[RESOLVED] Random Number Problem

[mouse88]

Here is my function for generating a random number:

Public Function GenRandomNo(ByVal MinValue As Integer, ByVal MaxValue As Integer) As Integer

        Dim RndInst As New Random 'Create New Random'

        GenRandomNo = RndInst.Next(MinValue, MaxValue) 'Generate Random Integer Between The Min And Max Value'

    End Function

And here is where I am using it:

Public Function CheckPowerUp() As Boolean

        Dim RndNo As Integer = GenRandomNo(1, 5) 'Generate A Number Between 1 and 5'

        Select Case RndNo 'Check Generated Number, Return True If Number Is 5'
            Case 1
                Return False
            Case 2
                Return False
            Case 3
                Return False
            Case 4
                Return False
            Case 5
                Return True
        End Select

    End Function

I have put a breakpoint and created a test log and for some reason it is never generating a 5 only 1 to 4. Any ideas why this could be happening?

[stanav]

Have you read the documentation of the Random class, espcially the Next method?
I guess not.... To generate a random number between 1 and 5 inclusive, you need to do random.Next(1, 6)

[motil]

this:

GenRandomNo(1, 5) 'Generate A Number Between 1 and 5'

means: Generate number that equal to 1 and less then 5, change the 5 to 6 and you ready to go

[Shaggy Hiker]

The random object generates from MinValue to MaxValue - 1. Therefore, (1,5) will generate 1-4, not 1-5.

By the way, since you are creating the Random object in the sub, if you call that sub in a loop, your numbers will not be random at all. In fact, they will be a series of the same number if the loop is fast enough. The reason is that the random number generator is seeded on the current time. If the call to the sub is made fast enough, the time will be the same for subsequent calls. Random objects created with the same seed will return the same value.

To solve this, declare a single Random object at class or form scope and use that repeatedly, rather than creating one within a sub.

[Shaggy Hiker]

I didn't expect to be the first to answer that, but I didn't expect TWO people to get in ahead of me. However, I added a little extra value to my answer.

[mouse88]

Ok thanks for the help I think Ill declare the random once aswell as Im using XNA and the loop is at least 20fps so this will prob end up causing me some problems.

Thanks again

[Shaggy Hiker]

Yes, it certainly would cause issues. Your random would not be.