C# - WINFORM Or WPF: Trigger Custom Event Inside The Constructor Of The Class That Emits It?
Nov 17, 2009
I have a userControl11 (either in winform or wpf) which has a ValueChanged custom event. If I put it in client form and in form_load set its value to 100, it will trigger the ValueChanged event. But if I set this value inside the constructor of UserControl1 the custom event won't trigger. How can I force it to do so ?whatever the technical reason, functionally it does make sense. If the object is initializing its value from some sources unknown to the client form and the client form has a textbox bound to this usercontrol value, it is sure convenient that it could refresh its textbox at any time including when the form loads just using one single event handler. Without this the client form has to create another initializer for this bound textbox at form load.
Below the source code of my trials in winform:
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
[code]....
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Mar 1, 2010
I have a custom collection class that I would like to pre-populate with data from the database. Basically it would search for "submembers" that are related to the "member" data record using the "member"'s primary key id.
I figured the best way to do this would be in the constructor of the class, but I am not so sure now. The collection class does not have any properties (the member class does).[code]...
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Mar 12, 2010
I'm making a class that reads a file and processes data in it, but I need some error handling. I'm giving it a constructor that takes a file location and processes that file. How can I make it so the constructor tells the program whether it found the file or not? Optimistically the program that calls this class would check for that first, but since I'm not going to be the only one that uses this class I'd like to know how to secure such a thing. It's probably bad practice to do this within the class, but I'd like to be sure it's as portable as possible.
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Jan 31, 2011
I want to create a custom class that has inside an array of another custom class (see my code below) but when the programm runs is crashes. Why? What is the right expression???? Plz help I'm a newbie in VB.net.....
Public Class ctrarray
Public nameclass As String
Public ctrlindex(glvar_spaces) As ctrlindexclass
End Class
[code]....
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Jun 5, 2009
In .NET I have a class called Caption. I have another class called Gauge. Within the Gauge class I have a property defined as a Caption.I am trying to figure out how to do thefollowing:When a certain property is changed in my Caption class how do I get it to execute a subroutine in the Gauge class? I am thinking I have to declare an event and AddHandlers to fire it off, but I can't think of how to accomplish this.
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Jun 4, 2009
I read some articles about using events and/or class events, but not a single article realy explainend the true use and benefit of using events in classes, but only how to use them.
As far as I understand, you can use an event to trigger a certain procedure of a class within another class or aspx page, but you can do the same by declaring an object of that class and call de procedure or methods directly. why and when or where we would use an event with addhandler to call a routine from a class and not declare an object of the class and call the desired routine directly.
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Oct 26, 2009
I discovered that an event raised (directly on indirectly) in the constructor cannot be handled outside the very class. To prove if that was the actual problem, I wrote a simple exemplary app.
Class with the event:
Namespace Utils
Public Class A
Public Event Test()
Public Sub New()
CallTest()
[Code] .....
The reason of such behavior became quite obvious after writing those pieces, but maybe there is a way to omit it?
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Feb 18, 2012
I have a main form that has a dynamically generated treeview and also a panel control. Depending on the selection made within the treeview the panel docks 1 of three diffrent usercontrols which are full sub forms(done for ease of modifing design of sub form rather than layering panels on top of panels).Upon button click withing usercontrol i wish to trigger event within main form.For example delete button wich then triggers to remove current selected node from treeview. code for 1 of three diffrent user controls
Dim ctrlQ As New QuoteUC(TrViewQuotation.SelectedNode)
PnlSubFormDock1.Controls.Add(ctrlQ)
Code for delete button for which i need to raise event.
If MsgBox("Are you sure you wish to delete this customer ?", vbYesNo, "Delete Record") = vbYes Then
Deletecustomer(n)
End If
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Feb 15, 2010
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.
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Apr 14, 2009
I have a "partial" class in VB.NET. Half of it is auto generated by a code generation tool. That half implements INotifyPropertyChanged, so any properties in that part of the partial class raise the PropertyChanged event.In my "custom" part of the class, I declare another property that depends on one of the properties in the auto-generated side. Therefore, when that auto-generated property changes, I also want to raise a PropertyChanged event on my custom property that depends on it.
If I go into the generated part of the class and raise the event there, that will get overwritten if I ever re-generate that part, so I don't want to do that. I would rather add an event handler in my side of the partial class that checks if the generated property changed, and if so, raise another event for my custom property.
[Code]...
I'm assuming it's because normally you'd use the WithEvents keyword to tell the compiler that you're subscribing to events from that object. I don't have a clue how to do this inside of the class that's actually raising the event, or if that's even possible.
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Oct 14, 2010
I have created a dialog as a winform and am calling that winform like this:
Dim dlgEditChangeOrder As New dgEditChangeOrder
Dim dlgResult As DialogResult
dlgResult = dlgEditChangeOrder.ShowDialog
pretty simple. I want to be able to set the visiblility of a control on the win form when the win form is called. I would like to do this as a constructor so I could write the following. Dim dlgEditChangeOrder As New dgEditChangeOrder(visibleIsTrue)
Can someone give me the contructor code to make this happen? The reason I am concerned is I dunno if its legal to do this inside a winform since the winform is loaded bby the precreated IntializeComponent() function
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May 31, 2012
I was asked to build a winform exe that receives arguments from a web service and decide in which mode the application should start.what is the best way to design and build the application?The application needs to receive 3 arguments.
User name. - stringApplication mode - Boolean (user read write privileges)List on string.
Where do I receive this arguments in the new method ?
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Nov 14, 2011
I have a Windows Service project designed to monitor an email account and make entries into a SQL Server database when certain emails arrive. This is a rewrite of a similar winforms program that works just fine, except that it requires that the computer be logged into an account and the program started manually, which I can avoid by using it as a service.In the service I maintain a list of logged messages - basically just a string and a timestamp indicating that something has happened. (That list is shared out over a WCF service but I think that's immaterial, at least at the moment.) In my custom class I declare a public event, and elsewhere I raise that event. For some reason, though, the RaiseEvent isn't being run in the service. For example:
[code]...
The problem in this case is that _pc_HandleEvent isn't ever being called. If I duplicate this setup in a regular winform program, everything works like it should. What am I doing wrong? How do I get a service to handle events raised from other classes?
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Jul 24, 2010
I have a custom class which basically manages the program settings.
In it's New() event, I'm performing a check to see whether a value stored in My.Settings is the same as the default value (I made sure the value wasn't!), if not then it will perform a RaiseEvent ValueChanged().
On my form, I have an instance of the class declared "Private Withevents ProgramSettings as New clsProgramSettings", I also have a handler "Private Sub DoSomething() Handles ProgramSettings.ValueChanged" declared.
When I run the program the form gets loaded, the instance is created, the RaiseEvent is called, but the handler is not receiving the event?
I tried "Private Withevents ProgramSettings as clsProgramSettings", then creating the instance in the Form.Load(), but still no success!?
Is there something I'm doing wrong, or is there a problem with the IDE? I'm using VS 2010.
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Sep 24, 2010
I'm having an issue where my main form isn't updating even though I see the event fire off. Let me explain the situation and share some of my code which I'm sure will be horrible since I'm an amateur. I created a class to take in the settings for running a process in the background. I add some custom events in that class so I could use that in my form instead of a timer.
[Code]...
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Feb 12, 2010
Eg. ""vb.net" timer event trigger on purpose". This application is meant to run at all times to download a web page every minute. To avoid freezing the UI, I read that the best solution is to move the code from a While/Sleep loop to a Timer that will be triggered every minute. The problem I have, is that the user must wait for a minute before the event is triggered:
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Timer1.Interval = 60000
Timer1.Enabled = True
[CODE]...
Is it possible to force this event to occur instead of waiting for it?
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Nov 16, 2011
I have a BackgroundWorker in a vb.net program that is doing a lengthy data import routine. I want to modify its RunWorkerAsync method so that it fires a custom event on completion of the method. (So that a method in an automated process can respond to the event and resume its work). In a sense I want to 'extend' the RunWorkerAsync method to add an extra line of code--but I can't 'see' the code in the method (to just add the line raising the event) because BackgroundWorker is an MSDN class from Microsoft.The only solution that I can think of is to 'wrap' the background worker class in a wrapper that calls the .RunWorkerAsync method and then raises the event.
Public sub wrapperMethod()
myBackgroundWorker.RunWorkerAsync()
raise customEvent
end sub
Is there a design pattern that I might use? An easy way to address this with the .net language?
PS: Unfortunately, I'm automating some clanking legacy software and backgroundworker is used in many locations, so wrapping the backgroundworker will be a bit of work and may open bugs.
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Jul 29, 2009
I've created my own ascx control with button inside it. Now I'm using this control inside other control. (In my case it is a webpart). What I would like to do is program button.click logic from my custom control inside webpart
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Aug 18, 2009
I have some classes, BsfciFile and StudyFlashCard. Bsfci is the extension to which I save my set of flashcards in an INI format. I am currently working to transform my code from using Windows API calls to access the INI to using a IniFile class that I found on the internet. I would like the BsfciFile to have a Array of StudyFlashCard objects, but I would like the StudyFlashCard class to use the IniFile class object contained in the BsfciFile class. I can pass the IniFile from the BsfciFile class to the constructor for the StudyFlashCard class, but I want it to modify the same IniFile as the BsfciFile class has later on.
[Code]...
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Dec 21, 2009
I am using Expresion Blend 3 and created a new user control in my project. I want a storyboard to run if a custom property of that user control is triggered like with the ones shown here in the list..
I learnt you need a dependency property, but my understanding there is limited. Here's the basic code I set up with property "IsAwesome" as an example[code]...
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Nov 20, 2009
i need to be able to drag and drop my picturebox with an image in it around my winform in vb.net.
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Jun 8, 2010
I have a directory named reports inside my winform project in .net. My project name is AccountingReports and inside that Directory reports exists. So i need the way to access this path via code. In Asp.net we use Request.PhysicalApplicationPath property. So is there any method or property exists that will give me the root of my project
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Oct 29, 2009
I am trying to open a word template inside a form in my vb.net application but I cannot seem to find any guidance to doing this. I do not want to call microsoft word to open in order to see/read/write on my template. I want the word document to be within a form I am creating like a print preview sort off. I am using Word 2007 and VS 2008. I have been using so far automation and calling and interacting with the template but until so far I have to open Microsoft word to open it for me.
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Oct 29, 2009
I am trying to open a word template inside a form in my vb.net application but I cannot seem to find any guidance to doing this. I do not want to call microsoft word to open in order to see/read/write on my template. I want the word document to be within a form I am creating like a print preview sort off. I am using Word 2007 and VS 2008. I have been using so far automation and calling and interacting with the template but until so far I have to open Microsoft word to open it for me.
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Feb 19, 2012
I have this code in my ViewProductsInventory (which is called from my MainForm by ShowDialog):
Private Sub ViewProductsInventory_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Me.Tb_inventory_datesTableAdapter.Fill(Me.InventorySysDataSet.tb_inventory_dates)
Dim inventory_date As Date
inventory_date = Me.cboInventoryDate.Text
[Code] .....
Upon clicking the editbutton will execute EditForm.ShowDialog()
And in my EditForm the record will be updated, after which will trigger ViewProductsInventory.btnSearch_Click( ViewProductsInventory.btnSearch, EventArgs.Empty)
And then the error "Conversion from string "" to type 'Date' is not valid" occurs.
I tried Msgbox(Me.cboInventoryDate.Text) and returns nothing. I'm assuming that my cboInventoryDate is not being populated at this time therefore when btnSearch_Click is triggered it receives nothing.
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Jul 31, 2010
I try to sent an event to trigger the parent.Why doesn't the event arrive?Event is public Handler added to parent.
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Nov 29, 2009
I am trying to build an add-on for some software. they are done using vb.net
I want to trigger an event called project selected but dont seem to get the option.
Ive selected the control but the event doesnt appear in the options list i can override the event by doing a Addhandler myControl.ProjectSelected, AddressOf newEvent is there any way in my newEvent method to run the orginal ProjectSelected event ??
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Jan 27, 2010
I have a set of accordian divs (powered by the prototype library) in an asp.net page. I would like to save the state of the accordian, so when a postback event occurs, the same div is open rather than reloading the page entirely and opening the default div.
My plan was to set a page control value with the ID of the open div using the div's toggler click event function, and then fire a click event after postback calling that same div (using the value of the control holding the div ID) as the target. I'm not sure how to fire a javascript click event from vb.net however, and this sure seems like a lame workaround.
1) can you tell me how to fire a javascript click event from the vb.net codebehind page
-or-
2) is there a more elgant way to do this?
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Mar 29, 2009
i am trying to allow a user to press enter in a text box to trigger a text change of an object...
1. say u put 2 in a text box called "Number" and
2. when you press enter,
3. another object named "penbutton" to change it's text, that u can see on the picture to "write"..
4. originally the book will have the text "Start" on it
do i changed the "number text box" enter event ? how do i do this? This is what i have so far
Private Sub xNumberTextBox_Enter(ByVal sender As Object,
ByVal e As System.EventArgs) Handles xNumberTextBox.Enter
Me.NumbertextBox.AcceptsReturn = True
[Code].....
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May 3, 2012
I have a project with many forms on it, some of them are dialog forms, some of them are mdi children of my master form. What I need to do is when a user press the ESC button on his keyboard to dispose the form that is working on. either is mdi or dialog form. I know that I can use the event of the form key down and then check the key code if is the esc to dispose the form, but this is not I looking for since I will have to pass from all my forms and create that event. Is there any other way when my master form is load to create my own event for any form load event? And trigger it from there to assigne my custom code for ESC key. So I will not have to pass from all the forms to create that event.
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