Visual Basic中的安全复制文件

Question

以下代码是从C＃代码中删除的。我想知道代码中For .... To ...语句的重要性是什么？

Public Sub CopyFile(sourceFile  As String, backupFile  As String, overwrite As Boolean)
If String.IsNullOrEmpty(sourceFile) Then
    Throw New ArgumentNullException("sourceFile")
End If
If String.IsNullOrEmpty(backupFile) Then
    Throw New ArgumentNullException("backupFile")
End If
' According to MSDN Certain file attributes, Hidden and ReadOnly, can be combined. Other attributes, such as Normal, must be used alone. 
If File.Exists(backupFile) Then
    File.SetAttributes(backupFile, FileAttributes.Normal)
End If
            ' ????????
For index As Integer = 0 To 9
    Try
        File.Copy(sourceFile, backupFile, overwrite)
        Exit Try
    Catch ex  As FileNotFoundException
        Throw
    Catch ex As Exception
        If Not overwrite Then
            Throw
        End If
        If index = 9 Then
            Throw
        End If
        Thread.Sleep(1000)
    End Try
Next
End Sub