Vb.net StreamWriter中不必要的重复

我有这个密码

  Dim sw As StreamWriter
    For x As Integer = 0 To 20
        Dim validchars As String = "cfeabd0123456789"

        Dim sb As New StringBuilder()
        Dim rand As New Random()
        For i As Integer = 1 To 32
            Dim idx As Integer = rand.Next(0, validchars.Length)
            Dim randomChar As Char = validchars(idx)
            sb.Append(randomChar)
        Next i

        Dim randomString = sb.ToString()
        sw = File.AppendText("C:\file.txt")
        sw.WriteLine(randomString)
        sw.Close()
    Next

它所做的是创建20个随机句子，并在第3行声明“Validchars”，然后将输出写入带有附加功能的文本文件。我想每行写一个输出，例如：

4926022cabea67acc9c95035ff6ec492
7ca00313c590f990fa797c73ec1d3305
303a7364c220f3d02c5df8b5b39e00ae

但我遇到的问题是，它多次重复这些行，下面是一个示例输出（我删除了一些行以使其更短）：

---

正如您所看到的，它不是每行放置一个输出，而是重复多次输出，然后对下一个输出执行相同的操作。。。请帮助从循环中删除随机项

Sub GenerateRandomFileContent()
    Dim rand As New Random()
    Dim sw As StreamWriter
    For x As Integer = 0 To 20
        Dim validchars As String = "cfeabd0123456789"

        Dim sb As New StringBuilder()

        For i As Integer = 1 To 32
            Dim idx As Integer = rand.Next(0, validchars.Length)
            Dim randomChar As Char = validchars(idx)
            sb.Append(randomChar)
        Next i

        sb.Append(Environment.NewLine)  ' Remove this line if not needed

        ' Appends the Text to file
        Dim randomString = sb.ToString()
        sw = File.AppendText("C:\file.txt")
        sw.WriteLine(randomString)
        sw.Close()

        ' To Append this Text you could use just these lines below
        'Dim randomString = sb.ToString()
        'File.AppendAllText("C:\file.txt", randomString)
    Next
End Sub

---

New Random

在没有其他参数或设置的情况下，总是从同一位置重新启动。不完全是这样，New Random（）将使用依赖于时间的默认种子值初始化Random类的新实例。循环非常快，然后一些线得到相同的毫秒，和相同的sandom种子。正如您得到的答案中所解释的，重复与

StreamWriter

没有任何关系。无论如何，你应该“更恰当地”使用它。将其初始化为

sw as StreamWriter=New StreamWriter（“C:\file.txt”，True）

就足以追加文件（您不需要任何东西都使用

sw=file.AppendText（“C:\file.txt”）

位）。另外，您可能有兴趣使用语句将其放入

中（这将避免最后一个
sw.Close（）
，并将正确地处理它）。@Tony回答得好。但是OP使用的是
StreamWriter
，并认为这就是他得到不想要的行为的原因；在你的解决方案中，你已经取代了它；可能会被误解为“最好不要使用StreamWriter”（事实并非如此）。谢谢你，我不理解你所说的，并将StreamWriter放回原处。我还允许使用使用File.AppendAllText的其他代码进行注释
Sub GenerateRandomFileContent()
    Dim rand As New Random()
    Dim sw As StreamWriter
    For x As Integer = 0 To 20
        Dim validchars As String = "cfeabd0123456789"

        Dim sb As New StringBuilder()

        For i As Integer = 1 To 32
            Dim idx As Integer = rand.Next(0, validchars.Length)
            Dim randomChar As Char = validchars(idx)
            sb.Append(randomChar)
        Next i

        sb.Append(Environment.NewLine)  ' Remove this line if not needed

        ' Appends the Text to file
        Dim randomString = sb.ToString()
        sw = File.AppendText("C:\file.txt")
        sw.WriteLine(randomString)
        sw.Close()

        ' To Append this Text you could use just these lines below
        'Dim randomString = sb.ToString()
        'File.AppendAllText("C:\file.txt", randomString)
    Next
End Sub