Question

我是Visual Basic的新手，也是一般新编码的新手。目前我正在使用一个使用filewatcher的程序。但如果我试试这个：

Public Class Form1

Private WithEvents fsw As IO.FileSystemWatcher

Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    fsw = New IO.FileSystemWatcher("PATH")
    fsw.EnableRaisingEvents = True
    '  fsw.Filter = "*.settings"

End Sub


Private Sub GetSettingsFromFile()    
Some Code
More Code
CheckBox1.Checked = True   
End Sub

Private Sub fsw_Changed(sender As Object, e As FileSystemEventArgs) Handles fsw.Changed
    fsw.EnableRaisingEvents = False 'this is set because the file is changed many times in rapid succesion so I need to stop the Filewatcher from going of 200x (anyone has a better idea to do this?)
    Threading.Thread.Sleep(100)
    GetSettingsFromFile()
    fsw.EnableRaisingEvents = True 'enabling it again
End Sub
End Class

但是当我这样做（尝试更改表单中的任何内容）时，我收到此错误： System.InvalidOperationException（WinForms.IllegalCrossThreadCall）它不会阻止程序工作，但我想了解这里有什么问题以及为什么调试器会向我抛出这个问候

Answer 1

该事件正在辅助线程上引发。必须在UI线程上对UI进行任何更改。您需要封送对UI线程的方法调用并在那里更新UI。关于如何做到这一点的大量信息。这是一个例子：

Private Sub UpdateCheckBox1(checked As Boolean)
    If CheckBox1.InvokeRequired Then
        'We are on a secondary thread so marshal a method call to the UI thread.
        CheckBox1.Invoke(New Action(Of Boolean)(AddressOf UpdateCheckBox1), checked)
    Else
        'We are on the UI thread so update the control.
        CheckBox1.Checked = checked
    End If
End Sub

现在，无论您身在何处，无论您使用什么线程，都可以直接调用该方法。如果您已经在UI线程上，则控件将被更新。如果你在辅助线程上，那么该方法将第二次调用自己，这次是在UI线程上，控件将在第二次调用时更新。

使用filewatcher的WinForms.IllegalCrossThreadCall

1 个答案: