VS 2008 Inheritance And Events
Jul 8, 2009
I have a base object, with a event that can be triggered by multiple methods.Then I created a child object that inherits that base object. I want to be able to trigger that event in the new object; but I can't use RaiseEvent to raise a base-object's event.To get around this, I created a small method in the base object that takes the argument for the event and I just use it to trigger the event. Is this the proper way to handle this situation? Similarly, I could Shadow the event with a duplicate one in the child object.Is there a standard way to handle events across inheritance?
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Dec 15, 2009
I've not played with inheritance myself much as I've never really had a need to, but now I have a situation which to me seems the ideal time to learn. I'll explain:
This is a WPF application but that shouldnt make any difference to this question. Basically, I have asearch window that retrieves data from a database - I want this one search window to be able to retrieve any item (business object might be a better word than item) from the database and display the relevant data, rather than having a separate window for each 'type' of item in my program. So I have got 3 classes at the moment, ComputerAudit, ConnectionAudit, and SoftwareAudit and I want my one search window to be able to display any of these items in the listbox. Obviously there would only be one type of item displayed at once, so there wouldnt be a computeraudit item and a connectionaudit item displayed in the list at the same time, but there could be several computeraudit items displayed.
So I thought I could create a base class just named Audit and have those 3 classes I mentioned inherit from that, then I can specify the arguments to methods I am using as just being of type Audit (rather than using a specific type like ComputerAudit or SoftwareAudit) because then I should be able to pass around any of these items which inherit from Audit right? Well that doesnt seem to be the case so I'm wondering if I have misunderstood inheritance.
The problem I'm having specifically is that I have some methods which need to be able to accept any of my Audit subclasses but if I specify a generic List(Of Audit) then it wont let me pass in a List(Of ComputerAudit) for example. Is this because I'm using a List or am I just doing something fundamentally wrong?
EDIT: Found this page which confirms my suspicions that this is more to do with the List than general inheritance:[URL]...
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Jun 27, 2011
I am having trouble getting inheritance to work with the VB 2008 Express entity classes. I am a beginner with VB.Net and self-taught in VB6.0.I am able to pull data from an SQL Server data base into my application using the O/R designer. The data can be successfully queried using LINQ to SQL, either returning a single record, or multiple records or an entire table as a collection of the enty class type (so the problem is not with LINQ queries).
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Mar 23, 2011
I have two custom objects.On of them inherits the other one, appends few more properties and methods, ovverides some other.When I try to cast the Parnet Object to Child I receive an error that it could`nt be done.
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Jul 31, 2010
If I declare and instantiate an instance of class B within class A, how do I make instances of class A member objects/variables accessible from class B?
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Nov 26, 2009
In my application i will use a customized datagridview for all the application, so instead of adding the normal datagridview and changing the properties, i created an user control and changed the inherited to datagridview... This have a problem i can't use the drag and drop...
[Code]...
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Oct 13, 2011
I have been trying to implement the jQuery weekcalendar using .net. What I can't seem to figure out is why weekcalendar states events.events is undefined after I make an ajax call to a webmethod I created which returns JSON. Below is the relevant code:
[Code]...
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Aug 2, 2009
I want to make Keybord events and mouse events for learning and educational Purpose.
1. In Form any object like A "picture box" move by Arrow keys .
2. Picture Box Contain many Picture i want change Picture With next and Previos By Arrow keys.
3. I contain Voice of alphabet in Mp3.When i Press any button in textbox then its work.
4. Mouse Pointer Change My Own.
5. I click any Object or any thing By mouse its noice clicking sound like Tik Tik Tik.... Question No 3 is very hard to do . but not im possible
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Jan 11, 2010
i have a class call it clsFamily this class contains properties that make up a family object. This class works fine with no issues. Now i need a new class (called MyAccount) which contains 3 properties, an ID a user name and a clsFamily object. I have declared both classes as Friend from within my globals Module and define the clsFamily as family, however when i try to put this type within my 2nd class i get an error "Type 'family' is not defined" what am i doing wrong? i know i could get it to work fine by adding the ID and User Name properties to the clsFamily object but i need to define this as a new type of object as the ID and User name are not normally part of this class.
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Apr 27, 2012
how can I capture an event like a button click or timer event, if I created the controls at run-time?
Ex: Dim a As Button
Dim b As Timer
I want to capture the click event of the button "a" and the timer event of the timer "b".
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Mar 24, 2011
Is it possible to get events of httpwebrequest? For example when I make a post request, then in the events procedure I should be getting something like this in the following order say
connecting to website
connected to website
posting request
request posted
waiting for response
receiving response
response received
disconnecting
disconnected
Or how to I implement something like this with the webrequest?
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Mar 15, 2010
I'm using a DGV to show some data & I'm using the CellClick event to run some code when the user clicks on each row. But I also want to run some other code if the user double clicks a row, but the CellDoubleClick event never fires, the CellClick event just fires twice. Does anyone have any ideas on how to make both events work?
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Aug 17, 2010
I don't really know how to call this...Anyhow... I have two objects (for example, "A" and "B") of the same type/class. I have an event (for example, "Refreshed") in both objects. Is it possible, that when "Refreshed" fires in "A", it also fires in "B"?
Edit: forgot to mention - "A" and "B" don't "know" each other.
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May 3, 2009
Is it ok for me to have this event - firing on TextChanged for my BillingSame textbox
[Code]...
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May 2, 2009
I've got a series of textboxes that are bound to a dataset. I've got them disabled and will be hiding them. Then I have a series of check boxes related to each textbox. The user clicks the check box and I change the value of the databound textbox. Nice and easy way to bind check boxes to DB fields. Any way to create these relationships at runtime - basically creating the events that I'm hardcoding right here.
Private Sub IntprtLead_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) _
Handles IntprtLead.TextChanged _
, IntprtCheck.TextChanged _
, IntprtCons.TextChanged _
, IntprtSimul.TextChanged
Dim strValue As String = TryCast(sender, TextBox).Text
[Code] .....
I know I can loop through the controls on the form and find these "named" objects easily enough. Is it possible to have more "generic" event code and then create the handles relationships at runtime?
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Sep 19, 2009
In a reply to one of my posts, a user said I should create an event for Textbox1.TripleClick.So, I would need to create an event.My problem is, how do I create an event for a textbox so that the event shows up in the textbox events?
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Jul 26, 2011
When my form loads i create an array of richtextboxes. Since they're created dynamically i don't know how to do events like, textchanged or click, for each richtextbox. I'm pretty new to vb and to the forum. I'm not sure if i've posted this in the correct place on the forum if not apologies.
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Mar 20, 2009
Say I create a new button on a form through
Dim Button2 As New Button()
Button2.Text = "My new button"
Button2.Size = New Size(100, 100)
[code].....
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May 10, 2009
How would i go about detecting While the user is moving the mouse and also holding down the left mouse button. like they were drawing something with a pencil in paint.
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Jul 13, 2009
I want to be able to pull items from an outlook Calendar and display them in a grid viewthe issue I am currently having is it will not display any recurring events, this is what I have so far.
Dim app As Microsoft.Office.Interop.Outlook.Application
Dim calendarcontents As Microsoft.Office.Interop.Outlook.MAPIFolder
Dim x As Integer
[code].....
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Sep 13, 2010
i need help to delete a record in a database table in crystal report, after the report had been view from the new page and when the page is close. the report is done in vs2008 c#.
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Apr 19, 2010
I've been working on an application recently and it has exceeded the scope of a single form.I decided that it would be a good time to use an MDI container and split the interface up over a number of different child forms.As the application was written, there were a few different classes that were being instanciated on the original form.I've migrated these over to the MDI parent form so that I can allow all of the children to interact with them.The route that I'm going down right now is raising events on the child forms and watching for them on the MDI parent.The parent form is then doing whatever the child did to the instanciated classes in the past.
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Jan 15, 2010
I've got a StatusStrip...and I'm trying to initialize some code when it gets focus...so clicking on it should give focus to it right? I've tried the following
[Code]...
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Oct 20, 2010
Is there anything I have to do to trap wheel mouse events?I have a panel and can trap the MyPanel_MouseMove events but not the MyPanel_MouseWheel events.In VB6 you needed to add wheel hook & unhook commands - do I have to do anything for VB2008?
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Oct 21, 2009
I am new to VB but I want to find this out. For example there are two objects in my form and when I press W,A,S,D then Object1 should move Up, Left, Down and Right respectively. Object2 moves when I press the arrow keys. How do I make them move together and also separately depending on whether the key is pressed.
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Aug 5, 2010
Whenever we need to handle events, we do it by creating a method which handles the event. Without creating methods; is there some other ways of handling events?
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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 5, 2010
Is there a way to prevent the form closing event from executing if validation fails on a control? If validation on a control fails this stops the form from closing, but the closing event still executes. Scenario is user has focus in a text box, tries to close the form. Validation fails, but closing event is fired. I'm not sure how I can abort that event.
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May 21, 2010
i have created a list of buttons using the following
Dim Butt(20) As Button
Dim i As Integer = 0
While (i <= 20)
Butt(i) = New Button
Me.Controls.Add(Butt(i))
i = i + 1
End While
this means that buttons are created in the code and not on the form to begin with, so I don't know how to create an event for the click of a button in a list. Is it possible to do it with a parameter for i so that there is only 1event for all buttons in the list, and i is the button index array clicked?
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Sep 26, 2010
I try to catch the keydown event, but arrow keys don't fire this event, although I set KeyPreview = True. Arrow keys neither fire the KeyUp event. Not on the form or on any controls..
What is required to handle:
1. Arrow keydown or keyUp event with individual event handler based on mouse focus/hover (does the control have focus if mouse hovers on it, or it needs to be clicked?)
2. Mouse scroll events individually based on "mouse focus"
I don't actually need for the form... Since all the form is covered by controls.. But I need individually for different controls. Which are just buttons, labels and a chart control.
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