.net - Get A Class Property To Be A List Array?
Oct 14, 2009
Stack Overflowers:I have been racking my brain trying to get an List(of T) type array to be the property of a class. I know there has to be a simple way of doing it and I can't find a good example on google. Everytime I create a class that I think will work I get the "Object reference not set to an instance of an object" error when I try to use it. My thinking now is that I cannot use it in the way I was hoping to. Here is my latest attempt:
Public Class Item
Private _itemno As String
Public Property ItemNo() As String
Get
[code]....
View 2 Replies
ADVERTISEMENT
Apr 2, 2010
I'm looking for a tutorial on how to Adding a list(of Class) or Collection as another Class's Property.What I am after is something like the Columns Collection for the DatagridView control.I would like to add Items in the graphics screen. Where the item list is displayed in the left panel and the selected Item properties are displayed in the right panel.
View 4 Replies
Oct 19, 2010
I have a base class (ex: Class1) containing a list of another base class (ex: ClassA). Each child class of first base class (ex: Class1AA, Class1AB,..) containing a list of child class of second base class (ex: ClassAA, ClassAB,...)The client must never know which child class is using, then i don't think i can use generic for my bases classes.I try something like this and many more, but i always received errors..Imports System.Collections.Generic
[code]...
View 1 Replies
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?
View 2 Replies
Apr 2, 2010
This is another continuation of an issue with a List(of T) as a property of a class.Following the excellent advice of AtmaWeapon and others on this forum, I have my classes working fine except for something that is inexplicable to me.I initialize my "course" class at a public level in a module. This is so the data in the class will be available program wide and for the application's lifetime. "Public newCourse As New Course".I initialize a local instantiation of the class TimeTable as newTimeTable [code] This issue is: The List(of T) is populated with data, however, when the loop finishes, what I have is the last set of values repeated "X" number of times in the List instead of the data being different in each element of List( Of T). [code]
View 2 Replies
Oct 8, 2010
I have a class called Questions. This Questions has properties QuestionID and QuestionAnswer. My list of Questions has QuestionID like 2, 3,4, 15, 12, 24,22,,,, etc.I need to sort this List of Questions Object based on QuestionID and store in another Questions object.
View 2 Replies
Oct 4, 2011
I have the following class:
[Code]...
I could be way off here, but it almost seems like ID.IDlist points to the address of mylist and so when mylist is cleared so is ID.Idlist. It seems as though the reason the second block of code works is because I am creating a new list in memory for each ID object and ID.IDlist just points to it... is that right?
View 2 Replies
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]......
View 2 Replies
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]...
View 5 Replies
Nov 3, 2009
I have created a class that contains a property array, but I cant use the setters and getters.
[Code]...
View 2 Replies
Feb 6, 2012
I need to define a property in my class which is an array (of doubles).My original (bad) version is this:
Public Class Market
Property Correlations0 As Double
Property Correlations1 As Double
Property Correlations2 As Double
[code].....
This however doesn't work. I get an error already at design time: "Public Property Correlations as Double has no parameters and its return type cannot be indexed."What should I do with it? I also do not know in advance how large the array should be (the array size is determined at runtime based on other properties).
View 8 Replies
Mar 12, 2011
I have a file name that is found at multiple paths. I want to present this data to the user in the format of a DGV. I have a DGV with one text box column for the name, and another combobox column for the paths. I am having trouble getting the combobox column to bind to the property of the class that returns the paths.
[Code]...
View 1 Replies
Jan 5, 2010
I am trying to create a property of type string array (if this is possible).....and I seem to be lost.
I tried the following, but it says "String cannot be converted to '1-dimensional array of string'" at the return
Private _strZipList As String()
Public Property strZipList(ByVal i As Integer) As String()
Get
[Code].....
View 10 Replies
Nov 29, 2011
Is it possible to create a user control with a list of custom class type property? If it is, how can I? The issue is that, in designer mode the property is not displayed in property window. I can add the list on markup but when i switch to the designer mode it gives an error which is 'The user control does not have a public property named BookList'.
View 1 Replies
May 27, 2012
I have a program that will compare an array of grocery list items glist and an array of coupon item clist.When I compare the two and if there is a match somewhere in the array I want to have a picturebox visible.When there is no match, I want the picture box not to be visible. [code] The code seems to work great until I come to the else statement.When the code finds a match it displays the picture box and the msgbox without error, but as soon as the message box is cleared, even though i've input it as an ELSE statement, the picturebox goes false again.Does anyone have any idea of how I can "hold" the picturebox to stay visible while the match between the arrays exists?
View 18 Replies
Oct 20, 2010
In my application I have a class called "RCategory" as illustrated here:
Public Class RCategory
Public Property RCatNum As Integer
Public Property RAct As Char
[code]....
I'm trying to add to my list using the following code:
For ct As Integer = 1 To 8
Dim c As New RCategory With {.RCatNum = ct,
.RAct = dr("RACT" & ct.ToString).ToString,
[code]....
I'm getting an error when I get to the bottom line, though...when I actually execute the RCat.Add(c),I get a System.NullReferenceException was unhandled by user code Message=Object reference not set to an instance of an object. What must I do to be able to use a List (of T) in my class?
View 3 Replies
Jun 1, 2012
I have a very simple class that holds a few public properties - ID, Text, Colour, etc. and a Boolean called 'SelectedItem'. Just like the Checked property on RadioButtons, only one item can have its SelectedItem property set to True within a particular group. Note: there will be several separate groups (lists), each allowed to have only one item with SelectedItem = True.
My first thought was that I would probably just have to handle everything outside of the class, setting SelectedItem to False for every other item in a particular list when another item was selected. But that seems rather inelegant to me. So I've been trying to think of how this might be done within the class. For example: could I perhaps have a private string property called say "GroupName" - set in the New sub when adding a new instance of the class - and then use a private shared method to set every item's SelectedItem property to False, provided the item has the same GroupName as the newly selected item? I would have a go at doing this but I have no idea how to enumerate every instance of a class from within that class, or whether that's even possible. Is it? Or is there another (better) way to achieve my goal? Here is a cut-down version of what I've got so far:
Public Class ResourceItem
Public ID As Integer
Public Text As String[code]....
As can be seen: instead of instantiating a new ResourceItem and passing that as an argument to the manager's Add procedure, I'm simply passing the details of the new item and the procedure is creating the item from those. I don't know whether this is a good or bad idea - please advise - but I've done it because I couldn't figure out how to make the SelectedItem property only writeable by the manager, so I wanted to avoid having directly accessible objects that could have their SelectedItem property set to True without it deselecting all the other items in the same group. Of course that still leaves the possibility of setting a variable to one of the manager's list items and setting it from there, so I would still like to know how I could prevent that, if possible.
UPDATE: I didn't use the code above in the end, deciding instead to go with Cyborgx37's solution - which seems to work perfectly well for me despite the warnings about best practice. I also realised I would need to use the same class in another scenario where multiple items could be selected, so it was easy to add a Boolean property to the manager to enable that.
View 2 Replies
Feb 21, 2011
I have the following property in a property grid in VB.Net 2010.
<Description("Rapid Entry Post Car Wash Settings CarWashOptionPushButtons"), _
Category("Post Car Wash")> _
Public Property CarWashOptionPushButtons() As String
[code]....
I need to make this property a list box that gets the values from a database table and populates the list box with the values from the table. I have tried numerous things to no avail.
View 4 Replies
Aug 13, 2009
I have the following code:
Public Class MyColorsClass
'Constructors
Public Sub New()
'Empty Constructor
[code]....
However, if the empty constructor was called to instatiate this class then the colortype is not yet set. Therefore, if one accesses the 'IsColorCool' property it will always return 'False'. Now for the sake of this example, I must keep the empty constructor as part of the class.Now I could add some code in the 'IsPropertyCool' to check and see if a ColorType has been defined, and throw an exception if it has not been set, but I don't really want to do that.I also could always move the logic OUT of the property and into a method on the class called 'DefineIfColorIsCool' or something, and make the owness on the caller to make sure the method was called if they want to use the property 'IsColorCool'?
View 5 Replies
Apr 7, 2011
Supose a base class
Public Class airplane
Private var_num_seats As Integer
Private var_num_engines As Integer
[code]....
Obviously, I don't wish that the class Glider has the method "start_engines" neither the property "num_engines". Otherwise, other child classes may have. How can I supress these property and method in child class, not just ignoring (if I can)?
View 2 Replies
Sep 29, 2011
I have procedure (Import) that calls a for a new instance of frmImportData. I also have a class name clsBatch that has a data table property called prpParametersTable.For some reason, I get an error (indicated below with ERROR>>>) when trying to assign prpParameterTable to cv_dtImport2. The error states "Object reference not set to an instance of an object.". Why does this error not happen when I assign dtBP to cv_dtImport1? Both cv_dtImport1 and cv_dtImport2 are equal to Nothing and in my Import procedure dtBP = prpParametersTable.
Public Sub Import(ByVal clsB As clsBatch)
Try
Me.cv_clsB = clsB
[code]....
View 5 Replies
Nov 14, 2009
I have three class files, accounts.vb and transactions.vb in addition to my form.vb. I am unable to retrieve a member variable from on class from inside the other. When the combobox index changes, the program loads the correct account (checking or saving) from two different sequential files. I don't think I have the calcBalance procedure in the correct class file. And that is what I am having trouble with. Accessing it to display it. [Code]
View 1 Replies
Mar 30, 2010
This is a bit of a continuation from a previous post for which AtmaWeapon was very informative.
Problem:
A parent class has a sub class with various properties. A property of the parent class is a List(of T) with T = the sub class The issue is how to store data in the sub class of the instantiated parent
Some example code (hopefully formatted correctly):
Code:
'=========== Class Definitions =============
Public Class courseClass
Public Class timeTableClass
[Code].....
View 7 Replies
Oct 1, 2009
I'm looping all the properties in an object via reflection:
For Each p As PropertyInfo In values.[GetType]().GetProperties()
If p.CanRead Then
'Do stuff
End If
Next
how to determine whether the property in question is a generic List(Of T)? If it is I need to loop the list itself.
I've experimented with GetType and TypeOf but have not managed to get anything working.
To clarify, I want to keep this generic. I do not want to specify the type of T, I need to loop the list items and call the ToString method on each item. T could be one of a number of different types (application specific reference types). Is it possible to do this without specifying types?
(VB.NET 2005 with .Net 2.0)
View 3 Replies
Apr 7, 2012
I have a class that has the following property that is generated by the methods in the constructor.
Public Class clsLoadTables
Private _ds As New DataSet
Public Property ds() As DataSet
Get
[CODE]........................
My problem is that I do not want to inherit this class, but I have other classes that need to access the ds DataSet property. If at all possible I would like to not use inheritance and not load my datatable more than once in the program.
Here is my failed attempt to access the property inside another class that is not inheriting clsLoadTables:
[CODE].........................
How I can access this dataset that I want to load only once in the program from many classes without using class inheritance or a global module?
View 3 Replies
Jul 29, 2010
I know that an interface can contain another interface within it.But;can a class contain another class within it?Can an interface contain another interface within it?
View 9 Replies
Jan 11, 2011
I have a List myList of MyObjects. Is it possible to check if myList contains a particular myObject based on a property of myObject in VB.NET? In C#, you'd something similar to this right:
myList.Exists(myObject => myObject.property1 == 3)
View 2 Replies
Apr 27, 2011
I want to read a number of items from a file and then associate each of those items with a new button at run-time, so that when the user clicks one of the buttons I can display some information about that item.Can I use a LIST to manage these buttons and items? Can I create a new class and have each list item of that class, such as 'btnID', 'btnText', etc... ?
View 2 Replies
Mar 23, 2012
I want to set a property of an object that is an array type. If I was declaring and initialising an array of objects, I'd do this: Dim x() as SomeObject = {obj1, obj2}
I don't seems to be able to do something similar with the property, can you do this, does anyone know the correct syntax? myObj.ArrayProperty = {obj1, obj2}
I get Expression Expected Error on the first {
Infer Off
Explicit On
Strict On
Answer : myObj.ArrayProperty = New objType() {obj1, obj2}
View 2 Replies
Mar 23, 2011
Public Class notifierMain
Public Class Contacts
Inherits List(Of row)
Public Sub New()
[code]....
When I debug this winforms application I get curType = "notifier.notifierMain+Contacts+row" I want to the Validate function to know it is in MyContacts. How do I do this?
View 3 Replies
