Override An Abstract Event In Program?
Jun 2, 2009
Ok, I've been searching all over the web for an answer to this and I'm getting nowhere. I've found several examples and tried code translators, but they either fail to compile at all (syntax is wrong) or fail to solve the problem. Here is what I am up against:
I am trying to implement a service object class for the POS for .NET library using VB9. Specifically, the BillDispenser class. I define my class and inherit from Microsoft.PointOfService.BillDispenser. As normal, it creates stubs for all the MustOverride (abstract) properties and methods that I need to override (I love that), EXCEPT for the DirectIOEvent. Apparently this event is defined as abstract in the POSCommon base class, but VB doesn't generate a stub for it.
No compile errors are generated from not defining it, but I get the following runtime error as soon as my unit test attempts to load the dll[code]...
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Jun 2, 2009
I am trying to implement a service object class for the POS for .NET library using VB9. Specifically, the BillDispenser class. I define my class and inherit from Microsoft.PointOfService.BillDispenser. As normal, it creates stubs for all the MustOverride (abstract) properties and methods that I need to override (I love that), EXCEPT for the events. Apparently thare two events defined as abstract (MustOverride) in the POSCommon base class, but VB doesn't generate stubs for them.[code]...
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Nov 26, 2009
I would like to shadow/override an event in VB.NET v2
I need to do it, because I need to implement a interface, let's name it IVisibleChanged, on the custom objects that does not have defined this event, and on the objects that already have defined this event (custom Button, by eg.)[code]...
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Jul 20, 2010
I'm trying to validate a few things in a form I'm building. It has a datagrid with clients info (taken from an access database) and a few textboxes where the user can type some search criteria. The thing is that those same textboxes are used to add new clients to the database and to modify a client's information if one from the datagrid is selected, so I made it that the buttons to insert and modify clients are disabled on load and thenevery time the text on a textbox changes ("TextChanged" event) they become enabled. So far so good. But then I wanted to make it so when a client from the datagrid is selected both buttons become disabled again until the text on a textbox changes (to make sure they're adding a different client and not the same one that was
selected).
I tried using the CellClick event from the datagrid to disable the buttons, but since every time a client is selected from the datagrid the info is shown on the textboxes, this triggers the TextChanged event too, and the buttons become available.So, is there a way I can tell the TextChanged event not to be triggered when the CellClick event occurs?
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Jul 6, 2010
Basically, I have a custom child form class which has events that will be passed to the parent. In the custom child form, I have a declaration of a "MustInherit" class that inherits the DevExpress User Control Class.
The reason for this, is I have many user controls that derive from this base class, and the child form can have an instance of any one of these controls, and doesnt care which. The only requirement is that the child form can handle the same events from each type of control the same way.
Some watered down code snippets(still pretty long unfortunately):
'''Inherited Class
Public Class ChildControlInheritedClass
[Code].....
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Mar 24, 2010
I have a WinForms application (OwnerForm) with some UserControl. When textbox of UserControl is changed, I want to filter content of a OwnerForm. But how can I make it? I don't want to specify OwnerForm inside the user control. I know a solution to add manually handlers for MyUserControl.tb.TextChanged to some functions on a owner form, but I think it's bad way. I'll prefer to have overridable functions, but I can't imagine how to do it.
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Nov 25, 2009
I would like to shadow/override an event in VB.NET. I do it only because I have to implement in this object an interface, that contains the same event like the base object itself, and I need to keep this base event as is it without modification nor supplementary event additions.How can I do it?
Public Shadows Event VisibleChanged As EventHandler Implements IVisibleChanged
So, I would like to implement a interface that contains VisibleChanged event, but to keep functional the myBase VisibleChanged event too.
[code].....
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Jun 1, 2011
I have this code that's suppose to override the form closing event, It fires off sucessfully however doesn't prevent the form from closing.
Private Sub Form_Close(ByVal sender As Object, ByVal e As System.ComponentModel.CancelEventArgs) Handles MyBase.Closing
Me.Hide()
e.Cancel = True
End Sub
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Nov 10, 2009
short question: What's better?
Form KeyDown event vb Private Sub MainForm_KeyDown(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles Me.KeyDown End Sub
Override OnKeyDown
vb Protected Overrides Sub OnKeyDown(ByVal e As System.Windows.Forms.KeyEventArgs) MyBase.OnKeyDown(e) End Sub
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Jul 19, 2009
I'm using ASP.Net 2.0. I have a custom control that is inherits from a 3rd-party vendor's control. I'm trying to override the Render method. [code] What I need is that under certain situations I want to be able to render a Button instead of the original control.But I want the Button to have the same client Id as the control so that I can use javascript to manipulate it.How do I assign a clientid to the button?
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Nov 9, 2011
When editing vb.net forms code in vs2008, how do I select base class events that I want to override? In vs2003 there was a list of overridables in the drop down list but now that list is missing?
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Sep 8, 2009
I have to two forms. Form one has several check boxes and when a button is pressed, a second form is opened and certain functions are ran based on which check boxes are selected.The problem is that the second form doesn't show until all of the functions are done.I decided to use the Form's Activated event, which works fine. However, the event fires every time the form comes into focus.Is there anyway to override the event and make it only fire once?
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Feb 2, 2010
Basically, what I want to do is create a new control called EncryptedPictureBox. The image path I would be loading into ImageLocation would be the path of a 512 bit encrypted image. Normally if I load this type of file, it will not display. So I want to override Load() so that I can write the encrypted image to a stream, decrypt it, and then display the stream. I'm trying to save processing time so I don't have to grab the encrypted image, save it to disk as a decrypted image, then display it, then when done, delete the decrypted image from disk.
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Mar 26, 2011
Correct me if i'm wrong, but i believe most (if not all) classes in the CLR that raise events raise those events from protected methods, for example Form.OnMouseDown... so... In a subclass, when would you want to override the "OnXyzMethod" instead of simple adding an event handler like Visual Studio does by default when you want to handle a controls event?
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May 20, 2011
At the moment I have the following Command class:
Public Class SubscribeCommand
Implements ICommand
Private ReadOnly _vm As MainWindowViewModel
Public Sub New(ByVal vm As MainWindowViewModel)
_vm = vm
End Sub
[Code]...
In a tutorial i read, you have to implement add {} and remove {} for the canExecuteChanged-Event. But how can i do that, with vb.net?
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Apr 13, 2012
I want to modify this code or replace it. I want to override the the textbox's textchanged event in a user control.
Protected Overrides Sub OnTextChanged(ByVal e As System.Windows.Forms.ItemChangedEventArgs)
MyBase.OnTextChanged(e)
End Sub
[code]......
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Nov 7, 2009
I would like to somehow override the "GotFocus" and "LosFocus" event of the textbox.
Here's the deal. I have big registration form with +- 200 TextBoxes and I want the one that has focus to be highlighter [e.g. let's say change the background color to yellow]. I know, I could write the same code for 200 TextBoxes, but that would be time-killing and I'm really not in favour writing the same thing 200 times as well as with such a huge amount of copy-paste I'm almost sure I would make mistake somewhere.
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Jan 6, 2010
I created a vb.net dll which I am using in an unmanaged c++ project.When I try to create an object of the class, I am getting an error:cannot instantiate abstract class.Why would my class be abstract? How can I modify it so that it won't be abstract?
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Sep 29, 2009
I am doing a project on abstract the numbers that i get from the datagridview to append it on the other textbox. Ok I elaborate more. I have 2 form which is form1 and form2. For the form1, the view is 2 textbox and a 'To' button. when click on the 'To' button, it is direct to form2 which is the datagridview. After selecting the selected numbers, it will display the numbers on the form1 of the one of the textbox. but the problem is I want to abstract one by one of the numbers and append it on the other textbox of the form1.
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Sep 29, 2009
I am doing a project on abstract the numbers that i get from the datagridview to append it on the other textbox. Ok I elaborate more. I have 2 form which is form1 and form2. For the form1, the view is 2 textbox and a 'To' button. when click on the 'To' button, it is direct to form2 which is the datagridview. After selecting the selected numbers, it will display the numbers on the form1 of the one of the textbox. but the problem is I want to abstract one by one of the numbers and append it on the other textbox of the form1.
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May 3, 2011
I'm trying to use the builtin XML literals feature to create/read xml files using my own schemas, but I don't see a way to cast an abstract XElement from a base type to a more derived type.The schema/xml below shows in general what I'm working with, but using XML literals only allows me to use the base type in the IDE, so the xml below is treated as a collection of elements of the base type, instead one of the base type and one of the derived type.
<schema targetNamespace="Test" xmlns="Test">
<xs:complexType name="Base" abstract="true">
<xs:attribute name="Id" type="xs:int">
[code]....
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Mar 30, 2011
I have one interface that contains four functions. I have about 20 classes that implement this interface. Throughout each class, I see a lot of duplicate code, for example, there are constants declared at the beginning that are in every class. The method implementations (logic) of the interface are mostly the same.It contains duplicate structures. Is this a case where I can eliminate a lot of duplicate classes by implementing an abstract class instead of an interface. What I am striving for is too be able to put common methods from the abstract class as non-abstract methods and then methods that need their own implementation would be marked over-ridable. Can I put consts and structures in abstract classes? If so, that would eliminate a lot of duplicate code across the classes. Is there anything else I should look out for in the classes as a sign that I probably should be use an abstract class instead of an interface.
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Sep 8, 2011
I'd like to make sure each of the subclasses has a certain nested class whose actual fields are up to the developer.
Nesting an abstract class inside the base abs. class doesn't seem to do the trick because during actual coding, both the nested abs. class and the nested class in the subclass both are available (show up in intellisense).
Having the base class implement an interface that includes a class doesn't work since interfaces only refer to methods that can be implemented, not classes (meaning implementing the interface requires implements methods, but says nothing about classes in the interface.
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Jan 31, 2011
understanding difference between an interface and an abstract class which has no function with implementation?which is better abstract cls or interface in term of speed, features..?
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Feb 1, 2012
My immediate issue is that currently I have a 3 tier solution (Presentation.aspx.vb calls BusinessLayer.vb which calls DataAccessLayer.vb). However, I want to make BusinessLayer and DataAccessLayer.vb abstract classes because several Webforms will use have the same functionality.
So I currently am doing this (no abstract classes):
'Presentation Layer (pseudocode)
public sub checkUser(byval userName as string, byval dept as string)
dim isGood as boolean = BL.checkUserAccess(userName, dept)
[Code].....
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May 13, 2010
I am developing a web app but is not satisfied with is architecture that I am following. The architecture is plain old conventional 3 tier architecture. What i want is follow some design pattern or architecture that will be help me in decoupling my code.I have idea about MVC and MVP architectures for Web App but i need different from that. I want to use OOPS concepts using abstract classes and interfaces, polymorphism etc in my app but not MVC and MVP. I dont know why?
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Mar 4, 2011
explain to me the differences between an abstract class and a class marked MustInherit?
Both can implement shared and instance constructors and logic. Both can/must be inherited.
So why use one over the other and what is the difference?
Edit: Sincerely apologize I have got my languages mixed up. Will mark correct answer as soon as I am allowed.
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Jan 12, 2011
Let's have three classes;
Line
PoliLine
SuperPoliLine
[code]...
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Jan 19, 2012
I've been playing around with implementing an abstract base class that using reflection accomplishes SQL to Object mapping.
I did some benchmarks and decided I wanted to implement a caching strategy for the property info of the objects (to prevent future lookups on them). My first instinct was to try and implement something like this.
Public MustInherit Class BaseModel
Implements IFillable
Private Shared PropertyCache As List(Of PropertyInfo)
[Code]....
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Mar 31, 2010
I am trying to compile the following code and i am getting the error[code]...
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