpdateDownloadProgress), New Object() {bytesSize, TotalBytesToDownloadForEachCycle})
If (bytesAlreadyDownloaded > p_fileValues.EndPoint) Then
'Console.WriteLine("Downloading part files Exit " + p_fileValues.StartPoint.ToString() + "," + p_fileValues.EndPoint.ToString())
Exit While
End If
End While
responseStream.Flush()
responseStream.Close()
httpWebResponse.Close()
responseStream.Dispose()
responseStream = Nothing
httpWebResponse = Nothing
Console.WriteLine("End " + Thread.CurrentThread.Name)
'ProgressDownload.Value = Convert.ToInt32((downloadedBytes * 100) / totalBytesToDownload)
' downloadedBytesTextBox.Text = downloadedBytes.ToString("N", nfi)
Catch ex As Exception
Console.WriteLine("Error " + Thread.CurrentThread.Name)
Console.WriteLine(ex)
Finally
Console.WriteLine("Finally " + Thread.CurrentThread.Name)
GC.Collect()
' GC.WaitForPendingFinalizers()
'newThread.Abort()
'Try
'Thread.CurrentThread.Abort()
'Catch ex1 As Exception
'End Try
End Try
'Return 1
End Sub
此功能将更新进度条和表单上的其他标签：
Private Sub UpdateDownloadProgress(ByVal BytesRead As Int64, ByVal TotalBytes As Int64)
If Not swDL Is Nothing AndAlso swDL.IsRunning Then
swDL.Stop()
If swDL.ElapsedMilliseconds > 0 Then
resultGrid.Rows.Item(HandoverGridCounter - 1).Cells(4).Value &= "DL: " & swDL.ElapsedMilliseconds & " ms"
End If
swDL = Nothing
End If
If (dlCurrentspeed > 0) Then
'txtCurrentSpeedDL.Text = Math.Round((dlCurrentspeed / 1024), 0) & " KB/s"
End If
downloadedBytes += BytesRead
If downloadedBytes >= totalBytesToDownload Then
downloadedBytes = totalBytesToDownload
End If
ProgressDownload.Value = Convert.ToInt32((downloadedBytes * 100) / TotalBytes)
downloadedBytesTextBox.Text = downloadedBytes.ToString("N", nfi) ' & " bytes"
If totalBytesToDownload = 0 Then
totalBytesToDownload = TotalBytes
txtBytesToDownload.Text = totalBytesToDownload.ToString("N", nfi)
End If
If downloadedBytes >= totalBytesToDownload Then
dlCurrentspeed = 0
dlStopWatch.Stop()
testEndTickDownload = My.Computer.Clock.TickCount
testDeltaDownload = (testEndTickDownload - testStartTickDownload) / 1000
If DLtimedOut = True Then
DownloadCompleted(TestStatus.Cancelled.ToString(), "")
Else
DownloadCompleted(TestStatus.Completed.ToString(), "")
End If
If currentCycleDownload <= cycleNumericUpDown.Value Then
If protocolComboBox.Text = "HTTP" Then
StartHttpDownload()
Else
StartFtpDownload()
End If
End If
End If
End Sub
要从工作线程（无论是显式创建、排队到线程池的工作项还是来自异步 API 的回调）异步更新 UI，请使用Control.BeginInvoke.
这不会在等待 UI 线程处理操作时阻塞工作线程。
但请记住，UI 线程不能假定异步操作完成的特定顺序（以特定顺序开始的两个相同的下载不太可能按该顺序完成：太多的外部因素会影响下载速度）。
最后，大多数BeginABC方法都需要调用相应的EndABC，但（有帮助）Control.BeginInvoke不需要。