使用 in VB.net 的条件定义

Question

我想避免重复代码以有条件地写入日志文件，正如我在下面所做的那样。 VB.net有没有更好的解决办法？

If Not System.IO.File.Exists(log_file_address) Then
    Using log_file_stream as New System.IO.StreamWriter(log_file_address)
        log_file_stream.Writeline (current_time_string)
        log_file_stream.Writeline (" ")
        log_file_stream.Writeline (log_message)
        log_file_stream.Close()
    End Using
Else
    Using log_file_stream As IO.StreamWriter = System.IO.File.AppendText(log_file_address)
        log_file_stream.Writeline (current_time_string)
        log_file_stream.Writeline (" ")
        log_file_stream.Writeline (log_message)
        log_file_stream.Close()
    End Using
End If

可能是这样的：

Using log_file_stream as If(System.IO.File.Exists(log_file_address), _
                            System.IO.File.AppendText(log_file_address), _
                            New System.IO.StreamWriter(log_file_address))
    log_file_stream.Writeline (current_time_string)
    log_file_stream.Writeline (" ")
    log_file_stream.Writeline (log_message)
    log_file_stream.Close()
End Using

Answer 1

StreamWriter 的构造函数有一个 overload，其参数采用文件路径字符串和布尔开关来指示是否应该过度追加。请注意，如果文件不存在，则此参数无效，构造函数会创建一个新文件。

因此更改并让构造函数负责检查文件是否存在。

Using log_file_stream as New System.IO.StreamWriter(log_file_address, True)
    'Write to log file...
End Using

使用 in VB.net 的条件定义

Conditional Definition with Using in VB.net

vb.net

initialization

ternary-operator