We have a question regarding VB.Net 2008.
We are used control array in vb.net and third party timer controls.
When handle received from external application to timer control event procedure,
after this form becomes blank and controls disappear.
What we have to do to persist the controls.
You asked what you have to do to persist the controls. It's not clear whether you mean winforms or webforms, but I can answer for both possibilities:
If it's the former, you have it backwards. The default behavior of all controls is that they are "persisted" until you tell them otherwise. If anything disappears, it's because you have code somewhere that tells it to. That's where you need to start looking.
If it's webforms/ASP.Net, the problem is that you don't understand the page lifecycle. Everything that raises server events, including your third party timer controls, causes a post back. That's how events work - the browser posts the form back to the same url in such a way that the server knows to call a your event code at the right time. The thing here is that as far your server is concerned, it's still just a new http request, and that means you're working with a brand new instance of your page class every time this happens. If you've previously added some controls to your page, it doesn't matter. That was an old instance that was discarded and probably disposed by the time the page was visible in the user's browser. If you want to keep those controls, you need to make sure you add them to the page on every postback.
Related
We have a huge application that runs through a mass of code for every click you do. In one specific case, where you have a specific control in plain sight (so that the events are firing) and you load some special data into it and then click on the new button the form loses some events, like the closing event (you cannot close the form anymore and stop points in debug mode are not triggered) and one validating of a ComboBox that is really needed for the program. The only thing you can do when you get this kind of error is to restart the application to get out of this subform. But I tested it for 2 days now and even when I activate all points in the 'Exception Settings' I don't get any exceptions. The form (and other controls) are not losing ALL events. The resize, for example, still works. Even a specifically called AddHandler is not firing. Can you iterate somehow through the EventHandlerList? Or is there any way to test WHERE the event dies? Somehow any ideas on how to debug such a problem?
In VB.NET, is there a way to execute code after any event for which I have written an explicit handler, other than placing a call as the last line of each individual event handler? In ASP.NET I can put code in PreRender but there is no equivalent of that in VB.NET because there is no page life cycle.
I understand that for desktop apps the model is very different and that PreRender doesn't fit the desktop model but I hoped it would illustrate what I meant. In ASP.NET I often determine whether controls are visible, or enabled, in PreRender, after events have been processed and the underlying database has changed as a result. It seems reasonable to want to do something similar in VB.NET - multiple events can alter the underlying database, and multiple controls may need refreshed as a result, so write a routine that determines the visibility and enablement of the controls, and call it after explicitly-handled events have been dealt with.
I've tried the form validating/validated events but can't make them work.
I have a page on my web application which has a chart that gets retrieved using a timer. Is there a way to avoid the flickering everytime the chart is redrawn?
Since It's a web application, I guess the doublebuffer property isn't available, or at least I didn't find it and assumed it's webform related.
I would appreciate any help in the matter.
A quick and easy but not suggested solution is to call the redraw manually and remove the event.
So you would remove the event handler and you call the function that redraws the chart when you think is required. i.e After the resize is done or after a value is changed etc.
Since it is a web application, I guess the redraw you are talking about is made using a browser page refresh.
If so, you should take a look at Microsoft Ajax Framework, and a UpdatePanel control to just refresh the specific chart part of your page. Should be smoother then.
http://www.asp.net/ajax
I have a webbrowser control that points at a webpage that holds some fields that change quickly. When these fields change the server seems to request that the webpage refreshes. This poses a problem if programatically interact with the webbroswer. Is there anyway to force the webbrowser to not refresh? No real code to show. since I'm hoping this is a one line property I can create/add.
Maybe you are looking for the WebBrowser.Stop() Method (MSDN)
I have a windows application with a tabcontrol. One of the tab of the tabcontrol has a webbrowser control.Now the issue that I am facing is when the focus is inside the webbrowser control, the normal Ctrl+Tab functionality of the tabcontrol is not working.I want the Ctrl+Tab to change the selected tab of tabcontrol even when the focus is inside webbrowser control in selected tab.How to achieve this ?
I have already tries overriding ProcessCmdKey.but it does not get hit when focus is inside webbrowser control.
I also tried registerhotkey method ,it works but it locks the Ctrl+Tab hotkey within my application & system doesn't respond to any other Ctrl+Tab presses outside my application when application is running, which is expected behaviour of registerhotkey.
Here is the code you need:
If WB.ContainsFocus Then
MsgBox("We have focus, disappearing...")
WB.Document.Body.RemoveFocus()
End If
Now, the question is, when to run that code. If you put it in the WebBrowser1_GotFocus event, you'll need to turn it on and off. Turn the code off if the user is interacting with the WB Control, and turn it back on when they are not and when you expect to be experiencing the problem you've mentioned.
Of course, you could add another line to ensure a particular control/tab/panel etc gets focus after you remove focus from the body. Also, here are 3 other SO questions that have answers which may help you, but these will take you in directions different to the direction I've provided, probably due to the fact that the questions are not identical to yours, but are similar enough to be useful (not listed in order of preference).
Prevent WebBrowser control from stealing focus?
Webbrowser steals focus
Focusing WebBrowser control in a C# application
UPDATE:
I just wanted to add, instead of the .Body.RemoveFocus() you could do this:
WB.Document.Body.Parent.RemoveFocus()
Which I prefer, since the .Document object didn't have an explicit .RemoveFocus method on the intellisense I was gettign in VS2012 RC. This is probably referring to the HTML tag (and not the .Document object) and since the html tag is the only parent to the body tag, it makes sense, and there is no "HTML" object directly available in the intellisense under object, since you can get it via other means, so it's just more convenient doing it this way.
Cheers, and let me know if you need more info on anything.