Default Value At Declaration Or In Constructor?
Mar 4, 2011
One would think I'd already know this, but I never really gave it much thought before now. When declaring a member variable for a class, is it better to set the default value at the declaration
Private m_strMyVariable As String = ""
Or is it better to do it in the constructor
Private m_strMyVariable As String
[Code]....
Should I maybe always specify a value at declaration, even if it's Nothing, and just override that value in the constructor(s) as needed? Or is it situation specific? If so, a really quick rundown of which situations might warrant which treatment would be nice.
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May 25, 2011
I have been getting up to speed with the MVVM pattern in Silverlight and was wondering how to implement binding from the View to the ViewModel when the ViewModel constructor has a parameter if an interface type.If I bind the viewmodel to the view in XAML then you can not use a parameterised constructor. Given that I was creating a default constructor passing an instance to the parameterised constructor but this breaks the abstraction.
View
<navigation:Page x:Class="QSmart.DataViewer.Report.RecentFailures.Report"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
[code]....
Is it recommended to use the code behind of the view to pass into the parameterised constructor and then bind to the viewmodel?
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Jan 19, 2011
I have written a number of classes in my time in VB.NET which set the basic elements in a custom New constructor through parameters. This makes things easier and enforces discipline. However, using Public Sub New() becomes pointless. If someone else tried to use this class, he or she could make a mess of it all by using Sub New without the arguments. I'd like to remove this method but I haven't found out how. I could make it raise an exception, but that somehow seems unseemly. I'd like a neater way. Does anyone know how?
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Feb 3, 2010
I'm doing a lab for school, and I came across something I have never done before: create a default constructor within my class. It involves creating a private field to store the connection string, then create a default constructor that sets the connection string.
Here is what I have so far:
Public Class Appointments
Private sqlconnection As String = ConfigurationSettings.AppSettings("ConnectionString")
Private Property connectionstring() As String
Get
Return sqlconnection
[Code] .....
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Dec 27, 2010
I have a base class which must be overriden. This base class sits in one dll shared by all. The derived classes will each be in their own dll such that the addition of a new derived class can be done by distributing a new dll. The set of dlls, and therefore the set of derived classes, will be discovered by the main program on startup. That's all pretty straightforward. The problem is that the main program needs to be able to query a database to figure out which type of derived class it needs, then create a class of that type. Naturally, it can't know which types will be available ahead of time because even I don't know that. The program has to be dynamically extensible.The obvious way to do this is to have an interface in the dll that is implemented by a class with a default constructor. The sole purpose of that class would be to return an object of the type (one of the derived types) defined in that dll. The derived types can't really be this class, because they can't have a default constructor since the base class doesn't have a default constructor, and the derived class can't make up the arguments that the base class constructor needs.
So basically, each dll that houses a derived class would also house a simple class that implemented an interface for the sole purpose of creating that particular derived class. The main program would examine the dll to find a class that implemented the interface, and once it found one, it could ask it what type of class it created, or it could ask it to create an instance of that class. It seems like there ought to be an easier way to dynamically add new classes to the project. It seems like the derived class ought to be able to tell the main project what type it was. This could be done, except that the derived class would have to exist before any of its methods could be called unless the methods were shared. Since you can't have a shared method in an interface, the interface itself would make no sense at that point, in which case I would need to discover whether the class in the dll derived from the base class in the second dll, just to figure out whether or not I wanted to create it. That's getting convoluted by now, so I guess I'll leave it there. The basic point is that the base class is known to the main program from a common dll. The number and types of derived classes can't be known at this time, so the program has to be able to discover them dynamically. Each derived class will sit in its own dll (or there could be more than one in a dll), and has to be discovered, and instances created, as needed, by the main program.
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Jan 1, 2011
where can I find the default constructor of a windows form? I mean:
Public Sub New()
End Sub
I should say that I Use Visual Studio 2008 as my editor.
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Apr 21, 2010
Why are static variables set equal to 0 in the declaration when 0 would be the default value of the numeric variable anyway when it's first declared? Not including the "=0" in the static declaration seems to work with no problem.
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Mar 16, 2012
I'm trying to create a Wizard at runtime in VB.NET using the WPF NavigationService and I'm having some problems. I need to add controls to the PageFunction pages at runtime which seems to involve passing arguments to the PageFunction pages when I create them (prior to navigating to them). This means that the PageFunction pages need to override the default constructor and add arguments to it. This seems to work fine.
The problem is that I also need to call OnReturn once I've navigated beyond the first page (to go back to a previous page) but the OnReturn doesn't work unless I use the default constructor on the PageFunction page it is navigating back to. The work around I've been considering is creating some global values that the PageFunctions could acssess at runtime in their default constructor but I can't figure out how to define global variables in the MainWindow that the PageFunction pages can get access to.
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Feb 15, 2010
I have an abstract class which requires a delegate to function. I pass the delegate into the constructor. Now that I have a non default constructor I need to call the abstract class's constructors from the concrete class which means that I need to use MyBase.New(...). I have included a quick example below.
Public MustInherit Class BaseClass
Public Delegate Sub WorkMethod()
Private _Work As WorkMethod
[code]....
I have tried to do this but I keep getting the following error: "Implicit reference to object under construction is not valid when calling another constructor".Can I not do what I am trying to do above? I initially had the delegate setup in its own setter method. But then I am creating a deceptive API because it does require a point to a method to work properly.
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Jun 21, 2011
I got problem regarding declaration of dynamic runtime array declaration Here is my code
[Code]...
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Nov 2, 2009
what's the rationale behind this limitation: Constructor call is valid only as the first statement in an instance constructor i want to pass an argument to my constructor which validates this argument and calls mybase.new according to this argument but it doesn't let me
example:
Public Class prob
Inherits System.ApplicationException
Public Sub New(ByVal problem As String, ByRef inner_exception As Exception)
[code]....
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Dec 3, 2011
I need to print the contents of 3 textboxs to default printer. what examples I have found dont seem to work. I was trying the documentprint1 component as i thought it would be easy but cant figure out how to tell it what to print the second part is to print a variable (string) to the printer as well.no need for user to select just straight to default printer with its default settings
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Nov 25, 2011
I have a combobox which contains a sample of names selected from a table.Currently the default name displayed in the box is the 1st name found in the table. What I would like to do is display the name of the person who is doing the selection as the default. The name is stored in a public variable 'PubName' and I do not want the user to be able to type into the combobox themselves.Is this possible?
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Jun 9, 2012
I am creating my own browser. I want to make an option...to set as the browser to default.To do that I have to:Write a code which opens html(generally internet) file through my browser(form load event) DoneChange the "open with..." of the .html,.xml.... files Problem I want to change the open with event from my web browser. Actually i want an options form which will ask the user "Do you want to set /Browser name/ to be your default browser?" If yes then it will change the default options of the internet files.
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Feb 26, 2009
How can rightfully declare these in VB.net , in my coding it's highligted errors on these declaration.
Dim excel As New Microsoft.Office.Interop.Excel.ApplicationClass
Dim wBook As Microsoft.Office.Interop.Excel.Workbook
Dim wSheet As Microsoft.Office.Interop.Excel.Worksheet
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Jan 19, 2011
I am currently working on VB. I am using Visual Studio 2008.
The piece of code below is a console application which builds without any error.
Imports System.Net
Module Module1
Public Sub Main()
[Code]....
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Aug 6, 2009
I was told to use this to specify a folder that I want my node to go to.
(Declaration)
<ComVisibleAttribute(True)>
Public Enumeration SpecialFolder
(Usage)
Dim instance As Environment.SpecialFolder
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Mar 8, 2010
In this
Dim [end] As Point = e.Location
what is the significance of the [] 's?
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Dec 16, 2009
What is the appropriate declaration such as "ValueChanged" or "Click" for a NumericUpDown that will execute the code when I press enter. I already know that setting the "AcceptButton" property of the main form to a default button will not work, especially if I want a different button to be selected depending on which control I give focus.
PS: Is the syntax any different from Visual Basic 2010 Express than it is on Visual Studio 2012 RC (running in Visual Basic Mode)?
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Apr 22, 2010
This is some homework material[code]...
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Sep 15, 2010
Question: How to shorten this array creation ? I need to create an array of type ReportingService2005_WebService.Property with one property.
Something like:
Dim PropertyArray() as new ReportingService2005_WebService.Property(1)
I have to do this:
Dim PropertyArray As ReportingService2005_WebService.Property() = New ReportingService2005_WebService.Property(0) {}
PropertyArray(0) = New ReportingService2005_WebService.Property
[Code].....
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Jan 5, 2009
For some reason when i declare an array and set it to a certain amount of elements then under it specify the elements it works in VB 2005 but when i do it in VB 2008 it get : "declaration expected " and i get words underlined.
Public Class Form1
Dim words(20) As String
words(1)="Computer"
End Class
Let me know how to do this in 2008!
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Aug 30, 2011
Currency Declaration in vb2008.
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Jan 16, 2012
There's error in the codes below: but I can't see what caused the error
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Jun 30, 2010
A "declaration expected" error occurs when attempting to use any of the MY objects. What declaration needs to be made?
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Jul 6, 2010
Does anyone know of a working declaration for the API "AccessibleObjectFromEvent"? Or a good .net equivalent? I've spent so much time getting the other main Accessible API to work on .NET, that I'm hoping to start with a good declare on this one.
I've built a really good narrator, for totally blind people so that they can interface and use the computer in a substantial way. The innovation is a static mouse that controls category input, rather than free mouse movement, and the middle wheel selects items of that category. But I need the last access API for events and voice feedback when the event occurs. I'm guessing it's something like this, according to what works for the other API: Code:
This is loosely based upon microsoft Access example written in vb6, available as an online download. I've have not seen a .NET example online, so it might prove useful for someone.
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Apr 15, 2011
how to solve the error message " ConfigurationaManager not declared" when used to connect to database here is the line of code which gives the error
SQLConnStr= ConfigurationManager.ConnectionStrings("SQLConnStr").ConnectionString
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Jun 7, 2012
I am creating a kind of a "naive" search engine.What I have done is distributed words in files where each file corresponds to the starting letter of the words (i.e. if its English, then 26 files are there)Then when the search system loads I am loading all the words in hash tables (26 hash tables corresponding to 26 alpha-characters) for which I am using an array of structures.The problem is after declaring the variables in a Form load subroutine, the variables are not able to use those values in other subroutines..How do I properly declare them so their values persist?
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Aug 23, 2010
I need to Dim lblFilePath. As what do I Dim it, String dos not work. This might not makes sence to you,
[Code]....
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Dec 15, 2009
Declaring Varibales where to put the declaration.
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