Why Does Constructor ORDER Matter
May 5, 2009
Why does constructor ORDER matter in VB.Net? I am building a .Net type library which is meant to wrap an underlying COM library completely so that the consumers of the API can pretend to use a nice .Net library with .Net collections and whatnot instead of a COM library.Currently most of my classes are just 1 to 1 wrappers built using Reflection and CodeDOM. These classes have an internal constructor which takes the underlying COM type as a parameter. The CodeDOM builds this as the first constructor to the class. Using these classes from C# proves to be no problem. All I need is a reference to the .Net library and all works good.The problems appear when I try using these classes from a VB.Net project. If the first constructor has a COM type as an argument, the VB.Net project requires the COM interop assembly as a reference. If the first constructor has no arguments or has only managed types all works good. My class library is written in C#.[code]
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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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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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Apr 23, 2009
I am doing something similar to the calulator in windows. My form has a key_up event that allows the user to type numbers. There is also number buttons they can click. Once a number button is clicked, it gains focus and the key_up no longer works.
I looked at windows caluclator and when you click a button there it does not gain focus and the keyboard keys continue to work. How can I get this behaviour?
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May 25, 2009
How can i get form2 to to load exactly center of form1 or a location within the form when i get form2 to show, no matter the location of form1.[code]...
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Apr 1, 2012
I'm using this code to try and show how strong the password is but the panel is changing to DarkRed no matter what is in the TextBox1.What am I doing wrong?
Wrapped it in PHP tags because I think it makes it easier to read >.>
[Code]...
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Feb 9, 2009
I have a "if This > That then" statement, that doesn't seem to work, as it triggers regardless that "This" is smaller than "that". Does it matter that these variables are marked as strings vs integers?
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Jul 14, 2010
I have a grid view with a nested text box in it. I would like to turn view state off but the fact of the matter is when data is posted, the text boxes inside the gridview aren't available (there are no rows in the gridview on postback)I am using ASP.NET 2.0 so would this fall into control state, not view state?
Sample ASPX code of the gridview:
[Code]...
Control's information is not stored in the View State (for things like selected value and .text etc.)Control state, introduced in ASP.NET version 2.0, is similar to view state but functionally independent of view state. A page developer can disable view state for the page or for an individual control for performance. However, control state cannot be disabled. Control state is designed for storing a control's essential data (such as a pager control's page number) that must be available on postback to enable the control to function even when view state has been disabled.[URL]..
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Jan 22, 2010
I am starting design of a program that needs to run no matter if the user is logged in to the PC or not. So I will be writing it as a VB.Net Service.
As I am not overly familiar with SQL Server Express, is it possible to connect to a local SQL Server Express Instance and access the database from a VB.Net Service while the user is not logged in to the PC?
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Mar 8, 2010
Why isn't this working? The number shown on the label gets stuck at 1 no matter how many times I press the button. [code]
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Nov 1, 2009
I have a combo box bound to a datasource. I need to change one combo box (of many) to order the items in descending order.I'm guessing I could order the collection in the dataset, but that will mean all my combo boxes will be reordered?
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Apr 17, 2010
I have a databound Datagridview. The DGV is bound to a datatable of a strongly typed DataSet created using the wizard. Is there any way to re order the columns before displaying them eg: the Columns are displayed in the DGV in this other Col4, Col6, Col3, Col1,Col5, Col2
But I want to it to show as Col1, Col2, col3, Col4, Col5, Col6?
I realise that the display order followed the Column order in the database table and by extension, the datatable. I have re-arranged the columns in the Database but the Datatable still retains the old order.
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Oct 8, 2011
This might not be so 'VB' as it is 'SQL using VB' I have an application with a built in MS Access DB. I have a table that has a column full of integers, I shoot the DB a SQL "order by 'column name' " string and it returns the table ordered by my column of integers.BUT it returns them like this, and I want them like this
0 6
1 5
2 4
[code]....
How do I get the OrderBY to do a descending list starting with the highest number?
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Aug 18, 2011
I'm working on the exercise page 73 (VB 2010 in 24 hours). It's basically a form with 2 text boxes, 2 text labels and a command button. It's really simple and uses this loop to cycle through the items, and tell me the name of them in a Messagebox
[Code]...
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Dec 7, 2010
i used the following codes:
private mediapath as string = "C:movie.avi"
private form1_loads blah blah blah
[code].....
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Jan 14, 2010
I have to order a table following a logical order but I cannot find the appropriate ORDER BY clause.To simplify I have 2 fields field1 and field2
1 record : field1 contains �2� and field2 contains �1�
2 record : field1 contains �1� and field2 contains �2�
3 record : field1 contains �2� and field2 contains �2�
[code].....
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Mar 1, 2010
if a byte value can go up to 255 and two bytes are used to determine the length of packet payload data, how would I convert the two bytes to create one integer value?
State.buffer[13] = 5 and State.buffer[14] = 67
Dim PacketLengthHigh As Integer = state.buffer(13)
Dim PacketLengthLow As Integer = state.buffer(14)
[code]....
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Jul 22, 2009
When is it run? Does it run for each object to which I apply it, or just once? Can it do anything, or its actions are restricted?
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Apr 1, 2010
A project has a class (CAR Class) with the folloiwng details and the CARADMIN cLASS with the following details: The cardAdmin class has 2 constructor Public Sub New() & Public Sub New(ByVal rec As Rectangle) I dont know how to code the latter constructor..
cAR Class has this method/properties:
Public Class Car
Inherits HVSprite
Private fSoundFile As String
[code].....
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Jun 27, 2009
I have a defualt constructor that has a object of a Database connectivity class:[code]therefore in theory i have to call the defualt constructor of Question from overloaded constructor. [code]How every in realitty is it possible to call the defautl constructor from the overloaded constructor
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Aug 17, 2010
Do not know how to convert Me.Base to C#Imports Microsoft.VisualBasic
Public Class ReplaceHTML
Inherits System.IO.Stream
Private Base As System.IO.Stream
[code].....
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Jan 23, 2009
how to pass value other than from constructor.
In my code....value are usually passed through constructor.
ie everything is declared in constructor and while executing, these values are defined in new object.
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Feb 9, 2010
I am rewriting a C# class in VB. The C# class has a static constructor in it:
static Class()
{
...
}
which, through the Call Stack, I found is called by the main window's InitializeComponent() method.Everywhere I've looked has told me that the corresponding static constructor in VB is just:Shared Sub New()
but this method is never invoked. Am I creating my VB static constructor right? Is it likely something else that has nothing to do with my static constructor?
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Nov 10, 2010
A former co-worker wrote a class in C# that was to be used as an attribute. I'm having to convert his work to VB (yeah, it's pointless and way more work than necessary, but management thinks it's a good idea). Unfortunately I'm having an issue because one of the main properties of the class is an ArrayList which is set with a ParamArray in the constructor. The class looks like this (note I've tried to abstract out the problem, so this is a simplified version of the class only)
<AttributeUsage(AttributeTargets.Field Or AttributeTargets.[Property])> _
Public Class LabelAttribute
Inherits Attribute
Public Sub New()
[CODE]........
In the first one, there is just the single label being added. No Problem. In the second one there are 2 different labels being added. Again, no problem. The third one, however, is a problem because it's assuming that the "Description", which is supposed to be the description is instead being interpreted as another label.
This wasn't a problem in C# because it could be set as follows:
[CODE].................
Of course this doesn't work in VB because optional parameters aren't referred to by name as they are in C#. As a stopgap I've changed the constructor to allow only a single label like this
CODE]..................
But that undermines some of what this class is meant to do. Does anyone know how, or even if I can get the same basic functionality to work in VB?
Think there must be a way to make the existing design work. Imagine this class was built into a library that I could not modify. Would I be forever forbidden from setting Description because of this design?
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Jun 29, 2010
Why VB.NET (vs C#) does not "inherit" the constructors with parameters?
Public Class StopLine
Inherits Microsoft.VisualBasic.PowerPacks.LineShape
Public Sub New()
MyBase.New()
[code]....
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Oct 31, 2011
I've been searching for a while now and can't find a way to add a constructor to the Rectangle Structure.
Is this even possible without inheriting from the class?
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Oct 15, 2010
Im having trouble with assigning a Rectangle to this constructor
fTrainAdmin = New TrainAdmin( )
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Feb 16, 2012
I need to put following code in the Constructor of my startup form.
JohnKenedy.BusinessSQLEXPRInstaller _ins = new JohnKenedy.BusinessSQLEXPRInstaller(" _ <Installation Display Name>", "localhost", "<New database instance name>", _
"<new database name>", "<database password>", "<database backup filename>");
if (_ins.IsDone == false) _ins.ShowDialog();
if (_ins.IsRestart == true) {
Application.Exit();
this.Close();
return;
}
But I really do not know what the Constructor is and how to access it?
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Mar 27, 2009
I know that you cannot specify a constructor in an interface in .Net, but why can we not?
It would be really useful for my current project to be able to specify that an 'engine' must be passed in with the constructor, but as I cant, I have to suffice with an XML comment on the class.
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Mar 9, 2011
I'm not sure if this is possible or not. I have a number of different classes that implement interface IBar, and have constructors that take a couple of values. Rather than create a bunch of almost identical method, is it possible to have a generic method that will create the appropriate constructor?
private function GetFoo(Of T)(byval p1, byval p2) as List(Of IBar)
dim list as new List(Of IBar)
dim foo as T
' a loop here for different values of x
foo = new T(x,p1)
list.Add(foo)
' end of loop
return list
end function
I get:
'New' cannot be used on a type parameter that does not have a 'New' constraint.
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