Question Random numbers

[Bozz]

I've got ten textboxes that I want to fill with random numbers when the user clicks "Fill" on a menu. So I put the boxes into a ArrayList called TextBoxes and wrote the next two procedures:

Private Function ProduceRandomNumber(ByVal Min As Integer, ByVal Max As Integer) As Integer
Dim Num As New Random()
Return Num.Next(Min, Max)
End Function

Private Sub FillToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles FillToolStripMenuItem.Click
Dim RandomEntry As Integer
For Each TBox As TextBox In Textboxes
RandomEntry = ProduceRandomNumber(0, 9999)
TBox.Text = CStr(RandomEntry)
Next
End Sub

This fills all the boxes fine, but the first few are all identical, the next few are a different value but all the same, sometimes there's a couple more identical. It varies.
Q. What the heck is going on around here?

 

[JohnH]

Use only a single instance of the Random class to produce all random values.

Private rand As New Random()

 

[Bozz]

Thanks JohnH, much better.

Private Sub FillToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles FillToolStripMenuItem.Click
Dim rand As New Random()
For Each TBox As TextBox In Textboxes
TBox.Text = CStr(rand.Next(9999))
Next
End Sub

Now why didn't I think of that? (Rhetorical question)

 

[JohnH]

Now you create a new Random instance each time menu item is clicked, it would be better if you did what I suggested and only used a single instance of the Random class.

Now why didn't I think of that?

Probably because you didn't read the documentation for Random class.