VB.NET Randome Function to replace values - vb.net

Question

I have a Random Function in vb.net like this which returns the 6-digit alphanumeric string like this.
Public Function rand() As String
Dim rng As Random = New Random
Dim sb As New StringBuilder
' Selection of pure numbers sequence or mixed one
Dim pureNumbers = rng.Next(1, 11)
If pureNumbers < 7 Then
' Generate a sequence of only digits
Dim number As Integer = rng.Next(1, 1000000)
Dim digits As String = number.ToString("000000")
For i As Integer = 1 To 6
Dim idx As Integer = rng.Next(0, digits.Length)
sb.Append(digits.Substring(idx, 1))
Next
Else
' Generate a sequence of digits and letters
Dim s As String = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
For i As Integer = 1 To 6
Dim idx As Integer = rng.Next(0, 36)
sb.Append(s.Substring(idx, 1))
Next
End If
Return sb.ToString()
End Function
The problem is that when it returns 0 or O or 1 or I and so on {"1", "I", "O", "0", "5", "S", "7"}
I want to replce these character with 'A' and then should return the final random string.

Answer 1

If I understand you correctly, you want something like this (untested):
dim exceptionLetters = _
{"1", "I", "O", "0", "5", "S", "7"}
Dim s As String = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
For i As Integer = 1 To 6
Dim idx As Integer = rng.Next(0, 36)
Dim ltr = s.Substring(idx, 1)
if (exceptionLetters.Contains(ltr))
Return sb
End If
sb.Append(ltr);
Next