vb.net 编写固定宽度的文本文件

Writing a fixed-width text file

提问by Caben

I'm writing an app that creates a fixed-width text file. What I've already written works just fine, but I'm wondering if there is a more efficient method. (By efficient, I mean executes faster, not uses less code.)

我正在编写一个创建固定宽度文本文件的应用程序。我已经写的工作得很好，但我想知道是否有更有效的方法。（高效，我的意思是执行速度更快，而不是使用更少的代码。）

Here is the function I've created that pads or trims strings to the required length:

这是我创建的将字符串填充或修剪到所需长度的函数：

Private Function ToLen(ByRef strLen As String, ByRef intLen As Integer) As String

    Dim L As Integer = Len(strLen)
    If L < intLen Then
        Return strLen & Strings.Space(intLen - L)
    ElseIf L = intLen Then
        Return strLen
    Else
        Return Strings.Left(strLen, intLen)
    End If

End Function

Here is a simplified version of the code that calls it:

这是调用它的代码的简化版本：

Using MyFile1 As New StreamWriter("C:\Temp\MyFile.txt")
    Do
        ' loop through records
        MyFile1.WriteLine(ToLen(Item1, 10) & ToLen(Item2, 50) & ToLen(Item3, 25))
    Loop
End Using

回答by Steven Doggart

I would recommend using the new .NET methods for string manipulation rather than the old-style VB6 functions, for instance:

我建议使用新的 .NET 方法进行字符串操作，而不是旧式的 VB6 函数，例如：

Private Function ToLen(text As String, length As Integer)
    If text.Length > length Then
        Return text.SubString(0, length)
    Else
        Return text.PadRight(length)
    End If
End Function

Then, when you are writing to the file, don't concatenate the strings together. It would be more efficient to call Writemultiple times:

然后，当您写入文件时，不要将字符串连接在一起。Write多次调用会更有效：

Using MyFile1 As New StreamWriter("C:\Temp\MyFile.txt")
    Do
        ' loop through records
        MyFile1.Write(ToLen(Item1, 10))
        MyFile1.Write(ToLen(Item2, 50))
        MyFile1.WriteLine(ToLen(Item3, 25))
    Loop
End Using