Visual Basic: Random Strings!

	Visual Basic: Random Strings!
	Discussion by ViRuaL with 15 Replies. Last Update: October 18, 2011, 11:24 am

ViRuaL

This article will teach you how to get random strings for output to a label caption, or anywhere you want it to go.

1. First we need to declare our string names:

CODE

Private RndString(2)

This declaration says there will be an array of strings called RndString, and there will be 2 strings in that array.

2. Then, we need to create a function that will generate a random number.

CODE

Private Function RandomNumber(rUpper As Integer, Optional rLower As Integer) As Integer

' Generate random number between upper and lower bound values
Randomize
RandomNumber = Int((rUpper - rLower + 1) * Rnd + rLower)
End Function

This initializes the Randomize engine, then picks a random number between the upper and lower bound values that you specify.

3. Now we need to define our strings. You'll most likely want them to be defined on form load, but if need be you may put them on a button click or something.

CODE

Private Sub Form_Load()
RndString(1) = "Yes"
RndString(2) = "No"
End Sub

This defines our strings for later use.

4. Now let's say you want to change a label's caption when a user clicks a button, to one of the random strings we have previously defined. The code would look something like this:

CODE

Command1_Click()
Dim RndNum As Integer
RndNum = RandomNumber(2, 1)
Label1.Caption = RndString(RndNum)
End Sub

This is where the magic happens. RndNum is used to define the index of the string array, and we set it's value equal to a random number, either 2 or 1. Then Label1's Caption becomes the string index of whatever number was produced from the randomize engine.

All done! If you need help with this code or anything else, e-mail me at ViRuaL@gmail.com

Mon May 16, 2005 Reply New Discussion

Legend

Hey thats nice! Well... I was doing it like that:
I was doing a random number, and then I was saying
If RandomNumber = 1 then
String = "Yes"
ElseIf RandomNumber = 2 then
String = "No"
End If

It's easier your way

Sat Aug 27, 2005 Reply New Discussion

FeedBacker

Hey! nice code, I'm kinda new to VB, I did a little coding on my work experience in school a few months ago and I really liked it. Anyway, want I want to do is to create a program that when a button is pressed on the form, a "random" name or sentence from a database will appear in a textbox or something. I don't know how to do it, so this is why I'm asking :P.

This is an example of something I would like to create: www.factorizer.com

Thank you for your help,
Sam

-SamDave

Wed Oct 17, 2007 Reply New Discussion

FeedBacker

i have a doubt about randomly generating a string
Visual Basic: Random Strings!

I'm writing a code to display 4 options in radiobuttons , that means I have 4 radiobuttons , I want to generate the answer randomly each time different answers but there much be one answer is correct that means that answer will not be randomly generated ..

My question is how to generate the random strings and keep track of one the right answer .. Even that right answer should not be static (it should be every time in different radiobutton) so the person who's answering the quiz will not be able to remember the place of the radiobutton which has the correct answer .
So will you Please tell me how to do that .
The second question is :
If I want to generate random picture in vb.Net .. How can I do that

-noor

Fri Jan 4, 2008 Reply New Discussion

turbopowerdmaxsteel

We can only generate Random numbers within a specified range. However, this number can be used as the index for an array so that we can select a random element from the array, be it an array of Strings, Images, or whatever. What I mean to say is that the process to selecting random picture is the same as that of selecting random strings.

Another thing that I must mention is that this whole stuff we have seen above is not generating a random string, rather selecting a random string. Generating random strings would generate something like zxjhtsjbdjgasd or asdxcbjdkhasd. You can however, select a dictionary word from a list or an array. But, it wouldn't be generating either.

Back to the first question:-

I am assuming you have a collection of wrong answers and a correct answer for each question. (You don't want to make the correct one obvious by filling the wrong ones with those randomly generated strings we just saw, do you?) You need to shuffle the correct answer's position (1, 2, 3 or 4) each time and you need to select 3 wrong answers from the wrong answer collection.

I'll be using the function created by ViRuaL.

STEP 1: First we generate the random position of the correct answer and store it in our variable: Dim CorrectCh As Integer = RandomNumber(1, 4)

STEP 2: Set the correct answer as the text for the appropriate Radio Button: Options(CorrectCh - 1).Text = CorrectAnswer

(Assuming Options to be a zero based array of Radio Buttons)

STEP 3: For each of the remaining positions, generate a random number. Using this number we select a random answer from the list/array of wrong answers and set the text of the Radio Buttons accordingly.

CODE

For I As Integer = 1 To 4
If I = CorrectCh Continue For
Dim Ch As Integer = RandomNumber(0, WrongAnswers.Length - 1)
Dim WrongAnswer As String = WrongAnswers(Ch)
Options(I).Text = WrongAnswer
Next I

Although this code is still not bug free. There's a pretty good chance that the same wrong answer will be repeated. This is because generating a Random Number makes no guarantee that it won't be repeated in the next iteration. To resolve this you can follow either of the ways:-

Method 1

Store the selected answers or their IDs in another array. Whenever a new choice is generated, make sure that this number has not been already generated. If it has been then repeat the process again.

CODE

Dim SelectedWrongAnswers As New List(Of Integer)
For I As Integer = 1 To 4
If I = CorrectCh Continue For
Retry:
Dim Ch As Integer = RandomNumber(0, WrongAnswers.Length - 1)
For J as Integer = 0 To SelectedWrongAnswers.Length - 1
If SelectedWrongAnswers(J) = Ch Then
Goto Retry
End If
Next J
SelectedWrongAnswers.Add(Ch)
Dim WrongAnswer As String = WrongAnswers(Ch)
Options(I).Text = WrongAnswer
Next I

The inner loop can be eliminated by using a HashTable as follows:-

CODE

Dim SelectedWrongAnswers As New HashTable
For I As Integer = 1 To 4
If I = CorrectCh Continue For
Retry:
Dim Ch As Integer = RandomNumber(0, WrongAnswers.Length - 1)
If SelectedWrongAnswers(Ch) <> Nothing Then
Goto Retry
End If
Dim WrongAnswer As String = WrongAnswers(Ch)
SelectedWrongAnswers.Add(Ch, WrongAnswer)
Options(I).Text = WrongAnswer
Next I

Method 2

This Method is not quite efficient, because the Retry operation may take many iterations if an already generated random number is being generated again. So a better approach is to use a class that generates a non random number. You can find the VB .NET and C# . NET implementation of such a class at http://maxotek.net/blog/?p=9

The following code uses the RandomNumber class declared at http://maxotek.net/blog/?p=9

CODE

Dim WrongAnswerGenerator As New RandomNunber(0, WrongAnswers.Length - 1)
For I As Integer = 1 To 4
If I = CorrectCh Continue For
Dim Ch As Integer = WrongAnswerGenerator.GetRandomNumber()
Dim WrongAnswer As String = WrongAnswers(Ch)
Options(I).Text = WrongAnswer
Next I

Sat Jan 5, 2008 Reply New Discussion

Chesso

I have not done VB in a long time, but I assume you can make object arrays (filled with strings and what not), or record arrays maybe.

Use that instead of if/then/else if, and if you have something available like record arrays, add an extra value for primary (or the answer), so say if you load 4 strings from file, 1 will be marked in some manner as the correct answer, mark it as primary.

Then if someone checks a box, check the correspendence between radio button and record array, and check it's primary property to see if it's the correct answer.

Anyway, I do all this stuff in Object Pascal (Delphi), but VB should have something.

Sat Jan 5, 2008 Reply New Discussion

FeedBacker

Word (Integer)
Visual Basic: Random Strings!

I am currently trying to make a spelling program in which it has 3 levels .
What I'm stuck at is when it comes to coding it how do I get it so words are shown on a label then took off in which you can then right in the text box what word it was. How do I then have random words come up but not have them show again so that the person isnt seeing the same word over and over again.

-question by Paul

Tue Feb 26, 2008 Reply New Discussion

turbopowerdmaxsteel

You need to generate non-repeating Random numbers. I made a class for the same which can generate non-repeating Random numbers within a specified range or select a non-repeating Random number from a supplied list of numbers. The numbers will be repeated after a complete cycle finishes and all the numbers have been generated once.

You can find the VB.NET code at http://maxotek.net/blog/?p=9

You could modify the code a bit to directly select one of your words stored as string types.

CODE

Public Class RandomNumber
Dim WordDomain As New ArrayList ' The Words to be generated
Dim Words As New ArrayList ' The Words waiting to be generated

Sub New(ByVal ParamArray Words() As String)
' Words in a Param Array
Dim Word As String
For Each Word In Words
WordDomain.Add(Word)
Next

AddItems()
End Sub

Sub New(ByVal Words() As String)
' Words in a String Array
Dim Word As String
For Each Word In Words
WordDomain.Add(Word)
Next

AddItems()
End Sub

Private Sub AddItems()

Words.Clear()
' Insert All Words Into the Array
Dim I As Integer
For I = 0 To WordDomain.Count - 1
Words.Add(WordDomain(I))
Next
End Sub

Public Function GetRandomWord() As String
If Words.Count = 0 Then
' Re-add the Items, when all the words have been generated.
AddItems()
End If

' Return a Random Item and Remove it from the List
Dim Ch As Integer

' Using Timer as the seed for the Random Number Generation
Randomize(Microsoft.VisualBasic.Timer)

' Random Number is generated within the range.
Ch = 0 + CInt(Rnd() * (Words.Count - 1))

Dim Word As String = Words(Ch)
Words.RemoveAt(Ch)
Return Word
End Function
End Class

The above code generates Random words based on a supplied list using a String array or as a ParamArray.

Wed Feb 27, 2008 Reply New Discussion

FeedBacker

random function using in automatically selected question in vb 6.o version
Visual Basic: Random Strings!

Replying to Feedbacker you have a query of question and this query is selected by using random function.

-question by santu

Fri Mar 14, 2008 Reply New Discussion

FeedBacker

[Replying to turbopowerdmaxsteel,5264,119 669] I tried to use the code you wrote but I get an error on the word New after the Sub New. I have tried several corrections but can't figure it out. What I really want is a way to have a list of 12 or 16 names that can be randomly sorted for a game, so that partners will be different each month. I wrote one in Quick Basic and it worked great but programs written in QB can't be printed through Windows. I would really like to find a way to make one in vb2005Express.

-question by JRichards

Tue Apr 15, 2008 Reply New Discussion

FeedBacker

help with selecting random pictures
Visual Basic: Random Strings!

Please could someone help with the following question

I'm new to VB and need help, My problem is that I need to know how I can write the correct code which enables a button when each time it is pressed, it randomly selects a picture from 6 different pictures and show this on the screen. The pictures are bmp and would be stored on the pc - I have for now put them in c:pictures location with the file names 1.Bmp 2.Bmp etc...

I am unsure how to write the correct code to select the pictures at random from the file.

-question by steve

Sun Apr 20, 2008 Reply New Discussion

(G)nick

i want to use this concept but as something differentVisual Basic: Random Strings!

okay I want to make it when you enter a name into a text box it displays that name but after that it displays one of to random phrases such as for example if they put in cody it would return cody and then randomly choose between "is cool"or "some thing else"

-reply by nick

Wed Dec 10, 2008 Reply New Discussion

(G)Sherri

Listbox with random string Visual Basic: Random Strings!I'm trying to create a program that is a contest. Where you enter names in a input box and they are stored in the listbox. After the names are stored, you click a button and it picks a name at random from the listbox and displays the winner's name in a label. Any ideas?-question by Sherri

Thu Nov 19, 2009 Reply New Discussion

(G)jerome

I'm currently in need of a program for my project...We're to interface a circuit via VB... We know what we want to happen on our program yet we don't know how to encode it already in VB... This is how the program goes...FOR EXAMPLE.. There are THREE set of numbers... And inside those sets were numbers stored...SET I = 1-10SET II = 11-20SET II = 21-30(the numbers inside the sets are just examples... We'll be using Input Values from a Parallel Port/Printer Port... -thinking that using other numbers would affect the changes in the program... But I don't really think so... Anyways...)Upon loading the form... The program will randomly choose one of those sets... After that... The user will input the values inside the chosen set respectively and correctly... I.E... The program randomly got SET II...In a label box... The values 21-30 should show in it respectively( the values are inputted to the label box through text box and a command button)... If it goes wrong... It will automatically terminate the program... Otherwise... A message/event will happen that the values are properly and correctly inputted... I hope you get what I'm actually saying...-reply by jerome

Sun Oct 2, 2011 Reply New Discussion

(G)Jerome

-reply by Jerome

Sun Oct 2, 2011 Reply New Discussion

(G)Hemanth

Random ElementsVisual Basic: Random Strings!

Hello there..I want to generate random elements of a string that is in a string array.I.E.. Elements of newyork fromDim cities() As String = {"delhi", "pune", "goa","newyork"}Should be displayed at random..Followed by other string array elements..Please help me out..:)

-reply by Hemanth

Tue Oct 18, 2011 Reply New Discussion