Implementing Events In A Base Class?
Nov 15, 2010
Consider the following objects:
Public MustInherit Class FileRepository
Public MustOverride Sub SaveStringToFile(ByVal FileText As String, ByVal FilePath As String)
Public Event FileSaved(ByRef sender As Object, ByVal EventArgs As EventArgs)
[code]....
I want my base class to raise the FileSaved event in it's implentation of SaveStringToFile once it's saved the file. However in VB.NET you can't have a derived class raise a base classes event. I suppose I can treat XMLFileRepository_FileSaved as a standard function call and have my SaveStringToFile implementation call it directly?
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Nov 8, 2009
suppose I have the following hirarchy:
Public Class PrimalClass
Public Event SomeEvent()
End Class
Public Class BaseClass
[code]....
this code compiles and runs.what I want to do, is remove the event SomeEvent in BaseClass so that DerivedClass won't be able to register a handler to it.
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Feb 18, 2011
When i use my UserControl in a project my Mouse Enter & Leave events aren't firing, i assume i fix this with a raiseevents in my usercontrol. However when i try to do this it says something about "cannot raise base event from derived class".
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Jul 4, 2011
Something that has been confusing me for a while now with WPF MVVM is for example, when I have a base model containing nothing but a few properties and some validation code and I then build a view model around this base model, how should the view model be structured.
For Example:
Base Model ->
Imports ModellingHelper
Imports FTNHelper
[Code]....
What I am wondering is, if there is a better way to structure the view model to improve data binding, so I don't have to bind to Source.Name etc. How should I handle the base model in the view model?
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Mar 12, 2010
When I do this
Public Class cInherits : Inherits Panel
I get this: Base class 'System.Windows.Forms.Panel' specified for class 'MenuButton' cannot be different from the base class 'System.Windows.Forms.UserControl' of one of its other partial types.
How do I inherit?
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Apr 15, 2010
I have put this code in the global form Inherits System.Windows.Forms.Form. And then in the form that will inherit this from the global Inherits MenuStrip. "MenuStrip" is what the global form is called. But keep getting this error: Error1Base class 'MenuStrip' specified for class 'Lesson2' cannot be different from the base class 'System.Windows.Forms.Form' of one of its other partial types.
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May 19, 2009
i have a base class which declares the event StatusTextChanged. My child class, of course cannot directly raise this event.
[Code]...
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Oct 1, 2008
I've been creating short test apps repeatedly to try to understand some of the concepts in VB.NET.For the most part it has been illuminating.I read Bucky's .NET knowlegebase tutorial on passing objects as parameters to newly created forms. He shows how to create a new class that inherits from the base form class and define a New() method with parameters Extending the concept I thought about doing the same thing with a form that was created at design-time (In this case Form2).
[Code]...
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Apr 22, 2012
Base class has one field to hold numeric balance value. With 2 methods that accept arguments for adding and subtracting the new input calculating new balance. Sub class has four fields dates, transaction, memo and amount.I have a deposit form, and withdraw form. Each time one transaction is entered it creates an object with sub class fields, then adds to the account collection. My problem is not understanding how to call the deposit/withdraw method and pass the current transaction amount back to the base class to alculate the new balance. Does anyone have any links to information/tutorials on how to perform something like this? As you can see with my code I have tried various different approaches without any success.
[Code]...
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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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Apr 9, 2010
I am trying to create a class in VB.NET which inherits a base abstract class and also implements an interface. The interface declares a string property called Description. The base class contains a string property called Description. The main class inherits the base class and implements the interface. The existence of the Description property in the base class fulfills the interface requirements. This works fine in C# but causes issues in VB.NET.
[Code]...
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Dec 29, 2010
This is another one of my "I think it's not possible but I need confirmation" questions.I have a base class for a bunch of child classes. Right now, this base class has a few common properties the children use, like Name. The base is an abstract class (MustInherit)Technically, this means that everytime a child class is instantiated, it lugs around, in memory, its own copy of Name. The thing is, Name is going to be a fixed value for all instances of a given child. I.e., Child1.Name will return "child_object1", and Child2.Name will return "child_object2".
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Jun 10, 2011
Suppose I have piece of code like this:
Public Interface ISomething
....
End Interface
[code]....
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Sep 25, 2009
I suspect I am being very silly here but I have the following setup
Class MustInherit myBaseClass
'some stuff
End Class
Class myInheritedClassA
[code]....
Running this results in the following error
Unhandled Exception: System.InvalidOperationException:
There was an error generating the XML document. --->
System.InvalidOperationException:
[code]....
is there any way of 'Widening' the inherited class to the base class so this would work?
EDIT:regarding XmlInclude(typeof inheritedClass), currently this method could potentially return a number of types of inherited class (i.e myInheritedClassA and myInheritedClassB) is it case of simply having to add each of the inheritedTypes in this tag?
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Oct 28, 2010
I am working on a plugin architecture and after some reading I have settled on one. The host class will be implemented in C# as well as some of the plugins for that host. The issue I am having is that some of my team uses VB.net. So the question, is it possible to implement a C# (plugin)interface in VB, such that when it is dynamically loaded into the host program it will have the methods required by the interface.
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Oct 22, 2010
How do I access the base class inside a derived class?
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Dec 10, 2010
If we are within the derived class then ofcource we can use MyBase keyword to access base class's object reference . That's fine , how can we take that base class's object reference outside that derived class's definition.My following code will explain what i want . Actually that is giving error right now, but it is explaining my requirement .
Public Class Base
Public x As String
End Class
[code]....
Actually there is error in ReadOnly Property BaseReference's Getter . Error is "Error 1 'MyBase' must be followed by '.' and an identifier. " how can i get base class object reference in Main method ?
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Apr 3, 2009
I am migrating my code from vb.net 1.1 framework to vb.net 3.5In my windows application, the base window has some buttons and events are written for the same.I have shortcuts defined for these buttons also, for example: ctrl+d, DEL (keyboard) etc.Now i open a property Grid form on top of my base window for a selected object.Even when the focus is on this property grid, i am noticing that my base window events are firing on pressing those shortcuts.
example:I select some text in my property grid and hit delete button from keyboard. The delete event that i have written for the selected object gets fired and the text is not deleting.I fail to understand why is it happening. It wasnt behaving like this in .net 1.1.In .net 1.1 it would delete the text and only when the focus is back on the base window, hitting Delete would call the event.How do i control such a behavior? Is there some property that i need to set for property grid in .net 3.5 to prevent base window events from firing till the time focus is on property grid form?
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May 30, 2009
Usually, if I make a class that has an implementation and also inherits a class with same method signatures, then I do not need to manually add implementation code. For example, if I create a class that inherits List(of Double) and Implements IList(of Double), then I do not need to add any code to make this compile, since the program realizes that the inheritance covers all the methods of the implementation. (Even though VB will auto-generate methods you can remove them no problem).
Now I'm trying do to something more complicated, using an implementation on top of IList, with a class that has a chain of inheritances, and the program won't accept it. See this example:
Interface ICustomList
Inherits IList(Of Double)
Sub TestSub()
End Interface
Class BaseList
[Code] .....
The final item, CustomList, is not compiling. The program says 'TestSub' must be implemented, but by inheriting BaseList, the class has a TestSub (and it is recognized by intellisense)! All the subs exist, they are functional, so why is the implementation not valid? (I know I can get rid of this error by manually creating an (overloading) TestSub in CustomList and specifying that it is an implementation. However, this should not be necessary since it already exists, and if I am going to be building a chain of classes inheriting each other, this could potentially become time-consuming and annoying.)
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Jun 17, 2012
I am trying to create a class implementing the generic IComparer of my own class "Stellungen" (which translates to positions, like on a chess or checkers board).
This is what I got:
Private Class comparer(Of Stellung)
Implements System.Collections.Generic.IComparer(Of Stellung)
Public Function Compare(x As Stellung, y As Stellung) As Integer Implements System.Collections.Generic.IComparer(Of Stellung).Compare
End Function
End Class
Problem is: inside the function I have no access to any fields of my class. If I start off with x. Intellisense will only give me .Equals, .GetHashCode - the methods you get on a type but not on an instance. Visual Studio 10 also highlights this, in the definition of the function the bits "x as Stellung" and "y as Stellung" are written in light blue, meaning it is a type and not an actual object. How do I access the things I want to compare inside my class?
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Jun 26, 2009
I am creating a generic class that is Implementing IList(Of T) which requires that I implement the GetEnumorator of both IEnumerable(Of T) and IEnumerable. When looking at the members of IList(Of T) I see only one GetEnumorator function, yet it implements IEnumerable(Of T) and IEnumerable. How can I use one function to implement both interfaces when the function definitions only vary by return type?
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Jul 11, 2011
I'm migrating the CenterSnap.cls from its vb version to vb.NET and I'm confused about the following 2 errors after I import the vb6 project to VS 2008.
[Code]...
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Nov 18, 2009
implement singleton in a parent class. Infact what I want is that All the childs etc. should use same instance of the parent.
I have implemented singleton, Changed the scope of parent class's constructor to "Protected". But in the application when ever the new child's constructor is called i.e. "Dim abc as New Ch1()" the constructor of Parent is called (as it is Proctected and can be access from child). Which is undesired behaviour.
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Jul 19, 2010
[code]The reason that this is a problem is that this is a collection of EventBase objects, but I'm trying to populate it with child classes instead. For example, I might have a JumpEvent class that inherits EventBase, and this is being put into the EventBaseCollection. That means that value.GetType() returns the type of JumpEvent, which as you might guess does not equal the type of EventBase.The goal of course is to simply loop through all of the various events without having to know anything about the sub-classes. Is there a way to determine the type of the base class so that the OnValidate call will work? Or is this just the wrong way to go about it altogether?
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Jun 2, 2009
I understand that inherited classes can't be converted from base classes. But is there any way to write a conversion sub, so that the base class gets assigned to MyBase, then extra properties are added?[code]...
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Feb 3, 2011
In some DLL, I have an interface defined like this (shortened code):
Public Interface wsIInvoice
''' <summary>
''' Perform plugin specific actions for a given memberhip invoice that is processedin an incasso batch, and return success result.
[Code].....
The DLL implementing the interface has a reference to the one defining it. And the defining DLL is imported.
I'm doing exactly the same thing in another DLL, and there VS does not complain.
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May 8, 2009
I am having trouble with this project I am working on. I am a beginner to vb and have some background in access databases. I will attach my am doing an inventory project. When you execute the form, a main form pops up that allows you to choose Production or Inventory. My issue is with the Production. In the production form that pops up after clicking Production, there are text boxes to be filled out by the user based on the production run.plementing a class that will give the box count based on the box type entered. I have to use a class based on the project requirements.
Basically to calculate the usage, enter in a random number for Pods Produced, then enter in a box type (which is A box, B box, C box, D box, Master Case). I want the Public Class Box Count in the code to be able to be placed in the production form's main class code and calculate the box count based on the box type entered. If A box, box count should be 50. If B Box, box count should be 100, If any other box is typed in, the box count should be 150
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Jan 27, 2010
I am trying to design a table type structure that contains rows and cells. I intend the cell class to have a value property. I'm trying to work out how I can create a value that can return some defined different types e.g integer, single, date, string. I'd like the cell value to be strongly typed, but I am unsure how best to get this working.
My thinking in code so far:
Public Class Cell
Private _value as object
Public Property Value as Object // How can I define this so that it return a Type
Get // e.g. integer, string, etc
Return _value
[Code] .....
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Oct 21, 2009
I'm dealing a problem in implementing interface for multiple class.
Assuming I have a class named Class Unu .
I created an interface called Test for those 2 classes.
The first class Unu has 2 data members(i=12 and j=12.17). When you run the program it stores the result on screen 24.17
The second class called Doi has 2 data members(a=20 and b=32.17).
What I want now is to do the same thing for data members a and b so that it stores on screen 20+32.17=52.17
My problem is that I want to be displayed also the result for the 2 data members for the second class on my screen. I implemented the interface on class Doi but I cannot see why he isn't displaying me the second result 52.17.
What I must add to my code to do that?
Here's the full code:
CODE:
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May 9, 2012
I'm trying to work out whether every Class in an Inheritance chain needs an explicit Dispose(disposing As Boolean) method or, if a given Class has neither managed nor unmanaged resources to dispose of, it can be skipped for that Class - even if a latterClass does require a Dispose method to dispose of mananaged or unmnaged resources?
Here's two examples:
Public Class BaseClass
Inherits Component 'Component has already implemented IDisposable
[code]....
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