[RESOLVED] [2008] How to pick a random number between X and Y Need help with my Code.

[hazedoutdesi]

I have this code to pick a random number Between X and Y
X = Minimum Number
Y = Maximum Number

But the problem is i wanted to know if there is a better random function than the one i have.

Because right now i put

Min = 1
Max= 2

and it keeps picking 1

if i had min =1 and max =2 i want it to pick 1 sometimes and 2 sometimes

and now i tried min = 1 max = 3
and it never picks 3, it only picks 1 and 2

Code:

Public Class Form1
    Public Function RandomNumber(ByVal MinNumber As Integer, ByVal MaxNumber As Integer) As Integer
        Dim r As New Random(System.DateTime.Now.Millisecond)
        Return Convert.ToInt32(r.Next(MinNumber, MaxNumber))
    End Function
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
 
    End Sub
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        MsgBox(RandomNumber(1, 3))
    End Sub
End Class

[Shaggy Hiker]

The Random object returns a number that includes the lower bound, but does NOT include the upper bound. Therefore, if you want to include both min and max, you need to pick a random number from Min to Max+1

[Lord Orwell]

You need to add +1 to your max number. If you didn't round your answer off you would see why.

[hazedoutdesi]

Thanks a lot guys +1 worked great.

[babyjesus]

i noticed if you use your code in a replace string it will bring up the same chr's... heres how to get a more random number

Public Function RandomNumber(ByVal Lowest As Double, ByVal Highest As Double) As Double
        Dim i As Double
 
        Do : Application.DoEvents()
            Randomize()
            i = CDbl((Rnd() * Highest) + Lowest)
        Loop Until i <= Highest
        Return i
    End Function

[jmcilhinney]

i noticed if you use your code in a replace string it will bring up the same chr's... heres how to get a more random number

Public Function RandomNumber(ByVal Lowest As Double, ByVal Highest As Double) As Double
        Dim i As Double
 
        Do : Application.DoEvents()
            Randomize()
            i = CDbl((Rnd() * Highest) + Lowest)
        Loop Until i <= Highest
        Return i
    End Function

The problem with the original code is the fact that a new Random object is created each time a random number is required. As such, if you request multiple random numbers in quick succession the same number will be generated each time because the same implicit seed is used. The solution is definitely not to revert that old VB6-style code. The answer is to just create a single Random object and then to call its Next method multiple times. the RandomNumber method is pointless because you should simply be calling Next. Also, the Convert.ToInt32 is pointless because Next already returns an Int32. The code only needs to be:

Public Class Form1

    Private rng As New Random

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        MsgBox(Me.rng.Next(1, 3 + 1).ToString())
    End Sub
End Class

[Shaggy Hiker]

Aside from that, putting the Randomize call into the inner loop will cause the same trouble that creating the Random object in the sub is causing. Every time that Randomize is called, it will re-seed the VB6-style random number generator with the current system time. The DoEvents slows things down, but not enough for the system time to change between calls to Randomize, so you will just get the same number over and over again until the time increments. Technically, you could use that loop to time the loop itself, but that's kind of silly.

[Half]

I think it's time Shaggy Hiker tests how long it takes to brute force the generated 'random' if we know the week it was generated

[Shaggy Hiker]

I don't even understand the question??? But I think I agree with it.