In one of the VB classes I have for a moving object there are 2 Constructors in the code as below:What is the difference between these 2 constructors?what does the first & the second constructor do?
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I did not know you could do this. See Article by Dan Mabbutt
'from article - Objects, Parameterized Constructors, Anonymous Types and the With Keyword
'by - Dan Mabbutt
Class someObject
[code].....
In c# you can have
public class Foo
{
public Foo(string name)
{
//do something
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Is there a VB.Net equivalent?
Public Class Car
Private Dim CarName as String
Private Dim CarWeight as String
Private Dim CarColor as String
[code]....
1.) In the book I am reading it says that when the default constructor(i.e. the one with no parameters) is executed all the class level variables get set to default values based on their type automatically by the compiler. For example, all String variables would be set to empty string("") and all Boolean variables would be set to False, etc. If you look at all my constructors you will see that non of them get values passed to them for all my class level variables. So my question is for the class level variables that don't get anything passed to them(ex:CarModel), do they take the same default values as they would if the parameter-less constructor were called?
2.) Following from my question #1, is it good practice to make sure that all the constructors that take parameters make sure they set every class level variable. Should I have written the above code as follows?
Public Class Car
Private Dim CarName as String
Private Dim CarWeight as String
Private Dim CarColor as String
[code]....
I would like to know if you can have multiple constructors in a VB.NET class? Like in java, you can have multiple constructors as long as they have different parameters, is that possible here?
View 1 RepliesComing from more low-level languages like C++, and seeing how transparent .NET memory management is, I've got a concert about a piece a line of code I've written. In C++, every object necessarily (dictated design practices and peculiarities of memory management) needs to have a constructor and a destructor. In .NET, destructors aren't needed as often, and there are different patterns of when they are required and how to use them. My question is this. If I have the following like of code (in VB.NET, but equally applies to C#)
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I tried a search, but no luck. Maybe I was using the wrong words, I don't know.Here's my question...called myControl of type CustomControl. I have a property called SomeProperty that can be set in the Properties window. If I put this control on my form and set the property's value to "a string" normally InitializeComponents would look like this:
<System.Diagnostics.DebuggerStepThrough()> _
Private Sub InitializeComponent()
Me.myControl= New CustomControl
[code].....
im converting my classic vb class into vb.net class and im having some problems with my object.Query function
here is my obj.Query Function
Code:
Public Function Query(ByVal sqlStatement As String, Optional ByRef e As String = "") As SqlDataReader
Try
[Code].....
i've got a class called prob that inherits system.exception however it seems not to have inherited the constructor
Public Class prob
Inherits System.Exception
public sub stuff
[code]....
throw new exception("test") 'works Throw New prob("test") 'doesn't work is it possible to inherit the constructor into my class prob as well?
1)When we use Overload constructors in a class
2)and which one is get execut first.
Public Class remoteobj
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I was able to narrow down a problem to a certain point. I was hoping for an explanation or some light shed upon it. I went to Project/Project1/Application/Startup Forms. I found that when I included a "New" constructor in the form I wanted as startup, the form became unavailable for choosing as a startup form. I do not quite understand this because I noticed from work in another document that the form I want (call it StartupForm) actually has a basic "New" construction with no arguments, so that is why I do not understand quite what is happening here.
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Why I am I getting the "type byte has no constructors" error here?
Dim stream As System.IO.MemoryStream = New MemoryStream()
bitmap.Save(stream, System.Drawing.Imaging.ImageFormat.Jpeg)
Dim image As Byte() = New Byte(stream.Length
i've got a Class like this public Class Cart(Of Item) Public Sub New(ByVal a As Integer, ByVal ParamArray items As Item())but i do not see how to create an instance of it: Dim block_names As New Cart(Of String, 5I)i get something like "type expected" o.O
View 2 RepliesWork = New ExampleWork()Here the Work is a withevents variable and I've used the handles clause for handling various events fired by the ExampleWork object. However the event handler will not get assigned till the constructor of the ExampleWork returns. Now how can I handle any events fired from the constructor? I can move the constructor logic out to a separate method and call it after the constructor has returned and thus handle all the fired events including events fired from constructor. However it doesn't look good
View 2 RepliesI'm fairly new to WebService development and have just set up my own webservice (ASP.Net 3.5, Visual Studio 2008 .asmx file). I cannot find a way of setting up my webservice to take parameters on the constructor. If I create a constructor that takes parameters, it is not then shown when I hook up to the webservice from my application (it only shows a parameterless constructor).
View 2 RepliesI would like to open a new form from some other form, and pass some selected object from a control on that form to the new form. The sensible way to do this, I thought, was as a parameter to the forms constructor. Now I know that the visual studio GUI creates partial classes for my forms, that hold the properties that I can drag onto there in the designer. I assume it also holds a default constructor. Since it might do all sorts of stuff that is needed to initialise the form, I figured I should call it from my custom constructor ala
public sub new(byval my_parameter as Foo)
Me.new()
Me.my_parameter = my_parameter
[code].....
That clearly wasn't it, because it can't find a default constructor. The thing is, visual studio goes trough great lengths to prevent me from seeing the generated constructor, so I know how to access it. This leads me to believe that I am actually doing it wrong, and should have set out on some different path, as the path you are forced in to usually is the sensible thing to do, which I usualy find out way too late.
In my previous application using Linq2SQL I was able to overload constructors with parameters by doing this:
Namespace CoreDb
Partial Public Class Accomplishment
Public Sub New(ByVal accomplishmentTypeID As Object, ByVal description As String, ByVal title As String, ByVal applicableDate As DateTime, ByVal lastUpdatedBy As String)
[code]....
Basically using a partial class off the object, sharing the namespace of the .dbml file and calling the default constructor and then doing additional stuff. So then in my code I could do something like:
Dim accomplishment As New Accomplishment(id, description, title, applicableDate, lastUpdatedBy)
This seems to no longer work in Entity Framework as there is no default constructor to call.Does this no longer work? And if so what is a good alternative to implementing something like this?
I have a class that implements a range of numbers....call it NumericRange(Of T). Internally, NumericRange stores T as a Nullable, T?. I have another class that wraps this class as NumericRange(Of UInt16). Call this class MyNumRange (I'm being simplistic here). So In MyNumRange, I have a few constructors defined:
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What is the difference between a class with protected constructors and a class marked as MustInherit? (I'm programming in VB.Net but it probably equally applies to c#). The reason I ask is because I have an abstract class that I want to convert the constructors to shared/static methods. (To add some constraints). I can't do this because it's not possible to create an instance in the shared function.
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I'm a c# developer and have not enought experience in VB.NET.the scenario:
Namespace Presenters
Public Class BaseFooPresenter
assuming the public default parameterless constructor[code]....
I can create a method SetValues( ... parameters ... ) and call it from the two constructors but does someone knwos a workaround to avoid this error?, why the compiler do not validate the possibility to call the base constructor before the overloaded constructor?how to justify logically the fact that it's not possible to call the base class constructor and another class level constructor from one class level constructor at the same time?
Most of our code base is in VB.NET. I'm developing a project in C# that uses a lot of the assemblies from the VB.NET code.There are three relevant classes in VB.NET:
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Dim regkey As New RegistryKey
i get this error: type microsoft.win32.registrykey has no constructors
I just wanted to try something I had in mind,
Code:
Dim mTreeNodeCollection As TreeNodeCollection
mTreeNodeCollection.Add(New TreeNode("ddsf"))
above produces a 'System.NullReferenceException was unhandled' which is fine.
So I thought dam I forgot to initialise it!!
Code:
Dim mTreeNodeCollection As New TreeNodeCollection
mTreeNodeCollection.Add(New TreeNode("ddsf"))
Now it does not run but i get
Quote:
Type 'Sytem.Windows.Forms.TreeViewCollection' has no constructors
so how the hell I'm I going to get it to work?? can I only Add to a TreeNode collection , a TreeView?
whats the difference between vb9 and c#? and when to use vb9 or c#. i haven't use c# to make a program but i tried to create one application in vs2008 and i found out it is almost the same with vb. how do they differ?
View 2 RepliesI have defined a class with multiple constructors so that the underlying interfaces are immutable once the object is instantiated. I would like one of the constructors to be the "default" constructor for when a user types the following in Visual Studio:
var obj = new MyClass( Dim obj As New MyClass(
Currently when I go to instantiate the object, the constructors aren't listed (in Visual Studio IntelliSense) in the order I declared them in my class. Is there a way to mark up my constructors so that their methods appear in a particular order during instantiation in Visual Studio IntelliSense?
I grabbed an example program to modify for my needs to grab data from a Word doc and transform to XML. Right off the bat I get multiple errors. [Code] I am getting Error Type 'System.Windows.Forms.Application' has no constructors.
View 6 RepliesI'm trying to create a class for storing data on People with another class to store their Bank Transactions.Ideally, this all be hidden away and leave only simple statments, declarations and functions available to the programmer.[code]I know this is possible as these exist in the Listbox Class though can't figure out how it's done.
View 2 RepliesWhat is difference between visual basic 2008 to 2010 please share difference
View 2 RepliesThis works:
CODE:
The only difference is line 14 and 15.
I get different results when i do this calculation in excel and vb.net Value 1 and 2 is a double with 1 significant decimals.and i do this 10* math.Log10( 10^(0.1*value1- 0.1*value2)) and i get different results in excel and vb.net.... is there a difference in Log10 algorithms in Excel and VB.net and/or is the values used in Excel not a double (Singel or decimal perhaps)?
View 8 Replies