VB.NET中基于两个字符的随机字符串生成

我试图创建一个预定义的行数，每个行都有预定义的字符数。允许的字符仅为0和1，并且是随机生成的

我通过以下代码实现了这一点：

    Dim _allowedChars As String = "01"
    Dim randomNumber As New Random()
    Dim chars As List(Of Char) = New List(Of Char)
    Dim allowedCharCount As Integer = _allowedChars.Length
    For o As Integer = 0 To rows - 1
        For a As Integer = 0 To rowCharacters - 1
            chars.Add(_allowedChars.Chars(CInt(Fix((_allowedChars.Length) * randomNumber.NextDouble()))))
        Next a
        For a As Integer = 0 To chars.Count - 1
            'results for each row go here in a textbox line
        Next a
        chars = New List(Of Char)
        'row o finished, new line and go for next row
    Next o

这非常有效，下面显示了设置5行和5个字符（仅由随机生成的0或1组成）的示例输出：

11101
00000
11011
00000
01011

现在我想给它添加一个额外的转折点：指定每行1的最小百分比，即“即使随机分布，每行至少应有20%的1”。百分比基于每行中字符的长度（代码中的可变rowCharacters）

有谁能帮我解决这个问题吗

谢谢

Dim _allowedChars As String = "01"
Dim randomNumber As New Random()
Dim chars As List(Of Char) = New List(Of Char)
Dim allowedCharCount As Integer = _allowedChars.Length
'
For o As Integer = 0 To rows - 1
  Do
    For a As Integer = 0 To rowCharacters - 1
        chars.Add(_allowedChars.Chars(CInt(Fix((_allowedChars.Length) * randomNumber.NextDouble()))))
    Next a
    For a As Integer = 0 To chars.Count - 1
        'results for each row go here in a textbox line
    Next a
    chars = New List(Of Char)
    'row o finished, new line and go for next row
  Loop Until IsValidPercent(chars, 20)
Next o


Function IsValidPercent(chars As List(Of Char), ReqPercentage as integer) as boolean
'
Dim counter as integer = 0
Dim qtyones as integer = 0
  '
  IsValidPercent = False
  for counter = 0 to chars.count -1
    if chars(counter) = "1" Then qtyones = qtyones + 1
  next
  if qtyones >= ((chars.count/100)*ReqPercentage) Then IsValidPercent = True
  '
End Function