Multiple Choice Quiz With Access, Null Reference?
Jul 16, 2009
I have a button 'start quiz' which uses the dataset to fill the quiz form - ready for the user to start answering the questions.However, I am getting a 'null reference' at the point where the 'navigate records' on the quiz form is called. Have looked up that it means I have a variable that is null. But I have declared all the variables etc. Not sure what I'm doing wrong. I am very new to programming and I have spent quite a bit of time on this already.This is the code for the student user login:
Private Sub btnLoginStudent_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnLoginStudent.Click
FrmQuiz.Show()
[code].....
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Nov 22, 2011
I am working on a multiple choice quiz, admin screen, student login screen where they choose their level of difficulty. I have been able to start the quiz, have the questions and answers filled, user answers question, check if correct or not, if correct then the score is incremented.I am able to set up a variable for 'level' and want to write some code so that whatever is selected then that table / questions will be selected and displayed to the user.
The way I'm thinking at the moment seems very long winded. I think I'll have to write an IF ELSE statement/case statement for each of the 'navigaterecords' and the sql statment for beginners, intermediate and advanced.Assume there is a variable 'LEVEL' - have not actually done this yet. Where the code refers to 'advanced' is where I have been trying it out to select questions from the advanced table.
Imports System.Data
Imports System.Random
Imports System.Data.OleDb
[code]....
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May 10, 2009
I need a multiple choice quiz but I've ran into some problems. So far i have 5 arrays: one for the questions and four for the answers. The question is displayed in a label and the answers on radio buttons. Problem one: I am using a random number generator to pull them but this allows them to be reused. How do I stop repeats. Problem two, my grading isn't always working.
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Jan 22, 2011
I have to make a multiple choice and true or false quiz in VB. So i am thinking of two questions on one form.BUt i have to make the questions appear in random and not in order and make sure they dont repeat.Btw, i have searched a long time for this. I have found out how to make random numbers. But I have to make sure only 10 come and not repeated.
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Mar 4, 2011
trying to make a Multiple Choice quiz, with 20 questions
-4 RadioButtons
-2 Label (Reading the Questions) and 1, keeping a score count
Do I wanna make some arrays like Questions(20) and Answers(20)
Dim ScoreCount as Integer
So I want it to be a little screen, and once you click a Radiobutton to choose answer, it will change the label to Question(2) so forth.. but I am unsure how to do this. I am fairly new to vb, im doing this to learn.How do I make it so everytime you click a radiobutton wether it's right or wrong, the next question and possible answers all change??
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Apr 22, 2011
I am using KeyPressEventArgs to restrict several text boxes to numeric entries only. Rather than repeat the code, I thought I would make a "RestrictToNumeric" subroutine and call it from each "KeyPress" event. Like So:
Private Sub txt1_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles txt1.KeyPress
RestrictToNumeric()
End Sub
[code].....
The problem I am encountering is that the variable 'e' is used before it has been assigned a value, causing a null reference at runtime.
So I tried to add Dim e As System.Windows.Forms.KeyPressEventArgs As?to the RestrictToNumeric sub.I cannot figure out what I need to "Dim" it as...
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Dec 15, 2011
I have a fairly simple piece of code:
Private _PurchaseDelivery as PurchaseDelivery
Protected Overrides Sub InsertItem(ByVal index As Integer, ByVal item As PurchaseDeliveryItem)
[Code]....
Which is inside a class which overrides a custom list base. The code is occassionaly throwing an unhandled exception, System.NullReferenceException, on this line when used in production:
If _PurchaseDelivery IsNot Nothing AndAlso _PurchaseDelivery.DefaultSKUBinID.HasValue Then
DeafultSKUBinID is declared as an Integer? (Nullable Int) in the PurchaseDelivery class. I cannot see what might be causing this error, why would this be returning an error?
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Aug 11, 2009
I have created my own quiz for my aplication, but, a lot of people asked me , why can't the programe count right or wrong answers and one of them told me can you make a quiz that randomly selects questions?ok, I told them its all posible to make , but I actually coulndt make it working.So, usualy for a classic quiz I got the code to make a button go red if the answer is wrong, but I need the code line for the random question selection and the counting.I found some code but it didn't work,
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Feb 24, 2009
I'm not great with VB and I'm having some trouble with my University assignment at the moment.I'm trying to code a multiple choice program with several forms with different questions and then a scoring form
I'm not sure how to tell VB what the correct answer should be and how to display the scores in another form, the answers need to show how many correct in each section out of how many the user attemped to answer, so they can check scores before completing all the questions.
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May 13, 2012
I'm currently quite new to VB and am trying to create a multiple choice questionnaire for work. This is a depression survey in which there are 23 groups of statements with 4 options per group. Every time a patient clicks an option, the next set of 4 questions comes up on the screen.
I'm trying to convert the old VB4 code into the new VB 2010 code. Before we were using a control array and the code looks a little something like this[code]...
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Nov 3, 2011
I am in the process of creating an array for a set of multiple choice questions but I am having a few problems. I am an absolute beginner at VB and I am creating a quiz that users will select one of three possible questions and then depending on their answer a +1 value will be added to the score. However I do not know where my questions and answers are supposed to go, from what I have read online I have to use (0, 1) format to give possible answers but I do not know how I would make the questions and answers display in textboxes on my form. At the bottom of my code I have also included code to randomise the questions although I am unsure as to if it is correct. At the moment I can run my form fine without any problems but my main issue is to how I will get the questions and answers linked to my textboxes on my form.
Public Class frmTest
Private ran As Random = New Random()
Public intScore As Integer
Private Sub cmdStart_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdStart.Click
'Turns the message box invisible when start is clicked
lblMessage.Visible = False
[Code] .....
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Apr 3, 2012
I am trying to create a simple program that delivers True/False questions from a text file and then displays the mark to the student, but I'm running into trouble.I created two forms. The first contains a listbox which is populated with the possible test choices (taken from a .txt file containing only 2 choices). I wrote this code for the listbox
Private Sub frmTest_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
'Populates listbox with test names from TESTS.txt
Dim sr As IO.StreamReader = IO.File.OpenText("TESTS.txt")
lstTest.Items.Clear()
[code]....
After the test is chosen, the user presses BEGIN. At this point I have my actual Question form pop up, and the first form is hidden. I tried to begin with an If-Then statement which will open the appropriate .txt based on the selection from the first form.
Private Sub frmQuestion_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
'Opens appropriate test based on selection
If frmTest.txtChosenTest.Text = CStr(frmTest.lstTest.Items(0)) Then
[code]....
This is where I get completely bottle necked though. I've been staring at the screen/textbook for 5 hours now and I don't understand how to write the code that will take my questions from the (now open) text file, separate the question from the answer, and put the question and question number in the appropriate text boxes. The format of the question .txt's are simple. One question per line, with the answer following, separated by a comma. For example, Midterm.txt might look like this
Question1isthisone,T
Question2isthisone,F
If I were to design a form for this problem let's say it would look like this:I am currently stuck at this part though. How do I populate the two read-only text boxes with the question number/question, and then cycle through the questions from the .txt while also keeping the user's score?
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Mar 12, 2010
I have four drop down lists here and I've assigned the datasource and displaymemberproperties so they are populated by a table. When I run the program and select a choice, all four of them get updated with the new choice.
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Nov 28, 2009
I am struggling to write code for single-answer multiple choice tests (i.e. Choices A, B, C, D).
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Jun 2, 2010
This is related to my previous question but it is a different problem.I have two classes: Server and Database.
[Code]...
The problem is in the LoadTables in the Server class. When it hits Databases.Add(db) it gives me a NullReference error (Object reference not set). I don't understand how it is getting that, all the objects are set.
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Jun 24, 2010
I have some code which gets child items for a menu via the GetChildren function which takes a list of menuData: Dim builtMenu As New List(Of MenuData)(_rawData.FindAll(Function(item) item.GroupingID = 0))
For Each menuData As MenuData In builtMenu
If menuData.Children IsNot Nothing Then
menuData.Children.AddRange(GetChildren(menuData))
End If
Next
If I check if menudata.children isnot nothing, it always is nothing because the GetChildren function is yet to run (providing the child items, which do exist). If I remove this check and just have this code:
Dim builtMenu As New List(Of MenuData)(_rawData.FindAll(Function(item) item.GroupingID = 0))
For Each menuData As MenuData In builtMenu
menuData.Children.AddRange(GetChildren(menuData))
Next
Then I am presented with a Object reference not set to an instance of an object error on menuData.Children.AddRange(GetChildren(menuData))
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Jan 8, 2011
I have been trying to use sockets in VB.NET and once I cannot understand how to avoid a null reference. [code] I have tried introducing sock as 'New Socket', but this gives me 'Overload resolution failed because no accessible New can accept this number of arguments'.I also cannot simply add '= Nothing' onto the end of my declaration since this still gives a null reference.
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Jan 29, 2011
I'm practicing on this one, and I know it would be better to just use a string variable instead of a class. I have another working program using a string variable, but on this one I wanted to make it use an array of class objects.
I keep getting null reference exceptions at the line where the object is assigned the textbox text.[code...]
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Dec 16, 2010
How do I check for a null object in a subroutine handle?
Private Sub Form1_KeyDown( _
ByVal sender As Object, _
ByVal e As System.Windows.Forms.KeyEventArgs) _
[code]......
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Mar 21, 2011
I have a null reference warning. Dummy code as follows:
Dim poo As IEnumPooTypes
Toilet.GetPooInBowl(poo)
The variable 'Poo' says it may result in an object reference not set error but I cannot use the 'New' keyword with an instance. How do I make the warning go away?
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Jun 27, 2012
visual basic application prompting me a message "Object reference not set to an instance of an object". i have 2 project in one solution. One is developed in c# and other is in vb. i am calling a method of c# project in vb project. the vb code is:[code]when i debug vb project individually it works properly and when i call vb application from c# application, it prompting error. is i missed out any .net framework reference? [code]
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Jan 4, 2010
Im trying to write code that will insert 'records' into an xml file, but everytime i click the button to make the changes to the XML file, it throws a null reference exception, ive gone through this code must be 100 times and cannot find what needs to be declared as 'new' as i know nodes can't be 'new' and the doc is 'new'
Imports System.Xml
Public Class frmuseradmin
[code]......
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Jul 26, 2011
My site has been running fine for sometime now until recently I see in the event viewer a null reference exception in the DNN core:
DotNetNuke.Common.Globals.GetStatus() in
F:BuildsMaintenanceWorkingDirectoryLibraryCommonGlobals.vb:line
1125 at DotNetNuke.Common.Initialize.InitializeApp(HttpApplication
app) in
[code]....
the line 1125 is:
_Status = UpgradeStatus.None
Which is a property of the Globals class and an Enum Also when this happens it doesnt just do it once then sort its self it does it roughly every minute for an hour or so.I made sure all dataprovider.instances are either in a using or a try catch finally or self closing(if the reader is not used)?
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Mar 7, 2011
I have the following code, which is meant to loop through a list of CheckBoxes and if checked if gets the text contained in the linked textbox through the tag of the Checkbox, i have used it before and it worked fine but this time i am getting the following error:
Null Reference Exception was unhandled
Dim DisCheckBox As CheckBox() = {chk0_6, chk6_12, chk12_18, chk18_24, chk2_3, chk3_4, chk4_5, chkXSB, chkSB, chkMB, chkLB, chkXLB, chkS, chkM, chkL, chkXL, chkXXL, chkXXXL, chkXXXXL, chkW8, chkW10, chkW12, chkW14, chkW16, chkW18, chkW20}
For Each Chk In DisCheckBox
[code]....
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Jun 13, 2012
I know I'm being an idiot here and I just can't work it out. But i'm trying to take some data back from a vb.net database. It's falling over with a Object reference not set to an instance of an object error. And before the code runs it's saying the variable is being used before it's set, but I can't see how. Code:
Private taNotifications As dsDataTableAdapters.NotificationsTableAdapter = New dsDataTableAdapters.NotificationsTableAdapter
Dim notification As dsData.NotificationsDataTable = taNotifications.GetDataByClientID(userrow.UserID)
If notification.Rows.Count > 0 Then
Dim notificationrow As dsData.NotificationsRow
Dim forwardURL As String = notificationrow.ForwardLocation
End If
It falls over on the Dim forwardURL As String = notificationrow.ForwardLocation
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Feb 24, 2010
P/Invoke on x64 null reference exceptions, I get null reference exceptions when I try to compile for x64 in .NET code that makes use of platform invocation services to call unmanaged code in dlls. Am I missing something obvious here?
[Code]
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Jul 19, 2009
I keep getting a null reference exception w/this program, and its on the line that declares the array. I've looked it over and over and I just don't see why... Can you let me know if you see anything obvious? I'm also getting an "index out of range" exception, but it looks right to me...I declared everything with an 11 for 12 months, 0 to 11 for the intcount.
[Code]...
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Nov 21, 2011
I'm having this exception while trying to get the value of a cell from a table.[code]...
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Oct 23, 2009
If Not obj is Nothing and obj.IsActive Then ' null reference exception??constructions like this in C# works, because obj.IsActive is not checked if the first condition is false...
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Apr 4, 2011
i have this sql transaction i am using to make sales.But when ever i run the code it give me this null reference exception.I do not really know what is wrong.
[Code]...
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