VS 2010 Handling The Parent's Events?
Jan 28, 2012
I am trying to make a UserControl or Component which can be dragged from the Toolbox onto a container control such as a Form or a Panel. Its purpose is to change the behaviour of that container. In particular, I would like to add functions to the container's painting and mouse actions. I DO NOT want to have to write code for the container itself -- that's the whole point of the Toolbox object.
I can do this by getting a reference to the object's Parent (or Host in the case of a Component) and handling its events, as this example illustrates:
[Code]...
However, I have heard that handling the events of a parent control conflicts with OOP principles. So I would like to know, does that objection apply in a case like my example? If so, what are the drawbacks? And what alternative techniques are available?
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Nov 23, 2011
I took a VB class a couple semesters ago and I did really well. Unfortunately, it seems as though we only covered the very basics within the class, as I feel rather clueless right now.
Here's my issue. I'm trying to write a program that will encode notes (like music notes, A-G#) which are entered by the user, into digits, 0-9. Now I have the system laid out, in that 1-8 will represent A-A, while a 0 or 9 preceding a digit will represent a flat or sharp respectively.
Now my question is actually rather basic, but I just can't seem to figure out how to do this. The user will enter the note sequence by clicking on buttons (12 of them). What I'd like to do is create one sub that will handle all possible button clicks. I suppose it's possible that I could have separate subs for each and every button; but it just seems more efficient and cleaner to have one sub that manages them all.
The part I have completed and working properly will display a message (the same message) in a messagebox each time any of the buttons are clicked. So I have the "Handles" part working for all 12 buttons. But what I'd like to do is write code, perhaps "If" statements such that If "btnA" is clicked, then say "You clicked Button A," and If "btnASharp" is clicked, then "You clicked Button A Sharp," and so on. Is it possible to do this somehow by recognizing which event was actually triggered?
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Apr 4, 2012
the question is really what is the correct convention (style) for raising and handling events. When a button is clicked it is generally handled by this method. [Code]
I have recently been trying to follow this convention by creating my own EventArgs class and inheriting the system.eventargs, Then adding my own properties. The problem is as my projects get bigger/complex I seem to be writing multiple eventarg classes. I then decide to try and create a generic eventarg class but this then seemed pointless thinking it would be easier just to pass the object directly instead of wrapping it up in "someEventArg" i have created.
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Jun 7, 2009
I'm calling the SQLDMO 8.0 COM library from VB.NET (using a PIA I generated with tlbimp) in order to backup a database with percentage completion notification:
Dim server As SQLDMO.SQLServer = Nothing
Dim backup As SQLDMO.Backup = Nothing
Dim restore As SQLDMO.Restore = Nothing
Dim backupAbortable As Boolean
Dim restoreAbortable As Boolean
[Code]...
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Jan 22, 2009
I have a component written in C# which exposes an event which the clients can Handle. I would like know how to handle this event in VB.Net?
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Nov 5, 2009
I need to write an app that that will iterate over our database, and perform various anaylsis on each record. In order to do this (partially for the learning exercise in creating plugin support) I want to use a Plugin model.
Currently, I have a simple Interface in my main app, which plugins can Implement. My app then loads all DLL's in a folder looking for ones implementing the Interface.
As you can see in the pseudo-code below, I have to keep performing a loop through all loaded plugins calling the process methods.
Sub ProcessData()
For Each Record In MyDataSet
For Each Plugin In MyPluginCollection
[Code].....
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May 12, 2009
I have some VB6 code that instantiates a class which handles events that are being raised from a VB.NET component. The VB6 is pretty straightforward:private m_eventHandler as new Collection
public sub InitSomething()
dim handler as EventHandler
set handler = new EventHandler
m_eventHandler.Add handler
m_engine.Start
[Code]...
My problem is that when I debug the VB6 program, the first time InitSomething gets called, the event will not be handled (the VB6 event handler is never entered). Subsequent calls to InitSomething does work.
Everything works as I would have expected when I run the program outside the debugger. At this point, I'm not even sure if this is something I should be worried about.It may or may not be relevant but the VB.NET was converted from a VB6 using the Visual Studio code conversion tool (and subsequently manually cleaned up).
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Nov 8, 2009
Work = New ExampleWork()Here the Work is a withevents variable and I've used the handles clause for handling various events fired by the ExampleWork object. However the event handler will not get assigned till the constructor of the ExampleWork returns. Now how can I handle any events fired from the constructor? I can move the constructor logic out to a separate method and call it after the constructor has returned and thus handle all the fired events including events fired from constructor. However it doesn't look good
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Feb 12, 2012
Handling Events For An Array Of Controls
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Apr 14, 2011
I am creating a program using Visual Basic 2010 Express.
I want to make a Sub handling both MouseHover and MouseLeave events. Is this possible? And if possible, how do I differ between MouseHover event and MouseLeave event?
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May 7, 2009
I would like to use MS Office automation and have event handlers that fire for user-triggered events. For example, if the user clicks the save button in Word, I want to intercept that event and execute code in my program.
I don't want to be bound to a specific version of Word because I don't know what version my user will be running, so I instantiate a reference to Word using late binding. The problem is that the AddHandler and the Dim WithEvents commands require specific references to an object that is known at design time. Given this, how can I define an event handler without having an early bound reference to a specific version of the Word library?
I can try to a reference to an earlier version of Word with the expectation that newer versions of Word will be backwards compatible, but this seems kludgey and risky.
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Aug 1, 2011
Assuming I have the following repeater.
[Code]...
But this has failed (The event is never raised)..
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Dec 3, 2010
I had a question about handling multiple events in a sub, like this:
Private Sub Form1_MouseUpOrDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Me.MouseUp, Me.MouseDown
'do something
End Sub
Once the sub is called, is there any way to tell which event called it? (Whether it was a MouseDown or a MouseUp event?) Right now, I am doing a work-around as follows... having each event call the same sub and pass the info in. But it would be nice to not have that overhead.
Private Sub Form1_MouseDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Me.MouseDown
ExecuteMouseUpOrDown(EventTypes.MouseDown, sender, e)
End Sub
[CODE]...
Don't use ACCESS, EXCEL, or a TEXT FILE as a database. If you want your program to use a "local database", without any of the hassle of setting up a MS SQL or MySQL server, just click this link: >>> SQLite <<<.
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Aug 10, 2010
I have multiple textboxes which I want them to perform the same thing upon clicking them. By default I can use the handles textbox1.click for 1 single textbox as shown below but I am not sure how to do handle multiples of them. Of course I can write a handler for every single textbox but I have about 50 of them. I am sure there must be a more efficient way. [Code]
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Mar 22, 2010
In order to take advantage of the spell checking ability of WPF textboxes, I have added one to a user control (with the use of elementhost). This user control is used in various window forms. My current problem is trying to handle keyup events from this textbox but the windows form is unable to "get" any event from the control. I can access the properties of the textbox just fine (i.e. text, length, etc.) but keyboard events don't seem to work.I have found, however, that the following will bring back events from the WPF textbox:
Public Class MyUserControl
Private _elementHost As New ElementHost
Private _wpfTextbox As New System.Windows.Controls.Textbox
[code].....
The user control is now able to do something after the PreviewKeyUp event is fired in the WPF textbox. Now, I'm not completely sure how to have the window form containing this user control to work with this.
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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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Jan 24, 2009
I am trying to create a ContextMenuStrip where I add a certain amount of ToolStripMenuItems based on how many columns are in a DataGridView via code. I am wondering, since I am creating all these ToolStripMenuItems in code, how would I handle the "CheckStateChanged" event on all of them separately? Or how can I figure out which one of those ToolStripMenuItems was clicked?
Here's a code example of what I mean:
Private Sub CreateCMS()
Dim CMS As New ContextMenuStrip
Dim TMS_Main As New ToolStripMenuItem
[Code].....
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Jul 24, 2009
[2005] Handling Events With ToolStripMenuItems Created With Code
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Jul 18, 2009
I'm writing a tabbed web browser for someone who is learning VB.NET, and I have got to the point where I can add/remove browser controls into tab pages, controlled by one set of buttons on the main form, but I can't handle events from the WebBrowser objects.I have tried this but it says that 'DocumentTitleChanged' isnt an event of 'Control'...
Dim browser As New ArrayList
browser.Add(New WebBrowser)
browser(0).parent = TabControl1.SelectedTab
browser(0).dock = DockStyle.Fill
AddHandler browser(0).DocumentTitleChanged, TitleChangedHandler()
I want to update the tab title with the web page title when it changes. I started using a timer to update the tabs but there must be a way to add an event handler here.
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Apr 26, 2010
come years ago I bought an activex component to read some basic smartcard data. I created a simple form application and it has worked fine ever since. However, instate of a form application I now want to create a console application for the same purpose (the forms are unrequired and it just takes too long with multiple smartcards).
But I have been working on this for days now and somehow can't seem to get my events working. When I use 1 event, everything works fine, but as soon as I add my second event I get this error:
Unhandled Exception: System.Runtime.InteropServices.COMException (0x80040202): E
xception from HRESULT: 0x80040202
at System.Runtime.InteropServices.ComTypes.IConnectionPoint.Advise(Object pUn
kSink, Int32& pdwCookie)
[Code]...
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May 19, 2012
I have various input textboxes on my form. And based on entries made in each of the input textboxes, I update the display textbox. However, using AppendText message of textbox. I have my input textboxes set to accept only numeric values. So for each character inputted correctly, I update the display Textbox. Problem I have is when user selects Key.Back or Key.Delete, what I would like to do is do a Delete of last character in the display textbox, but I am yet to get this right. How do I delete the last character in the string that is contained in a TextBox using AppendText()
[Code]...
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Mar 27, 2011
I am getting DragLeave Events when dragging from a parent to child control. I would only expect to get this event when moving outside the bounds of a control. How can I implement this?
[Code]...
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Mar 10, 2010
I have a user control and a panel on it in Dock fill format. Now this is exposed for the user to add on the form. Till this point fine. Now the user sees lot of events for the user control, which I want to actually link up with the panel on the usercontrol, because that is where I want things to happen . Is there any solution to link up the events in few lines of code than calling each event separately? I am also looking to expose only few events than all the base control events.
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Sep 8, 2009
I have an object, say Order where if an error occurs, it raises the ErrorOccurred event. If I'm running some code in say, the codebehind for a .aspx page with an public Order registered as WithEvents and I want to check to see if an error has occurred before I run more code, how do I do this? I can't simply check theOrder.ErrorOccurred. Do I have to create a local boolean flag that switches over in the event handler (OnErrorOccurred)?
Example:
Public WithEvents theOrder As New Order
Public Sub DoStuff()
theOrder.DoSomething()
If theOrder.ErrorOccurred Then
[code]....
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May 1, 2009
long story short, I have created a ListView type control, using UserControls for the parent control and the ListViewItems. Most the of the control is written and works fine, right up to the point where I tried to replicate the 'Control.SelectedItems(0).Index' property and the 'SelectedIndexChanged' event.
Each child object knows its index value, and could pass this value via the SelectedIndexChanged event (assuming this is how it works in a normal ListView control -- user clicks on an item, and that item fires an event updating the selected index value in the parent object).
How does the child object raise an event in the parent object? I have a feeling this could be done with Delegates, but I'm still learning about their usage.
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Jun 3, 2012
I used the following code(with bug):
Code:
For n = 0 To 100
If saveLine(n).Substring(0, 8) = "heading:" Then
cboSelect.Items.Add(saveLine(n).Substring(8))
End If
Next n
The For loop only ran 5 times. It turned out that saveline(5) was shorter then 8 characters, so I changed the code which solved the problem:
Code:
For n = 0 To 100
If saveLine(n).Length > 8 Then
[code]....
VB 2010 neatly exits the for loop when the bug occurs. In this case it was easy for me to pick up the bug, because the combo box was not properly populated. What if it was not obvious that the for loop did not complete? It is quite scary to think that bugs like this are not displayed at run time.
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May 10, 2011
Anyone out there who happens to have an exhaustive code snippet for SEH (including all possible exceptions) for VS 2008 or VS 2010 (.NET 3.5 or 4.0) ?
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Oct 18, 2011
I have a sub which creates an XML file but the thing is, all the parameters are 'hardcoded', so I decided to give some inputs so each data in each node is customizable. Now, I would like a loop to read the text in textbox1 and assign that to variable one, do the same for textbox2, write the node, loop again (using the same variable) and assign that variable a value in textbox3 and write the node.
I can while loop to write nodes, but only for fixed data or data with 500000 variables for each loop. Is there any way to do this such that on each loop it dynamically sources the variables data from the 'next text box'. i.e. One first loop uses textbox1, second loop it knows it has used textbox1 .'. it uses textbox2 etc... Is there a way to do the same thing but write back to text boxes in an order, knowing what was previously written.
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Aug 29, 2011
How does one handle unhandled exceptions in a DLL? VS doesn't give me the option to add Application Events, I'm guessing because it's a DLL. Do I just have to do it in the main app?
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