I want to add a handler to an event in vb.net through a constructor .... i thought i would be able to do something like:
vb
Public Sub New(Optional ByVal PreDraw As [Delegate] = Nothing)
If PreDraw isnot Nothing then AddHandler Me.PreDraw, PreDraw
[code].....
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.
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]....
In java the constructor is as follows
[Code]...
can i make 4 constructors with diffrent parameters. now in vb how can i write constructor with parameters.
I'm doing a lab for school, and I came across something I have never done before: create a default constructor within my class. It involves creating a private field to store the connection string, then create a default constructor that sets the connection string.
Here is what I have so far:
Public Class Appointments
Private sqlconnection As String = ConfigurationSettings.AppSettings("ConnectionString")
Private Property connectionstring() As String
Get
Return sqlconnection
[Code] .....
Can someone help me with the code for an Event Handler for colorAnimation in VB.net. All I get so far is code in c#, which I do not follow very well. Please also show how to call or raise it from a control e.g. a button.
View 8 RepliesHow can i add one more parameter in System Events for ex : I want to add a parameter in Button Click Event.
View 5 RepliesI've recently learned a new trick. I never realized you could write a sub and then handle multiple controls' events right in the sub.instead of handling each controls click event, for example.
[Code]...
So I have a LostFocus handler for my TextBox, and it gets called whenever I press "m", "o", or "-". Why is that? [Code] Is all that's there. I thought that I might have access keys or something interfering, but I would have to be pressing Alt, "-" wouldn't work, and there's also the fact that I have no access keys on the form. What's happening?
View 7 Repliesif you have this in your Application events: Private Sub MyApplication_UnhandledException(ByVal sender As Object, ByVal e As Microsoft.VisualBasic.ApplicationServices.UnhandledExceptionEventArgs) _ Handles Me.UnhandledException 'test to make ceratin handlers both fire Debug.WriteLine("AppEventFired") End Sub nd to test it you do this
Throw New Exception("1") shouldn't the Debug.WriteLine("AppEventFired") line execute? It isn't that I can tell and I have checked that I am running in Debug, not Release.
Perhaps surprisingly I haven't added an event handler programatically before and I'm having trouble getting my head around AddHandler.I am creating a series of DataGridView controls in a loop and want to subscribe to the CellFormatting event on each of them.The event handler signature is as follows;Private Sub ConfigureRows(ByVal sender As System.Object, yVal e As System.Windows.Forms.DataGridViewCellFormattingEventArgs)This works fine when I enter it in the visual editor properties box but I can't figure out how to give it the correct arguments using AddHandler.
View 2 RepliesI have this code
If e.KeyCode = Keys.D0 Or e.KeyCode = Keys.D1 Or e.KeyCode = Keys.D2 Or e.KeyCode = Keys.D3 Or e.KeyCode = Keys.D4 Or e.KeyCode = Keys.D5 Or e.KeyCode = Keys.D6 Or e.KeyCode = Keys.D7 Or e.KeyCode = Keys.D8 Or e.KeyCode = Keys.D9 Or e.KeyCode = Keys.Oemplus Then
[Code]....
The output WILL be 189 when I press the - sign. But when I check "Keys.OemMinus" it stands for 189 and when I replace "Keys.OemMinus" with 189 it won't work either!
I checked the Resources file and it's correct. The picture just doesnt change, only shows the last pressed button...
Simply stated, I want to call the Panel1_Paint event handler from the Button1_Click event. Is this possible? If so, How? IE: Click the button and it paints the panel.
View 6 Replies[Code]....
I've tried several variations of this. If the Cancel button is clicked on the dialog, an exception occurs, and a crash in an executable. I thought the "Exit" statement would take care of it. Not true. What I need is an error handler. In VB6, I used "On Error". I would prefer to not do that here.
I have created a WebBrowser and I want to catch the page that says "This program cannot display the webpage " instead of loading that page I want to display my own html code for that error. And also to catch error when loading an html page from a disk which is not present at all. (file not found)
View 7 RepliesI have a simple, but important question: How can I raise events of my form1 on another module/form?My form tempalte is crowded with events (50 of them contextmenustrip events)How can I place those events on another form/module to clean it up a little?
View 7 Repliesto know if a control have any handler. I have a dgv and in the editing control Showing event i add an event handler like this: VB AddHandler e.Control.KeyPress, AddressOf Grid_KeyPress_NumbersOnly This event it's added in some of the columns and for the other ones i remove it... The problem it's when the user, for example selects 3 columns where the event it's added, then if the user selects one where the event it's removed, it doesn't remove all handlers... So i have 2 solutions, when removing i put multiple removes or the other check if the event handler it's added doesn't add again. I prefer this second option, but i don't know how to check if the event it's added?
View 3 RepliesWith reference to my previous thread on Paint event handler.. [URL] I went to read up more on Paint Event Handler.. I have a button which draw out a path based on the user selection.. Below contains the drawing of the path portion of the button click event code
[Code]...
However It did not activate the paint event when I clicked on the button.. Instead, the paint event still activate even before I click on the button? So can anyone teach me on how to activate the paint event when I click on a button?
I am teaching myself VB, and when I try to run this program, I am getting "An error occurred creating the form. See Exception.InnerException for details. The error is: Object reference not set to an instance of an object." If I was to declare the variables inside each event handler, the program runs, but why won't it run when I make the scope public? Seems repititous having to declare the variables in every event handler. [code]
View 7 RepliesHow do I get a Event Handler to fire from within a nother Event Handler?
View 6 RepliesThe event handlers in my parent class are never called though the events are raised in the child class.
The Code:
Public Class childForm
Public Event checkboxchangedEvent(ByVal checkbox1 As Boolean, ByVal checkbox2 As Boolean)
Private Sub checkboxchanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles CheckBox1.CheckedChanged, CheckBox2.CheckedChanged
[code]....
remove an event handler from within the event handler?
I have a class that gets data from a hand scanner. When the scan is complete and the data is validated, the class fires a custom "ScanComplete" event and returns the data in a custom EventArgs.
In the calling program, I'm creating an instance of the scanning class and adding a handler for the "ScanComplete" event. In the event handler I get the data that was scanned and then remove the handler.
It seems to be working but it feels wrong to remove the handler while I'm running inside the handler. Will this cause a problem?
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?
View 3 RepliesA 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].....
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
View 5 RepliesDo 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].....
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.
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?
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?
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]....
