Setting Property Of Class (LifeLine)
May 1, 2010
I'm new to classes. In my Who wants to be a Millionaire application, I have a Lifeline class and I create three instances of it - FF, PAF and ATA (50/50, Phone a Friend and Ask the Audience). Something I do with a lifeline is put a cross over its logo, hence the need for a centrepoint property, which marks the centre of the cross on a form.
Public Class Lifeline
Private ptCentrePoint As Point
Public Property CentrePoint() As Point
Get
CentrePoint = ptCentrePoint
[Code] .....
What happens is that at the "Call Form2.DrawCross(Form2.CentrePoint)" line, the tooltip shows that the FF object's centrepoint property isn't set (as I thought it would be by " FF.CentrePoint = tmpPoint").
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Sep 16, 2009
Given a simple class like this:
Public Class clsOB
Implements System.ComponentModel.INotifyPropertyChanged
Private _Frequency As Double
Private _Value As Double
Public Event PropertyChanged(ByVal sender As Object, ByVal e As
[Code] .....
And then I'd like to do something like this:
Dim
o As
New
clsOB(50, 30)
o = 31
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Apr 12, 2011
In on a section of my book about classes and properties. In this example, the author is attempting to show how you can validate a value passed to the property before setting the property. Looks like so far in this book, a couple of things have slipped past the editor, and I think this might be another one...Here's the example:
[Code]...
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Feb 5, 2011
E.g. I have a class:
Namespace Common
Public Class AClass
Public Class BClass
[code]....
How can I use BClass without saying AClass.BClass, I've see some existing code using this format, but I can't find the setting.
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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.
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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'?
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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)?
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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]....
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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]
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May 31, 2011
I have the following property in a class:
[Code]....
The problem is that when I try to set the property like this: myClass.Language = "English" The property is set to "English" and not to "<![CDATA[English]]>" which is what I want. What is the reason for that and how can I fix it? When placing a break point on End Set and use the Watch window to inspect the value of _Language after setting the property to "English" it remains "English" and doesn't change.
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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].....
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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.
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Nov 8, 2010
I am converting a 1.1 .NET web app to 3.5, and I've run into a bit of a jam.
One web control has a Property that sets the page title label on that web control.
End Property
When a page with the web control was loaded before, it would set the Property to a given string, like in ucHeader.PageTitle = "This is a string." Now, if I don't remove the lblPageTitle.Text = Value, I get a NullReference Exception.
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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?
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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?
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Aug 10, 2011
I have this simple code,
Protected Sub grdSearch_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles grdSearch.SelectedIndexChanged
TimeOff.Where = "UserName=""" & grdSearch.SelectedValue & """"
End Sub
Doing so causes this error, 'UserName' could not be resolved in the current scope or context. Make sure that all referenced variables are in scope, that required schemas are loaded, and that namespaces are referenced correctly. Near simple identifier, line 6, column 1.
The datasource works fine before the where property is set.Update: I found the issue but I still don't get it.Adding it. in the where clause solves the issue. Like this,
TimeOff.Where = "it.UserName=""" & grdSearch.SelectedValue & """"
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Feb 20, 2012
I am using a user control using vb.net. It include the program to retrieve the values from database while giving the paramers. When I set the property from my main program i am getting an error "Invalid attempt to call Read when reader is closed." When i gone to the online help i got the message as follows "System.InvalidOperationException (.NET Framework 4)The exception that is thrown when a method call is invalid for the object's current state. InvalidOperationException is used in cases when the failure to invoke a method is caused by reasons other than invalid arguments. For example, InvalidOperationException is thrown by IEnumerator.MoveNext if objects of a collection are modified after the enumerator is created, or ResourceSet.GetString if the resource set is closed before the method call is made. If the method invocation failure is due to invalid arguments, then ArgumentException or one of its derived classes, ArgumentNullException or ArgumentOutOfRangeException, should be thrown instead.[code]
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Nov 12, 2009
I am programatically creating instance of usercontrol as shown below
[code]...
I have two public properties in my usercontorl like clerkName and RespName. How can I set those values in the above code. Intellisense is not showing ClerkName and respName Properties.
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Feb 3, 2009
i want to set autocomplete textbox, but if multiline property of textbox is true, i can't do it.
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Nov 9, 2011
I'm reading in a configuration file which is simply a txt file that configures my Com port and sets some directories. It's basically for the end user to set the interface. I want to give the user the ability to change backcolor properties on my NumbericUpDown property. So when I read in the Config.txt file the end user can change coloring on the General Form. In this case the NumbericUpDown. How to assign a variable for color from my string (from my txt file) that I read in.
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Aug 4, 2011
Im currently debugging my application to found out why it's running a bit slow, when I put breakpoint where i populate one of the application combobox it's run fast but after i populate it and when I'm trying to set the its selectedindex to zero the program halt for about 2 second.. this is the line where the program get stuck for 2 seconds:
[code]...
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Aug 24, 2010
I am creating a customised version of the ListView control and there are several of the properties that a ListView has that I would like to be set to a different value to the ListView default when a user goes to use my user control.
From what I've found there seems to be a number of people suggesting just set them in the constructor, but to the best of my knowledge that would just mean that the user would not be able to change the properties in the PropertyGrid in the VS IDE.I assume this is probably something extremely simple that I have overlooked.
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Feb 9, 2010
I have a single form that I would like to move across the screen with my VB program. Of course it's simple to set the location X and Y property for compile time using the properties tab, but I want the form to move as the program runschanging the coordinates within a for-next loop.I can easily get the X and Y coordinates of the form within my program by using X = me.location where X has been dimmed as type point.console.writeline(X) will appear as {X=20, Y=40}. for example
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Oct 6, 2010
.From = New MailAddress("Me@MySite.com", "Big Mike")This does not;
Dim AddressFrom As String = "Me@MySite.com"
Dim FromDisplayName As String = "Big Mike"
.From = New MailAddress(AddressFrom , FromDisplayName)
I receive the error; The specified string is not in the form required for an e-mail address.I would REALLY like to use variables here so that I can read these two pieces of data from My.Settings. I've been searching for the answer for hours and I'm stumped.
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Sep 17, 2011
Can someone clarify if there is ever a need for the below?
When setting a textbox "Visible" property to False is there any reason why I should also set the "Enabled" property to false.
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Mar 31, 2009
I have a lambda function that I can assign to a field and pass it to a sub routine, but cannot assign to a property. My field is defined as follows:
Public Delegate Sub SubDelegate()
Private pDeleteFunction As Func(Of BookCaseRow, SubDelegate)
[code].....
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Aug 12, 2009
Trying to set a Combo Box RowSource to a field in a table that contains the choices separated by semi colons. Have tried both a query and a DLookup but it results in displaying the full contents of the table field, e.g. "10;12;14;16" rather than giving me the usual selection list
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Feb 25, 2011
VS 2008, vb.net, Win7 development machine. I've developed a Windows application with several different forms, and am using the My.Settings feature. This is the first time that I have used this feature. For each form, I have set the form's property binding 'location' property to an entry in 'settings' of My Project settings page of the VS 2008 development environment. The settings are set to user scope.
1.) Do I need to add any code to my application to make the settings work, or is it sufficient that I have the "Save My.Settings on shutdown" set to true?
2.) When I create my setup to install the application, what settings file (app.config?) do I install to the user's machine, and what folder should it be installed to?
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Nov 15, 2010
I am using VB 2008...
On my form I have a "Combobox1" that pulls a list from an access table. I also have a "DataGridView1" that pulls data from another access table.
I am trying to set the "DataSource" property of the "DataGridView1" after clicking a button, which pulls the "Text" property from the "ComboBox1".
ComboBox1.Text will always equal DataGridView1.DataSource as a text string.
I researched the Get/Set command, but it does not make sense to my specific application. I have read countless articles online for weeks, but I have now taken the next step.
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Jan 3, 2010
When I drag a dataset onto a form (as details), is there a way in which the textFields maxLength property is automatically set with the width within the actual table. Or do i have to select each textBox and enter it manually?
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