Imports System
Module Program
Function GenerateNDigitNumber(n As Integer) As Long
If n < 1 Then
Throw New ArgumentException("n must be a positive integer (>= 1).")
End If
Dim rnd As New Random()
Dim lowerBound As Long = If(n > 1, CLng(Math.Pow(10, n - 1)), 0)
Dim upperBound As Long = CLng(Math.Pow(10, n)) - 1
Dim range As Long = upperBound - lowerBound + 1
' Random.NextDouble gives [0.0, 1.0), scale to range
Dim r As Long = CLng(rnd.NextDouble() * range) + lowerBound
Return r
End Function
Sub Main()
Console.WriteLine(GenerateNDigitNumber(1))
Console.WriteLine(GenerateNDigitNumber(4))
Console.WriteLine(GenerateNDigitNumber(10))
End Sub
End Module
' run:
'
' 2
' 2507
' 1999131444
'
