在执行下一行代码之前,一行代码是否完成？

Question

只要该文件尚不存在,以下代码就会移动文件.如果是,则不会移动文件.

我的问题是关于File.Move.msgbox何时显示？文件完全移动后会显示,还是在File.Move执行完毕后显示.

根据文件大小,移动文件可能需要一段时间,因此我不希望msgbox显示,直到文件完全移动.

有没有更好的方法呢？

        For Each foundFile As String In My.Computer.FileSystem.GetFiles("C:\Temp\", FileIO.SearchOption.SearchAllSubDirectories, "*.zip")
            Dim foundFileInfo As New System.IO.FileInfo(foundFile)

            If My.Computer.FileSystem.FileExists("C:\Transfer\" & foundFileInfo.Name) Then
                Msgbox("File already exists and will not moved!")
                Exit Sub
            Else
                File.Move(foundFile, "C:\Transfer\" & foundFileInfo.Name)
                Msgbox("File has been moved!")
            End If
        Next

Answer 1

根据此来源,File.Move调用是同步的,这意味着只有在文件移动后才会显示您的msgbox,无论其大小如何.

为了完整起见,如果您不想阻止UI,可以尝试以下方法:

' This must be placed outside your sub/function
Delegate Sub MoveDelegate(iSrc As String, iDest As String)

' This line and the following go inside your sub/function
Dim f As MoveDelegate = AddressOf File.Move

' Call File.Move asynchronously
f.BeginInvoke(
    foundFile, 
    "C:\Transfer\" & foundFile, 
    New AsyncCallback(Sub(r As IAsyncResult)
                          ' this code is executed when the move is complete
                          MsgBox("File has been moved!")
                      End Sub), Nothing)

或者您可以探索新的异步/等待指令.