如何从 async await sub 更新 label.text？

Question

我正在使用文件流读取二进制文件，并且正在使用异步等待以避免冻结 UI

Await Task.Run(Sub()
 For i = 0 To file_len Step 512
   fs.Seek(i, SeekOrigin.Begin)       ' look into the next 4096 of the file
   fs.Read(array_for_fat, 0, 512)             ' read it to the buffer
   label2.text = i                      'getting the error here
  Next
 End Sub)

问题是我无法更新（我想更新有关应用程序已读取多少的信息）

label2.text = i

来自这个话题

请提供任何解决方案，如何从 async-await sub 更新文本框，或者我可以使用更适合我目的的东西？完整代码示例：

Private Async Sub Button15_Click(sender As Object, e As EventArgs) Handles Button15.Click

        OpenFileDialog1.FileName = ".bin file"
        If OpenFileDialog1.ShowDialog() = Windows.Forms.DialogResult.OK Then
            Label9.Text = System.IO.Path.GetFullPath(OpenFileDialog1.FileName)
        Else
            Exit Sub
        End If

        file_len = New System.IO.FileInfo(Label9.Text).Length.ToString
       If Label9.Text.Contains(".bin") Or Label9.Text.Contains(".BIN") Then
        Else
            Label9.Text = ""
       End If
        Using fs As New FileStream(Label9.Text, FileMode.Open, FileAccess.Read, FileShare.None)
      
            Await Task.Run(Sub()
               For i = 0 To file_len Step 512
                 fs.Seek(i, SeekOrigin.Begin)       ' look into the next 4096 of the file
                 fs.Read(array_for_fat, 0, 512)             ' read it to the buffer
                
              For Each position In Form1.Locate(array_for_fat, bytesToFind)
                    If array_for_fat(0) <> 1 Or array_for_fat(52) <> &H41 Then Continue For                
    'searching for proper data in the 512byte dump from file
                      i = file_len   'stop reading the file when found the dump we need
                       For b = 28 To 100 Step 2
                      If array_for_fat(b) = 0 Then                                                                                                         ' found? execute
                       Exit For
                      End If
                      result &= array_for_fat(b).ToString("X") & array_for_fat(b + 1).ToString("X")
                       Next
                      Exit For
                       Next
                Next
             End Sub)
 end using
end sub

和定位子代码（在字节数组中搜索字节模式）：

Public Function Locate(ByVal self As Byte(), ByVal candidate As Byte()) As Integer()
  If IsEmptyLocate(self, candidate) Then Return Empty
  Dim list = New List(Of Integer)()

 For i As Integer = 0 To self.Length - 1
    If Not IsMatch(self, i, candidate) Then Continue For
    list.Add(i)
 Next

 Return If(list.Count = 0, Empty, list.ToArray())
End Function

Public Function IsEmptyLocate(ByVal array As Byte(), ByVal candidate As 
  Byte()) 
     As Boolean
    Return array Is Nothing OrElse candidate Is Nothing OrElse array.Length = 
     0 OrElse candidate.Length = 0 OrElse candidate.Length > array.Length
 End Function

Public Function IsMatch(ByVal array As Byte(), ByVal position As Integer, 
 ByVal candidate As Byte()) As Boolean
If candidate.Length > (array.Length - position) Then Return False

For i As Integer = 0 To candidate.Length - 1
    If array(position + i) <> candidate(i) Then Return False
Next

Return True

结束函数

Answer 1

查看 How to: Make thread-safe calls to Windows Forms controls 了解更多详情。

将 label2.text = i 替换为此调用（来自文章）：

Private Sub WriteTextSafe(ByVal value As String)
    If label2.InvokeRequired Then
        Dim d = New SafeCallDelegate(AddressOf WriteTextSafe)
        label2.Invoke(d, New Object() {value})
    Else
        label2.Text = value
    End If
End Sub

另一个例子：

''' <summary>
''' Thead-safe add value to list.
''' </summary>
''' <param name="value">The value.</param>
Private Sub UpdateLabel2(value As String)
    If label2.InvokeRequired Then
        label2.Invoke(Sub() label2.Text = value)
    Else
       label2.Text = value
    End If
End Sub

提示：通过 naming 您的控件和变量，然后是 label1、label2，使您的 coding-life 减少 error-prone。一年多以后，当你 return 看到这段代码时，你会记得 label1 是什么而不用看表格吗？

Answer 2

你可以使用 Progress(Of T)：

Dim progress As IProgress(Of Integer) = New Progress(Of Integer)(Sub (value as Integer) label2.Text = value)
Await Task.Run(Sub()
 For i = 0 To file_len Step 512
   fs.Seek(i, SeekOrigin.Begin)
   fs.Read(array_for_fat, 0, 512)
   progress(i)
  Next
 End Sub)

如何从 async await sub 更新 label.text？

How to update label.text from async await sub?

vb.net

label

async-await