如何将 BLOB 从 vb.net winforms 应用程序流式传输到 SQL 服务器并报告进度
How can I stream a BLOB from vb.net winforms application to SQL Server and report progress
我正在尝试将文件（可能很大）从我的 VB.Net Winforms 应用程序上传到 SQL Server 2008（C# 答案也可以接受）。
文件使用 SQL 服务器的 FILESTREAM 数据类型存储为 Varbinary(MAX)。
我通过传入一个 FileStream 作为 SqlParameter 将文件发送到服务器。
这没问题。但是，由于大文件需要一段时间才能上传，我想将进度报告回 UI 上的 ProgressBar。
我很确定我需要使用 Async/Await。主要问题实际上是获取进度值。因为我没有对 FileStream 做任何事情，只是将它作为 SqlParameter 传递，所以我不知道如何才能取回进度值。我怎样才能做到这一点？
我考虑过将流复制到另一个流并在那里获取进度值，但我认为这意味着将整个文件读入内存，我什至不确定它是否有效。
是否有 FileStream 的 Async 方法可以满足我的需要？还是有更好的方法让我做到这一点？
谢谢。
只是想让你知道我做了什么来解决这个问题...
我很清楚这个解决方案远非理想。一定有更好的方法，我仍在寻求改进它……但目前，它似乎可以满足我的需要。如有任何意见或建议，我们将不胜感激。
请在下面查看我简化的、完整注释的代码：
//Create the FileStream
Using SourceStream As New FileStream("PathToTheFile", FileMode.Open)
//Set the max value of your ProgressBar to the length of the stream
ProgressPb.Maximum = SourceStream.Length
//Start the task of sending the file to the DB (saving a reference to the task for later use.
Dim FileUpload As Task(Of Boolean) = Task.Run(Function() SendToDB())
//declare a variable to hold the last known position in the stream
Dim LastPosition As Long = 0
//loop until we we are done (until the current position is at the end of the stream)
Do
//only do something if the position in the strang has changed since we last checked.
If SourceStream.Position <> LastPosition Then
//save the current position for next time
LastPosition = SourceStream.Position
//set the value of your progress bar to the current position in the stream
ProgressPb.Value = SourceStream.Position
//set your status label text as you wish
StatusLbl.Text = "Uploading: " & Math.Round(SourceStream.Position / 1048576) & "MB of " & Math.Round(SourceStream.Length / 1048576) & "MB"
//call do events to save locking up your UI
Application.DoEvents()
End If
//limit the checks (8 times per second seems reasonably responsive)
Threading.Thread.Sleep(1000 / 8)
Loop Until LastPosition = SourceStream.Position
//set your status label text as "Finalising" or similar (there is a short delay of 1-2 seconds after we reach the end of the stream but before we recieve a response back from the DB).
StatusLbl.Text = "Uploading: " & Math.Round(SourceStream.Position / 1048576) & "MB of " & Math.Round(SourceStream.Length / 1048576) & "MB Complete. Finalising..."
//wait for the response from the database
Res = Await FileUpload
//set your status label text "Complete" or similar
StatusLbl.Text = "Uploading: " & Math.Round(SourceStream.Position / 1048576) & "MB of " & Math.Round(SourceStream.Length / 1048576) & "MB Complete. Finalising... Complete!"
//check the result from the database and do stuff accordingly.
If Res Then
MsgBox("Success")
Else
MsgBox("Failed")
End If
End Using
编辑
只是一个更新。我已将代码重构为 "StreamWatcher" class。请参阅下面 class 的代码：
Imports System.IO
Public Class StreamWatcher
Private Const MaxProgressEventsPerSecond As Integer = 200
Private Property _Stream As Stream
Private Property _PreviousPosision As Long
Public ReadOnly Property StreamPosition As Long
Get
If IsNothing(_Stream) Then
Return 0
Else
Return _Stream.Position
End If
End Get
End Property
Public ReadOnly Property StreamLength As Long
Get
If IsNothing(_Stream) Then
Return 0
Else
Return _Stream.Length
End If
End Get
End Property
Private Property _TimeStarted As DateTime? = Nothing
Private Property _TimeFinished As DateTime? = Nothing
Public ReadOnly Property SecondsTaken As Double
Get
If IsNothing(_TimeStarted) Then
Return 0.0
Else
If IsNothing(_TimeFinished) Then
Return (DateTime.Now - _TimeStarted.Value).TotalSeconds
Else
Return (_TimeFinished.Value - _TimeStarted.Value).TotalSeconds
End If
End If
End Get
End Property
Private Property _UpdatesCalled As Integer = 0
Public ReadOnly Property Updates As Integer
Get
Return _UpdatesCalled
End Get
End Property
Private Property _Progress As IProgress(Of EventType)
Private Enum EventType
Progressed
Completed
End Enum
Public Event Progressed()
Public Event Completed()
Public Sub Watch(ByRef StreamToWatch As Stream)
Reset()
_Stream = StreamToWatch
Dim ProgressHandler As New Progress(Of EventType)(Sub(Value) EventRaiser(Value))
_Progress = TryCast(ProgressHandler, IProgress(Of EventType))
_TimeStarted = DateTime.Now
Task.Run(Sub() MonitorStream())
End Sub
Private Sub MonitorStream()
Do
If _PreviousPosision <> StreamPosition Then
_PreviousPosision = StreamPosition
_Progress.Report(EventType.Progressed)
//limit events to max events per second
Task.Delay(1000 / MaxProgressEventsPerSecond).Wait()
End If
Loop Until (Not IsNothing(_Stream)) AndAlso (StreamPosition = StreamLength)
_TimeFinished = DateTime.Now
_Progress.Report(EventType.Completed)
End Sub
Private Sub EventRaiser(ByVal EventToRaise As EventType)
Select Case EventToRaise
Case EventType.Progressed
_UpdatesCalled += 1
RaiseEvent Progressed()
Case EventType.Completed
_UpdatesCalled += 1
RaiseEvent Completed()
End Select
End Sub
Private Sub Reset()
_Stream = Nothing
_PreviousPosision = 0
_TimeStarted = Nothing
_TimeFinished = Nothing
_UpdatesCalled = 0
End Sub
End Class
用法是这样的：
Private WithEvents StreamWatcher As New StreamWatcher
Private Async Sub SaveBtn_Click(sender As Object, e As EventArgs) Handles SaveBtn.Click
Dim Res As Boolean
Using FS As New FileStream("MyFilePath", FileMode.Open)
//this attaches the the watcher to the stream
StreamWatcher.Watch(FS)
ProgressBar.Maximum = FS.Length
//This waits for the function to finish before continuing, without locking up the UI... be careful not to dispose the stream before it's finished.
Res = Await Task.Run(Function() MySendToDBFunction(MyParam1))
StatusLbl.Text += " Complete!"
End Using
If Res Then
MessageBox.Show("Success")
Else
MessageBox.Show("Fail")
End If
End Sub
//Called whenever the position in the stream changes (upto the max calls per second as defined in the StreamWatcher class - 200 seems to be more than enough))
Private Sub FSWithProgeress_Progressed() Handles StreamWatcher.Progressed
ProgressBar.Value = StreamWatcher.StreamPosition
StatusLbl.Text = "Uploading: " & Math.Round(StreamWatcher.StreamPosition / 1048576) & "MB of " & Math.Round(StreamWatcher.StreamLength / 1048576) & "MB"
End Sub
//called once the end of the stream is reached
Private Sub FSWithProgeress_Completed() Handles StreamWatcher.Completed
StatusLbl.Text = "Upload: Complete. Finalising..."
End Sub
我正在尝试将文件（可能很大）从我的 VB.Net Winforms 应用程序上传到 SQL Server 2008（C# 答案也可以接受）。
文件使用 SQL 服务器的 FILESTREAM 数据类型存储为 Varbinary(MAX)。
我通过传入一个 FileStream 作为 SqlParameter 将文件发送到服务器。
这没问题。但是，由于大文件需要一段时间才能上传，我想将进度报告回 UI 上的 ProgressBar。
我很确定我需要使用 Async/Await。主要问题实际上是获取进度值。因为我没有对 FileStream 做任何事情，只是将它作为 SqlParameter 传递，所以我不知道如何才能取回进度值。我怎样才能做到这一点？
我考虑过将流复制到另一个流并在那里获取进度值，但我认为这意味着将整个文件读入内存，我什至不确定它是否有效。
是否有 FileStream 的 Async 方法可以满足我的需要？还是有更好的方法让我做到这一点？
谢谢。
只是想让你知道我做了什么来解决这个问题...
我很清楚这个解决方案远非理想。一定有更好的方法，我仍在寻求改进它……但目前，它似乎可以满足我的需要。如有任何意见或建议，我们将不胜感激。
请在下面查看我简化的、完整注释的代码：
//Create the FileStream
Using SourceStream As New FileStream("PathToTheFile", FileMode.Open)
//Set the max value of your ProgressBar to the length of the stream
ProgressPb.Maximum = SourceStream.Length
//Start the task of sending the file to the DB (saving a reference to the task for later use.
Dim FileUpload As Task(Of Boolean) = Task.Run(Function() SendToDB())
//declare a variable to hold the last known position in the stream
Dim LastPosition As Long = 0
//loop until we we are done (until the current position is at the end of the stream)
Do
//only do something if the position in the strang has changed since we last checked.
If SourceStream.Position <> LastPosition Then
//save the current position for next time
LastPosition = SourceStream.Position
//set the value of your progress bar to the current position in the stream
ProgressPb.Value = SourceStream.Position
//set your status label text as you wish
StatusLbl.Text = "Uploading: " & Math.Round(SourceStream.Position / 1048576) & "MB of " & Math.Round(SourceStream.Length / 1048576) & "MB"
//call do events to save locking up your UI
Application.DoEvents()
End If
//limit the checks (8 times per second seems reasonably responsive)
Threading.Thread.Sleep(1000 / 8)
Loop Until LastPosition = SourceStream.Position
//set your status label text as "Finalising" or similar (there is a short delay of 1-2 seconds after we reach the end of the stream but before we recieve a response back from the DB).
StatusLbl.Text = "Uploading: " & Math.Round(SourceStream.Position / 1048576) & "MB of " & Math.Round(SourceStream.Length / 1048576) & "MB Complete. Finalising..."
//wait for the response from the database
Res = Await FileUpload
//set your status label text "Complete" or similar
StatusLbl.Text = "Uploading: " & Math.Round(SourceStream.Position / 1048576) & "MB of " & Math.Round(SourceStream.Length / 1048576) & "MB Complete. Finalising... Complete!"
//check the result from the database and do stuff accordingly.
If Res Then
MsgBox("Success")
Else
MsgBox("Failed")
End If
End Using
编辑
只是一个更新。我已将代码重构为 "StreamWatcher" class。请参阅下面 class 的代码：
Imports System.IO
Public Class StreamWatcher
Private Const MaxProgressEventsPerSecond As Integer = 200
Private Property _Stream As Stream
Private Property _PreviousPosision As Long
Public ReadOnly Property StreamPosition As Long
Get
If IsNothing(_Stream) Then
Return 0
Else
Return _Stream.Position
End If
End Get
End Property
Public ReadOnly Property StreamLength As Long
Get
If IsNothing(_Stream) Then
Return 0
Else
Return _Stream.Length
End If
End Get
End Property
Private Property _TimeStarted As DateTime? = Nothing
Private Property _TimeFinished As DateTime? = Nothing
Public ReadOnly Property SecondsTaken As Double
Get
If IsNothing(_TimeStarted) Then
Return 0.0
Else
If IsNothing(_TimeFinished) Then
Return (DateTime.Now - _TimeStarted.Value).TotalSeconds
Else
Return (_TimeFinished.Value - _TimeStarted.Value).TotalSeconds
End If
End If
End Get
End Property
Private Property _UpdatesCalled As Integer = 0
Public ReadOnly Property Updates As Integer
Get
Return _UpdatesCalled
End Get
End Property
Private Property _Progress As IProgress(Of EventType)
Private Enum EventType
Progressed
Completed
End Enum
Public Event Progressed()
Public Event Completed()
Public Sub Watch(ByRef StreamToWatch As Stream)
Reset()
_Stream = StreamToWatch
Dim ProgressHandler As New Progress(Of EventType)(Sub(Value) EventRaiser(Value))
_Progress = TryCast(ProgressHandler, IProgress(Of EventType))
_TimeStarted = DateTime.Now
Task.Run(Sub() MonitorStream())
End Sub
Private Sub MonitorStream()
Do
If _PreviousPosision <> StreamPosition Then
_PreviousPosision = StreamPosition
_Progress.Report(EventType.Progressed)
//limit events to max events per second
Task.Delay(1000 / MaxProgressEventsPerSecond).Wait()
End If
Loop Until (Not IsNothing(_Stream)) AndAlso (StreamPosition = StreamLength)
_TimeFinished = DateTime.Now
_Progress.Report(EventType.Completed)
End Sub
Private Sub EventRaiser(ByVal EventToRaise As EventType)
Select Case EventToRaise
Case EventType.Progressed
_UpdatesCalled += 1
RaiseEvent Progressed()
Case EventType.Completed
_UpdatesCalled += 1
RaiseEvent Completed()
End Select
End Sub
Private Sub Reset()
_Stream = Nothing
_PreviousPosision = 0
_TimeStarted = Nothing
_TimeFinished = Nothing
_UpdatesCalled = 0
End Sub
End Class
用法是这样的：
Private WithEvents StreamWatcher As New StreamWatcher
Private Async Sub SaveBtn_Click(sender As Object, e As EventArgs) Handles SaveBtn.Click
Dim Res As Boolean
Using FS As New FileStream("MyFilePath", FileMode.Open)
//this attaches the the watcher to the stream
StreamWatcher.Watch(FS)
ProgressBar.Maximum = FS.Length
//This waits for the function to finish before continuing, without locking up the UI... be careful not to dispose the stream before it's finished.
Res = Await Task.Run(Function() MySendToDBFunction(MyParam1))
StatusLbl.Text += " Complete!"
End Using
If Res Then
MessageBox.Show("Success")
Else
MessageBox.Show("Fail")
End If
End Sub
//Called whenever the position in the stream changes (upto the max calls per second as defined in the StreamWatcher class - 200 seems to be more than enough))
Private Sub FSWithProgeress_Progressed() Handles StreamWatcher.Progressed
ProgressBar.Value = StreamWatcher.StreamPosition
StatusLbl.Text = "Uploading: " & Math.Round(StreamWatcher.StreamPosition / 1048576) & "MB of " & Math.Round(StreamWatcher.StreamLength / 1048576) & "MB"
End Sub
//called once the end of the stream is reached
Private Sub FSWithProgeress_Completed() Handles StreamWatcher.Completed
StatusLbl.Text = "Upload: Complete. Finalising..."
End Sub