Generate a random string

[SIMIN]

Hi,

I wanna generate a random alphanumeric in the following format:

 

d4g2o5m3-u1q2-s7z9-z6o8-o3q2c2m5m2s9

 

So with your help, I wrote a public function like this:

Public Function GenerateContactID() As String
   Dim MyRandom As New Random
   GenerateContactID = Nothing
   For MyLoop As Integer = 1 To 8
       If MyLoop Mod 2 = 1 Then
           GenerateContactID = GenerateContactID + Convert.ToChar(MyRandom.Next(97, 123))
       End If
       If MyLoop Mod 2 = 0 Then
           GenerateContactID = GenerateContactID + MyRandom.Next(1, 10).ToString
       End If
   Next
   GenerateContactID = GenerateContactID + "-"
   For MyLoop As Integer = 1 To 4
       If MyLoop Mod 2 = 1 Then
           GenerateContactID = GenerateContactID + Convert.ToChar(MyRandom.Next(97, 123))
       End If
       If MyLoop Mod 2 = 0 Then
           GenerateContactID = GenerateContactID + MyRandom.Next(1, 10).ToString
       End If
   Next
   GenerateContactID = GenerateContactID + "-"
   For MyLoop As Integer = 1 To 4
       If MyLoop Mod 2 = 1 Then
           GenerateContactID = GenerateContactID + Convert.ToChar(MyRandom.Next(97, 123))
       End If
       If MyLoop Mod 2 = 0 Then
           GenerateContactID = GenerateContactID + MyRandom.Next(1, 10).ToString
       End If
   Next
   GenerateContactID = GenerateContactID + "-"
   For MyLoop As Integer = 1 To 4
       If MyLoop Mod 2 = 1 Then
           GenerateContactID = GenerateContactID + Convert.ToChar(MyRandom.Next(97, 123))
       End If
       If MyLoop Mod 2 = 0 Then
           GenerateContactID = GenerateContactID + MyRandom.Next(1, 10).ToString
       End If
   Next
   GenerateContactID = GenerateContactID + "-"
   For MyLoop As Integer = 1 To 12
       If MyLoop Mod 2 = 1 Then
           GenerateContactID = GenerateContactID + Convert.ToChar(MyRandom.Next(97, 123))
       End If
       If MyLoop Mod 2 = 0 Then
           GenerateContactID = GenerateContactID + MyRandom.Next(1, 10).ToString
       End If
   Next
End Function

However, sometimes the call to this function will return the same result, I mean it's not completely random?

How that's possible?

Thank you :)

Edited January 18, 2009 by SIMIN

[PlausiblyDamp]

Not properly tested but I would have written it as

   Dim r As New Random

   Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

       Dim GenerateContactID As String = String.Empty

       For MyLoop As Integer = 1 To 8
           If MyLoop Mod 2 = 1 Then
               GenerateContactID &= Convert.ToChar(r.Next(97, 122))
           Else
               GenerateContactID &= r.Next(0, 9).ToString()
           End If
       Next
       Debug.WriteLine(GenerateContactID)
   End Sub

 

Although things like CInt etc. are perfectly valid in .Net I tend to avoid them simply because I use both C# and VB.Net and remembering two ways to do things is twice the effort of remembering one way ;)