random number selection and display

[Modibbo]

Hi there,

I'd like to submit this program I'm working on to thr forum.
I want to display 6 randomly generated numbers on 6 command buttons as captions at the click of another button. One number will be selected only once.
Here's my code:

Public Class Form1
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim x As Integer() = New Integer() {x(0), x(1), x(2), x(3), x(4), x(5)}
        Dim m_blnUsed As Boolean() = _
        New Boolean(x.GetUpperBound(0)) {}

        Dim objrandom As Random = New Random()
        Dim intrandom As Integer
        Do
            intrandom = objrandom.Next(0, m_blnUsed.Length)
        Loop Until m_blnUsed(intrandom) = False
        m_blnUsed(intrandom) = True

        Dim index As Integer
        For index = 0 To 5
            x(index) = x(intrandom)
        Next

        Button3.Text = Str(x(0))
        Button4.Text = Str(x(1))
        Button5.Text = Str(x(2))
        Button6.Text = Str(x(3))
        Button7.Text = Str(x(4))
        Button8.Text = Str(x(5))

    End Sub
    
End Class

I'm getting an error message

variable 'x' is used before it has been assigned a value. A null reference exception could result at runtime.

at the beginning where I'm declaring and initializing the array of integers x(0)

Can anyone help please.
Thanks

[Modibbo]

forgot to mention I'm using VB2005

[SammyB]

Dim x As Integer() = New Integer() {x(0), x(1), x(2), x(3), x(4), x(5)}

Think what you are telling VB to do:
"I want to declare an array of integers called x, and initialize it to the values in X(0), X(1), ..."
So, VB is saying, duh, you don't have anything in x, so I cannot use it to initialize anything, much less itself.

What do you really want to initialize x to?

[Killer42]

Also, I think there's a loop missing there. Unless I'm misreading the code, intrandom is only set once, so all six occurences of x (and hence the buttons) will be set to the same number.

[SammyB]

Also, I think there's a loop missing there. Unless I'm misreading the code, intrandom is only set once, so all six occurences of x (and hence the buttons) will be set to the same number.

Oh, no! This is the same thread as http://www.thescripts.com/forum/thread636691.html with the same mistakes!

OK. I will write an article on random number generation and post it in our new Articles Tab. I'll post a link here afterwards.

[Killer42]

Beat you to it, Sammy. :D

Here is the link.

[Modibbo]

thanks a lot sammyB, killer42 for all your help; i've been going trough all the material you've suggested, even some of it i read before by searching, but still can't get my head round it. nevertheless still trying, here's the modified code

Public Class Form1


    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim x As Integer() = New Integer(6) {}

        Dim randomgeberator As New Random
        Dim index As Integer
        For index = 0 To 5
            x(index) = randomgeberator.Next(0, 20)
        Next

        Button3.Text = Str(x(0))


        Button4.Text = Str(x(1))
        Button5.Text = Str(x(2))
        Button6.Text = Str(x(3))
        Button7.Text = Str(x(4))
        Button8.Text = Str(x(5))

    End Sub

End Class

i'm having this at runtime on the immediate window

A first chance exception of type 'System.IndexOu tOfRangeExcepti on' occurred in 2nd ind asgmt.exe
A first chance exception of type 'System.IndexOu tOfRangeExcepti on' occurred in 2nd ind asgmt.exe
A first chance exception of type 'System.IndexOu tOfRangeExcepti on' occurred in 2nd ind asgmt.exe
A first chance exception of type 'System.IndexOu tOfRangeExcepti on' occurred in 2nd ind asgmt.exe
A first chance exception of type 'System.IndexOu tOfRangeExcepti on' occurred in 2nd ind asgmt.exe

now i'm being able to select randomly 6 numbers and display them in the buttons, the bit i can't achieve is to select one number once only which i was trying to do with the boolean array but i'm having trouble to set it up
any help will be so much appreciated
thanks

[Modibbo]

I've been able to achieve what i wanted with the code

Dim x As Integer() = New Integer(10) {}

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

        Dim m_blnUsed As Boolean() = _
        New Boolean(x.GetUpperBound(0)) {}


        Dim objrandom As Random = New Random()
        Dim intrandom As Integer
        Dim index As Integer
        Do
            intrandom = objrandom.Next(0, m_blnUsed.Length)
            
        Loop Until m_blnUsed(intrandom) = False
        m_blnUsed(intrandom) = True


        For index = 0 To 5
            x(index) = intrandom
        Next

        Button3.Text = Str(x(0))

        Do
            intrandom = objrandom.Next(0, m_blnUsed.Length)

        Loop Until m_blnUsed(intrandom) = False
        m_blnUsed(intrandom) = True


        For index = 0 To 5
            x(index) = intrandom
        Next
        Button4.Text = Str(x(1))
        Do
            intrandom = objrandom.Next(0, m_blnUsed.Length)

        Loop Until m_blnUsed(intrandom) = False
        m_blnUsed(intrandom) = True


        For index = 0 To 5
            x(index) = intrandom
        Next
        Button5.Text = Str(x(2))
        Do
            intrandom = objrandom.Next(0, m_blnUsed.Length)

        Loop Until m_blnUsed(intrandom) = False
        m_blnUsed(intrandom) = True


        For index = 0 To 5
            x(index) = intrandom
        Next
        Button6.Text = Str(x(3))
        Do
            intrandom = objrandom.Next(0, m_blnUsed.Length)

        Loop Until m_blnUsed(intrandom) = False
        m_blnUsed(intrandom) = True


        For index = 0 To 5
            x(index) = intrandom
        Next
        Button7.Text = Str(x(4))
        Do
            intrandom = objrandom.Next(0, m_blnUsed.Length)

        Loop Until m_blnUsed(intrandom) = False
        m_blnUsed(intrandom) = True


        For index = 0 To 5
            x(index) = intrandom
        Next
        Button8.Text = Str(x(5))

    End Sub

End Class

i'm having this on immediate window

though at run time i'm still getting A first chance exception of type 'System.IndexOu tOfRangeExcepti on' occurred in 2nd ind asgmt.exe
A first chance exception of type 'System.IndexOu tOfRangeExcepti on' occurred in 2nd ind asgmt.exe
A first chance exception of type 'System.IndexOu tOfRangeExcepti on' occurred in 2nd ind asgmt.exe
A first chance exception of type 'System.IndexOu tOfRangeExcepti on' occurred in 2nd ind asgmt.exe
A first chance exception of type 'System.IndexOu tOfRangeExcepti on' occurred in 2nd ind asgmt.exe
A first chance exception of type 'System.IndexOu tOfRangeExcepti on' occurred in 2nd ind asgmt.exe
A first chance exception of type 'System.IndexOu tOfRangeExcepti on' occurred in 2nd ind asgmt.exe
A first chance exception of type 'System.IndexOu tOfRangeExcepti on' occurred in 2nd ind asgmt.exe
A first chance exception of type 'System.IndexOu tOfRangeExcepti on' occurred in 2nd ind asgmt.exe
A first chance exception of type 'System.IndexOu tOfRangeExcepti on' occurred in 2nd ind asgmt.exe
A first chance exception of type 'System.IndexOu tOfRangeExcepti on' occurred in 2nd ind asgmt.exe
A first chance exception of type 'System.IndexOu tOfRangeExcepti on' occurred in 2nd ind asgmt.exe

i'm more concern about the next stage which i don't have any clue, even how to start
what i want is the first of the buttons containing the selected numbers clicked, the number will be copied in the first of a 6 set of labels and so on.
to be more explicit, the 6 buttons will be clicked one at a time and their content copied in the 6 labels as going; the 1st button to be clicked to the 1st label, so on

[Modibbo]

i've been thinking (may be wrongly & sorry about that incase) there might be a way to set up an array of captions and assign them to the labels and i've been trying hard, but again i have no clue
any help pleasethis what i've been trying to

doDim y As CaptionButton() = New CaptionButton() {}

label1.text="y(0)"

label2.text=y(1 )and i'm getting the error message

Declaration expected

at both the last 2 lines of the code (where i'm trying to assign the captions to the labels

[Killer42]

What about if you just set up a form-level variable to count the number of times buttons have been clicked. Each time a button is clicked (up to 6, or whatever) you add 1 to that counter and use it to decide which label to update.

As for the way you're assigning the values to the buttons, it's good to see that you got it working, but I believe you can use a bit more loop processing to reduce the size of the code considerably. Remember, the basic idea behind a loop is that you should not need to do something more than once. Anything which you are coding repeatedly (for example, your For x = 0 to 5 loop setting up the x array) can usually be done inside a loop instead.

[Modibbo]

thanks once more again for helping, as i was saying i don't have any clue as to how to start, would it be possible to give an example of code please
thanks

[Modibbo]

i've been trying to set up a string array and assign the contents to each of the labels as needed with the code

 Dim y As String() = New String() {}

Label1.Text="y(0)"

and getting the error message

Declaration expected

with a wigly line on Label1

[SammyB]

i've been trying to set up a string array and assign the contents to each of the labels as needed with the code

 Dim y As String() = New String() {}
 
Label1.Text="y(0)"

and getting the error message with a wigly line on Label1

You must have deleted Label1

[Modibbo]

You must have deleted Label1

unless if i don't get you, but i did not delete Label1 as i'm telling you the wigly line is on Label1, so it has to be there to have the wigly line on it

[SammyB]

unless if i don't get you, but i did not delete Label1 as i'm telling you the wigly line is on Label1, so it has to be there to have the wigly line on it

No, it has to not be there to have a wigly line. :D When you hover over the wigly line, what is the error message?