NullReferenceException For A Class Array
Mar 23, 2010
I'm pretty new to VB.NET (VS 2008) so I apologize in advance if my problem is very basic.
I have defined several public arrays with fixed dimension is a public class:
Code:
Now in the main class I'm declaring two global variables:
Code:
I can then redim "parent2.V()" without problem.
Everything works fine with "parent1" but "parent2" gives me a NullReferenceException when I try to read/write from it. Troubleshooting tips tell me "Use the 'new' keyword to create an object instance" which is what I did. How to declare that array "parent2"?
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Feb 2, 2012
I have a class with a subroutine as follows:
Public Sub SetPermissions()
If IsNothing(HttpContext.Current.Session) Then
Exit Sub
Else
[code]....
I know that my session variable is not yet set, hence a null value, that's why i'm trying to handle it with IsNothing, but my code still bugs out on me.
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Jan 25, 2011
I am able to query/read the event log using VB.NET 2005 (Win XP). But still I have a problem reading the "Message" / "description" of the event log.I am getting a System.NullReferenceException while reading the "Message" / "Description" of the event log.Also when I use System.Diagnostics.EventLog and read all the Event on by one I am able to read the message/description of the event. This is the code:
Public Sub ReadEvent()
Dim iCount As Int16
Dim PastFourHours As Date = Date.Now.AddHours(-4)[code]......
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Oct 19, 2009
The code below is used to check if the application setting, an arraylist is populated or not via the count method.
When running the program fails with error "NullReferenceException was unhandled" as initially the setting (arraylist) will contain no values.In similar circumstances I would declare a new instance of the object or set value to string.empty or check if DBNull.
I know application settings have a save method but to reference/load them one is not needed.I also left the value field in the projects -> settings to be empty.[code]...
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Jan 27, 2011
I'm getting System.NullReferenceException error when I try to add the employee info to the Employees list.
[Code]...
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Feb 18, 2010
This is my code:
Public UserBookings() As String
If dr.Read() Then
Dim intCounter As Integer
[code]....
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Jun 21, 2010
I am trying to create an list or an array of a class.Here is my "Ingredient" class that I am trying to create a list of:[code]In my "recipe" class, I am want to create a list (or array) and I am drawing a big blank on how to do it. Can anyone point me in the right direction?
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Jul 26, 2011
I'm designing a small GUI Windows program that allow staff at a cinema to reserve seats for customers. There will be a total of 60 seats in the cinema. I have two classes in my program:-
1.) MainForm.vb - used for I/O actions and user interaction
2.) SeatManager.vb - used to hold and handle the background methods and functions that make the program work
Here is the code for my MainForm.vb class thusfar:-
Public Class MainForm
Private Const m_totalNumberOfSeats As Integer = 60
Private m_seatManager As SeatManager
[Code]....
Basically, when the program opens, the lstReservations list in the MainForm class will be populated with a total of 60 (m_totalNumberOfSeats) entries to represent 60 seats. Each of these seats will contain the index number from the array m_nameList; this index number (+1) will represent the seat number and then in the lstReservations list, after the seat number, I'd like it to contain the respective entry from the m_nameList array. As all entries will be held in RAM, when the GUI is opened, all m_nameList array entries will be empty. As the user uses the program, they can highlight a row in the lstReservations list and then use the GUI textboxes to enter the customer's name which will then be populated into the respective array entry.
how to, when the GUI opens, ensure that the lstReservations list takes all of the blank entries from the m_nameList array and from there, I can highlight a row to carry out further methods on?
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Sep 9, 2010
I want to reading in a excel file and extract the sCodenumber sDescription ans the sStatus and store them in a array : StatusComposeArray(5200) As MyCompose. After this I need this array for comparing outside this class. But as can you see the array is defined inside the sub: ReadingIn_ExcelFilesCompose [Code]
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Jun 22, 2010
A c# class's single dimension byte array contains socket level instrument sensor data as per:
public static byte[] frameData
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Jan 20, 2009
It's been a LONG time since I messed with VB, and I'm messing around with VB 2008 now.I'm trying to make a custom class with three variables,
ID (String)
Title (String)
Comments (Array of String)
[code]......
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Mar 12, 2010
What is the difference between using the 'array' class in VB and just declaring an array like normal. In other words, what is the difference between:
Dim numOfTicketsPerDay As Array
Dim intNumOfTicketsPerDay(6)
As Integer
Is there any preference of when one should be used over another?
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Mar 15, 2010
If I make the following array in a push button event and I want to put those array variables in a class array. How do I do that? I am just beginning to learn about classes in vb.net but I am having problems using classes and arrays.Is there any good tutorials on that subject.
[Code]...
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Jun 3, 2011
I'm designing a small GUI Windows program that allow staff at a cinema to reserve seats for customers. There will be a total of 60 seats in the cinema. I have two classes in my program:-
1.) MainForm.vb - used for I/O actions and user interaction
2.) SeatManager.vb - used to hold and handle the background methods and functions that make the program work Here is the code for my MainForm.vb class thusfar:-
[Code]...
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Nov 3, 2011
I have main class of Races with mulitple properties. One of those properties has been defined as another class Runners.
So I have a race with multiple runners and when I try to update the data i get an instantiation error.
For the life of me I can't get it to work.
This is what I am trying to do...
In the clsRace class I have defined :
PublicProperty clsRunner(ByVal index AsLong) As clsRunner
Get
[Code].....
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Feb 28, 2012
I am New to <acronym title="Visual Basic">Vb</acronym>.Net. this is my first test. i try to create small address book. but i don't know what wrong. it compile perfect but when it run it give error and not work. is there any other way to add same class like in class inside array?
[Code]...
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Jul 28, 2010
I have two classes, and for a property in one of the classes I'd like to be able to load it up with an array of the other class. However my attempt at accomplishing this results in a "Object reference not set to an instance of an object" error. I know it's a rookie mistake, but I'm stumpedssist?
My code is as follows:
Namespace Parking
Public Class garage
[code]......
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Aug 6, 2011
I want to include Arrary of Class in a class. For Example
Public Class AddressSet
Private addressValue As String
Private effectiveDateValue As Date
[code]....
my goal is let the user add address maximum 10 addresses under one name How do I implement "Property" to have array AddressSet using array index?.
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May 8, 2012
In short, I can't seem to get the xml serializer to serialize an array of one class type embedded within an array of another class.I have two classes, one of which contains an array of the other class, as follows (there are other objects in the classes that I've not included):
[Code]...
There must be a simple way to get the XML serializer to serialize the array of the class embedded within the array of the class that I am serializing. Am I missing something?
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Jan 31, 2011
I want to create a custom class that has inside an array of another custom class (see my code below) but when the programm runs is crashes. Why? What is the right expression???? Plz help I'm a newbie in VB.net.....
Public Class ctrarray
Public nameclass As String
Public ctrlindex(glvar_spaces) As ctrlindexclass
End Class
[code]....
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Oct 7, 2011
is it possible to make a class I made act like an array? Or is there a better way of doing this?
Example:
Namespace Animal
Class Dog
Public Name As String
[code]....
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Dec 19, 2010
like every class in .net does Arrays also inherit Object?
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May 14, 2010
I created a simple Class called Student.[code]And then I tried to create an array of Students called s. I'd like to do something simple with the names of one of the students like the following..[code]I know that I need to use the New keyword to create an instance for each s(), but I'm not sure where to put it. When I try it without the array it's easy.
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Mar 18, 2011
why this sub show me -3?
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim s As String() = {"0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "10"}
[code].....
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May 24, 2010
Public Class qqq
Public xxx as string
End Class
[code].....
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Dec 20, 2011
I have done developments using class module and property. I have done the deceleration as follows in VB6.
VB6 deceleration
Public BomMatList() As New MaterialList
After this deceleration i use BomMatList as array as follows
BomMatList(I).MatDescription = "New Material"
I can execute this statement on a for loop and change the value of "I" to increase the array size. How can i do the same in Visual Studio 2010.
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Aug 12, 2009
I'm writing a ray tracing program that uses snell's law to trace rays through a system of lenses to examine abberations in a given design.I have a class called lens, which holds variables for example, name of the lens, description, number of elements.I want to be able to have a sub class or array within lens (or some other way to manage this data).I wont know what number of elements is until run time.
So I would need to define the array at run time.Part of the idea of my program is randomly generate lens elements within given rules (as in a massive lot), keep the top designs and continually refine them by making billions of micro adjustments to the variables that define the lens etc, which I can pick up later on as it'll save the database/variables.For example, say Lens(63).NumberOfElements = 6.
I want to be able to access Lens(63).Element(3).Radius1 Etc, there will be a bunch of variables under Element, such as Radius1, Radius2, refractive index, horizontal diameter, vertical diameter, and spacing between the next element if it isnt the first.
And Lens(70) may only have 4 elements etc. How can I define a different array size like that in the class under different parent array indexes at run time?
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Jan 15, 2012
How can I create an array of a class that I have declared? I have this class named partswith properties of frame, engine and date, and i want to know how could I store them in an array .
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Jun 21, 2010
I could have an array of players but I cant dim and array as new and my players are all a class I made called gameobject
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Nov 21, 2009
I want to modify the base Array class by creating a new class called "FileArray".I have some text files that are read into a string array. Each element in the array is a line from the text file. I want to update the GetValue method by overloading it or overriding it so that it will update some value that will give an indication to what the last line was. I have a couple of ideas on how I can do this:
1) Use a public integer, like intLine, that gets updated everytime GetValue is called.
2) Create a new property of Array, such as "LastLine" that would return the last line number (which would basically be the last index value +1) and then use a public array to store the files (though this is less desirable as the array may be used by several different functions)
An easier way would be to be able to determine the last element that was returned, which is basically what I think I am describing above.
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