I have a base class foo that will be used in multiple child classes of similar but slightly different function:
Public MustInherit Class foo
Public Function bar1() as Something
''// Perfectly OK to change what this method does
[code]....
How do I get the compiler to generate an error when bar2() is overridden by a child class?
How do I access the base class inside a derived class?
View 1 RepliesI have written a function inside a class file which I added to my project in VB 2010 Express. Unfortunately, when trying to use this function in the main project, it cannot be seen by the compiler. The function is public. You can probably see from this that query that I don't know much about OO programming (I am assuming that the problem stems from something to do with this).
View 10 RepliesI wand to Expose a function inside a module in my Class Liberary( DLL)
module Module1
Public Function Add(val1 , val2) as double
return val1 + val2
End Function
End Module
i'm accessing an access database and want to execute the following query
INSERT INTO sometable
(date, field1, field2)
SELECT ( ? AS Expr1, field1, field2)
FROM othertable
? is a date i generate in code and field1,field2 belong to othertable i put it in a tableadapter and execute it by me.tableadapter.queryname(calculated date) but i get the error : Too many arguments to 'Public Overridable Overloads Function queryname() As Integer' Also if i try to generate the date in the query builder in the form dateserial(year(now),month(now),1-1)the query builder does not accept it?
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?
Yesterday I started my first DLL project which is for ArabicMessageBox that will allow arabic programmers to display there message in totally Arabic message.My project contain one Form only, and the basic code that I use is:
Public Overridable Function Show(ByVal APrompt As String) As MsgBoxResult
mLoad(APrompt, MsgBoxStyle.OkOnly, "")
Me.ShowDialog()
[code]....
I'm following this tutorial: [URL]..except I'm connecting to my own data source - a MS Access database.This is the query I have setup with the dataset:
SELECT Terminal_ID, SUM(Transaction_Quantity) AS Total
FROM tblTransaction
WHERE TransactionType_ID=3 and Transaction_DateTime>[@fromdate]
GROUP BY Terminal_ID
The debug fails immediately because it needs the extra parameter so I change the code from:
Public Class Form1
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
'TODO: This line of code loads data into the 'tetrisDataSet.tblTransaction' table. You can move, or remove it, as needed.
Me.tblTransactionTableAdapter.Fill(Me.tetrisDataSet.tblTransaction)
[code].....
The error I get on build is:Too many arguments to 'Public Overridable Overloads Function Fill(dataTable As tetrisDataSet.tblTransactionDataTable) As Integer
...I gave it the extra parameter, so what gives? Something special I need to do as it's a datetime field?
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.
View 5 RepliesI am writing a program and i need to declare matrices but there will be a different number to declare everytime the program is run so I was wondering if anyone knew how to declare them inside a for loop
eg.
For i = 1 to NumberOfMatrices
Dim matrix i (5,5) As Double
Next
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]...
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]...
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)?
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]...
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".
View 1 RepliesSuppose I have piece of code like this:
Public Interface ISomething
....
End Interface
[code]....
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?
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 ?
When I am writing a sub or function that does some calculations etc. I often need a loop or a integer variable to count.
An example:
''' <summary>
''' Compare elements with the new data and perform all necessary actions.
''' </summary>
[Code]....
As you can see, variables like timespan, nullCount and seconds are declared within this sub.
My question is, is it better to declare these in the class? I can imagine that would boost performance.
Ok, basically i have 3 different classes: one is a NormalUser, one is a SuperUser, and one is an Administrator. I have on one of my form loads an if statement like this:
If frmLogin.lstCurrentUserData(frmLogin.lstCurrentUserData.Count - 1).Contains("Normal") Then
Dim player As New NormalUser
[Code]....
So based on an item in a list, i want to create a new instance of that class to be my player. now i know that code doesn't work, because the variable is only present within the if statement. my question is, how can i declare "player" as a new instance of the correct type, and still be able to access it in other subs?
What's the advantage of declaring a function as "Shared"? I've noticed that it doesn't require you to instantiate an object to use the method when it declared as "Shared". Is that the only upside?
View 3 RepliesI had a problem with CLR profiler. But it worked eventually and the results were outstanding. My app took 47 milliseconds to run before and after some adjustments CLR profiler runs in 6 miliseconds! This had to do with String values in a resource file which apparently takes a lot of time. So this got me thinking, isn't it more effective if you would declare 1 String at the top of your class and constantly change it throughout your code? Instead of creating a new String in a method when you need it.
Instead of using:
Dim text = "blalblalba"
You would do this everytime you needed a string:
text = "blalbla"
My question is... What exactly happens when you say text = ""? Does .net create a new String? It looks like you replace the text but what happens in the background? Would it be faster then declaring a new string?
What's the proper way to declare variables in a class? I've been doing something like:
'in a class
public shared teststring As String = "first"
'on a code behind
[Code]....
with shared variables loading a second window or reloading the page (without clicking the button) renders the hello world string. so how do I declare variables in a class but make it per instance?
I'm trying to develop a class in VB .NET in order to manage a language globalization stored in a database and editable by the user.What I need is to know what kind of class I need to declare in order to use it without declaring a new object. For example, the way My.Settings is used.
One of the goals is that in some project the developer imports the reference and after that access directly to a property. For example: My.CustomLanguage.GetWord("Hello") without declaring objects.
Is this possible? And if it's what is the best way to aproach it?
[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?
View 2 RepliesI 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]...
View 7 RepliesI want to set my tcpclient up as a function and declare the ip and port later. However It wont let me. this is not copy and pasted code due to security reasons I wrote this code as theoretical cause I can not discuss the nature of my work. I am using vb.net 2008
I have
[code]
imports system.net
imports system.net.sockets
imports system.ipaddress
[Code]...
I have created my own ListViewItem class, and added some custom properties to it of attributes. What I have at the moment is a tooltip which shows all of those custom properties (about 18 of them).What I want to be able to do is if multiple are selected, to show a tooltip, but if a property (say Title) for all of them is "My Title" it will show that, otherwise if they are different, I would like it to show "VARIES"Is there a way of declaring a parameter in my function and return a value? [code]
View 1 RepliesI have a class that I would like to link at construction to a given control (say a textbox)
I know I can put a variable into a subroutine referentially but is there a way to store it in the same capacity?
I've decided to forget the d@mned custom code because everything I do with comes up with errors I don't know how to fix and it seems no one else does either. Or they do and they're keeping to themselves.
I put the functions that I needed to use in a class called MsgBoxOperations. The file name is MsgBoxOperations.vb In the report, up on the standard bar where file, edit, view, and all the other stuff is, is one that says report. You click that and go to report properties and it brings up where you can name the report and put in custom code...(hate custom code right now...) and where you can put references and class instances. Clicking on the Reference tab brings up wher you put in your references and classes.
In the classes area it asks for the Class Name, which I put in MsgBoxOperations, and the instance name of that class, this case mbo. I get that far and put in those two things and save it. Then I go to the textboxes where the values need to be. I put in the text box: =Code.mbo.GetStartDate
I've already tried taking the Code. part out and it screams that mbo isn't declared. So it does have to be there. I go to run the code and comes up with this error: QuoteError in class instance declaration for class MsgBoxOperations: [BC30002] Type 'MsgBoxOperations' is not defined.
I've posted before and still have received no help or someone tried to help but then stopped when their suggestion failed and then no one else wanted to help. I've googled this problem to the point where every link that it comes up with I have already clicked and found their information useless. I've got a freaking migraine because of this issue and have been in tears over it more than once.