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In my application i have a form designed with 8 Usercontrols (pages), 1 StatusStrip (bottom) and 1 ToolStrip (top).
The application works like this: i press a button to switch usercontrols, that work as pages, so, i go from menu login_page to menu_page
and from there to any other page.
I manage all this with the help of a visibility method delegate.
Login_page load is different from all, only because ToolStrip is not visible, in any other "page" load both ToolStrip
and StatusStrip are visible.
(i do that because in login_page i manage logins, so only after login i allow ToolStrip controls to the user!!!, so, before login the toolstrip is not visible)
So whats wrong? nothing. When i open the project in c# (not run it) i get the message bellow inside the form, but
when i run it everthing works sweet, 100% like i want.
<System.NullReferenceException: Object reference not set to an instance o an object.
at
Use_Usercontrols_as_Pages.Usercontrol_PageMenu.Usercontrol_PageMenu_VisibleChanged
(object sender, eventargs e) in ...UserControls_as_pages|use_usercontrols_as_Pages\Usercontrol_PageMenu.cs:line 56
at system.windows.forms.controls.onvisiblechanged(eventargs e)
at system.windows.forms.scrollablecontrol.onvisiblechanged(eventargs e)
at system.windows.forms.control.onparentvisiblechanged(eventargs e)
at system.windows.forms.scrollablecontrol.onvisiblechanged(eventargs e)
at system.windows.forms.form..onvisiblechanged(eventargs e)
at system.windows.forms.control.wmshowwindow(message&m)
at system.windows.forms.scrollablecontrol.wndproc(message&m)
at system.windows.forms.containercontrol.wndproc(message&m)
at system.windows.forms.form.wndproc(message&m)
at system.windows.forms.form.wndproc(message&m)
at system.windows.forms.control.controlnativewndow.onmessage(message&m)>
nelsonpaixao@yahoo.com.br
trying to help & get help
modified on Thursday, November 20, 2008 7:35 PM
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When I was an MVP, I reported this as a bug. MS thinks it's a feature, but in fact, it's one of the stupidest changes they've ever made. The IDE runs some, but not all, of your code, and if your code doesn't work when only part of it is run, it won't show in the designer. If you attach one instance of the IDE to another, then you can use the IDE to 'debug' your code. Of course, your code is not broken, the IDE is. You will need to rework your code if you want to use the designer. Which is the stupidest thing ever.
Christian Graus
Driven to the arms of OSX by Vista.
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hi, thanks for the post. 
this application is meent to be my first article submition to codeproject you know? but i really dont know what to make of this, like i said everthing works!!!
i think is not nice to submit a article with that kind of ..."error" or what ever it is
i really dont know that IDE stuff you know?! where can "find" it to change?
nelsonpaixao@yahoo.com.br
trying to help & get help
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Like I said, attach one IDE to another, then try to view the control in the designer, your attached IDE will catch the 'exception' and show you where an object in your code is in a bad state, because not all of your code was run by the IDE.
Christian Graus
Driven to the arms of OSX by Vista.
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Hi,
as the exception indicates, have a look at line 56 of file Usercontrol_PageMenu.cs
chances are adding a null test will fix things.
BTW: make sure your IDE always shows line numbers, that will make things a lot easier:
Compiler errors and run-time exceptions tend to show line numbers
(look at Exception.ToString(), not Exception.Message).
The Visual Studio editor can show them too, but for some mysterious reason does not
do so by default; see menu Tools/Options/Text Editor/All Languages/General/...
If you turn them on, you'll locate problem spots much more easily.
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crap, i going to figure it out some how 
nelsonpaixao@yahoo.com.br
trying to help & get help
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Can some one give me a link which has good demo on how to use the code generated by SQLMetal
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hi i have a dataset which consists of one tables. i need to filter this data set and store it in another table. how can i do this?
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A dataset allows you to set a filter. Then I'm not sure if there's a quicker way than just to iterate over the records and store them.
Christian Graus
Driven to the arms of OSX by Vista.
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Hi ..
There is a quicker way ... use the Select Method of the DataTable
ds.Tables[0].Select(filterExpression); ... read this MSDN article regarding the Select method ... it will help you ...
http://msdn.microsoft.com/en-us/library/det4aw50.aspx[^]
Hope this helps ...
Sincerely Samer Abu Rabie
Note: Please remember to rate this post to help others whom reading it.
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Use a dataview to do the filtering and you can copy the filtered dataview to a new table (dvData.CopyTable I think)
Never underestimate the power of human stupidity
RAH
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hi evryone
i have big problem using com1
i have 9 pin cable (rs232)
i need to light LED from rs232
i try to wright:
port.Write(new byte[] { 0x1B, 0x4C, 0x30, 0x1B, 0x1A }, 0, 5);
but the LED not light
how can i know what to send to recive signal that light the LED,
and what pin's i need to connect to the LED
thank's alot for any help
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Try network byte order?
Need software developed? Offering C# development all over the United States, ERL GLOBAL, Inc is the only call you will have to make.
Happiness in intelligent people is the rarest thing I know. -- Ernest Hemingway
Most of this sig is for Google, not ego.
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what ??  
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still no answer
any one ??....
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Hi,
you failed to sufficiently explain the problem:
- how is the LED connected to the PC? is it attached to a microcontroller of some kind?
if so, which one, what is the command set of the interface?
if not, I must assume it is connected straight to one of the RS232C control pins, so which one, and why would you need to send data bytes then? 5 bytes sent at an unknown baud rate take a few milliseconds at most, so if the LED is connected to the RS232C TxD pin, it gets energy for that long, and the human eye will not notice it al all.
- you did include a series resistor I hope, otherwise the LED has been killed already.
- how does this relate to C#?
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Can/would somebody tell me how to display an icon on a form in C# please (Windows CE 5.0)? I have to display the battery level of a remote sensor on a form. I created several icons, with VS, and depending on its battery level I will pick the corresponding icon file. I'm new to C# and Windows CE 5.0 and I'm sure it’s easy to do but I'm not having any luck with the searches.
Thanks,
Bob
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Which wire did you cut at last? 
Life is 5: 3 me, 1 you.
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hi to all.
i have a html file that contains a "select" control (dropdown) with a few "option"s i need to read the option and the value of each of them,
is it possible to load a html code into a HtmlDocument and then read the control by getElemementByName?
Or does any one have the regex pattern to read the options and values of a dropdown control?
Thanks
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Eli Nurman wrote: is it possible to load a html code into a HtmlDocument and then read the control by getElemementByName?
Yes. However if it is XHTML it would be simpler to use an XML Parser
led mike
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how is that possible to to?
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Eli Nurman wrote: how is that possible to to?
Not sure what they call it on the planet you come from, but round here we call it programming. 
led mike
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Try Html Agility Pack:
http://www.codeplex.com/htmlagilitypack[^]
For a one-off it may be overkill, but if you're going to be doing alot of html parsing it can be incredibly useful to use xpath on html.
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