我的代码基本上将3个随机变量输入到文本文件中，使用“:”分隔每个变量。我的代码的第二部分基本上再次读取文本文件，并使用我之前输入的 MID 函数来切割字符串，以获取第二个变量，然后将其添加到一个数组中。然而，当我输出数组时，它都是0。我尝试找出问题所在，但我不知道。
以下是我的代码：
Dim r1, r2, r3, counter, counter1, counter2, sep As Integer
Dim line As String
Dim middleline(20)
line = ""
counter1 = 0
sep = 0
FileSystem.FileOpen(1, "C:\Users\user\OneDrive\Desktop\binarysearch.txt", OpenMode.Output, OpenAccess.Write)
For counter = 1 To 20
    If Rnd() = 0.21 Then
        r1 = -1
    Else
        Do
            r1 = Rnd() * 100
        Loop Until r1 <= 20
    End If
    Do
        r2 = Rnd() * 100
    Loop Until r2 >= 10 AndAlso r2 <= 50
    If Rnd() = 0.21 Then
        r3 = -1
    Else
        Do
            r3 = Rnd() * 100
        Loop Until r3 <= 20
    End If
    line = r1 & ":" & r2 & ":" & r3
    FileSystem.WriteLine(1, line)
Next
Console.WriteLine("生成成功。")
For counter = 1 To 20
    middleline(counter) = 0
Next
For counter = 1 To 20
    FileSystem.PrintLine(1, line)
    For counter1 = 1 To Len(line)
        If Mid(line, 1, counter1) = ":" Then
            sep += 1
        End If
        If sep = 1 Then
            middleline(counter2) = middleline(counter2) & Mid(line, 1, counter1)
            counter2 += counter2
        End If
    Next
Next
For counter = 1 To 20
    Console.WriteLine(middleline(counter))
Next
Console.WriteLine(middleline)

I'm not 100% sure where your code goes wrong, but I have given it a little rewrite and this appears to be working ok.
<br>I changed the random number generation as I felt your loop was a little heavy duty.
<br>Also switched the file handling to newer methods.
Private Shared RndGenMachine As Random = New Random
Public Sub DoWork(FileName As String)
    Dim r1, r2, r3 As Integer
    Dim middleline As List(Of String) = New List(Of String)
    'build the initial file
    Using sw As New StreamWriter(FileName, True)
        For counter As Integer = 1 To 20
            r1 = RndGenMachine.Next(0, 20)
            r3 = RndGenMachine.Next(0, 20)
            r2 = RndGenMachine.Next(10, 50)
            Dim line As String = $"{r1}:{r2}:{r3}"
            sw.WriteLine(line)
        Next
    End Using
    Console.WriteLine("Generated successfully.")
    'read it back for parsing
    Dim lines As IEnumerable(Of String) = File.ReadLines(FileName)
    For lineCounter = 0 To lines.Count - 1
        Dim splits() As String = lines(lineCounter).Split(Convert.ToChar(":"))
        middleline.Add(splits(1))
    Next
    For Each middlelinevalue As String In middleline
        Console.WriteLine(middlelinevalue)
    Next
End Sub

Public Sub DoWorkOldStyle(FileName As String, iterations As Integer)
    Console.WriteLine("Starting generation...")
    Dim r1, r2, r3 As Integer
    'build the initial file
    FileSystem.FileOpen(1, FileName, OpenMode.Output, OpenAccess.Write)
    For counter As Integer = 1 To iterations
        r1 = RndGenMachine.Next(0, 20)
        r3 = RndGenMachine.Next(0, 20)
        r2 = RndGenMachine.Next(10, 50)
        Dim line As String = $"{r1}:{r2}:{r3}"
        FileSystem.WriteLine(1, line)
    Next
    FileSystem.FileClose(1)
    Console.WriteLine("Generated successfully. Starting evaluation...")
    'read it back for parsing
    FileSystem.FileOpen(1, FileName, OpenMode.Input, OpenAccess.Read)
    Dim middleline As List(Of String) = New List(Of String)
    While Not EOF(1)
        Dim line As String = LineInput(1)
        Dim splits() As String = line.Split(Convert.ToChar(":"))
        middleline.Add(splits(1))
    End While
    FileClose(1)
    For Each middlelinevalue As String In middleline
        Console.WriteLine(middlelinevalue)
    Next
    Console.WriteLine("Evalutaion complete.")
End Sub