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Hi,
I have a WPF form for the user to edit some details of an object. Most of the fields are fairly simple text/numeric style fields. I've bound the controls to the properties on the object being edited, and everything works great.
Except, how do I cancel the changes when the user hits the cancel button?
Simon
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Simon,
You have some options.
1. You can keep a copy of the object and replace the original values from the copy if the user cancels.
2. If this is a database application, just reread the record from the database. (or reread from the original source)
modified 27-Feb-21 21:01pm.
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Thanks Karl,
I was hoping there was something simpler than that. To be honest, it's easier to just go back to the old style and copy the object to the controls when the form is opened, then from the controls to the object when the user hits OK. I don't get the advantage of data binding. Am I missing something?
Simon
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Yes I think you may be missing a number of built in features.
WPF 3.5 now supports the IDataErrorInfo interface.
There is plenty of info out there on WPF object data binding.
I'm working on an article today that includes a notification control that is wired up to the business object.
I about 2 weeks I'll also have a the 4th in my WPF Business Application series that covers "how to" do a great number of things with the data binding and business objects.
Trust me, you want to try and use the WPF Data Binding. Very powerful.
Bea Costa is the First Lady of WPF Data Binding. Here blog is here: http://www.beacosta.com/blog/[^]
modified 27-Feb-21 21:01pm.
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I'll stick with it. I'm still new to WPF, we're only using it in small internal apps at the moment. Nothing serious.
I actually found something on her blog that helps with my original question http://www.beacosta.com/blog/?p=15[^]. If I set the update source trigger to explicit, and call UpdateSource() when the user hits OK, that looks like it will do what I want. I'll try it out.
I'll keep a watch out for those articles, they sound useful.
Thanks for the help,
Simon
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Simon,
Glad to hear it.
WPF has a learning curve, but it is worth it! 
modified 27-Feb-21 21:01pm.
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Hi guys.
We have a WPF app, it's only use of COM is that we have a control which wraps the native windows media player control, because the WPF one is too slow. It's worked fine for ages, but suddenly, there is an intermittent crash. It never crashes the first time it's run. When it does crash, it's in this method:
try
{
Application.Current.MainWindow.MinHeight = ActualHeight + 100;
}
catch
{
// Empty - will crash if we are not registered
}
which is in the load event for our tab control. At this stage, the app has done all it's heavy lifting and is in fact visible. An error message comes up, and the app closes. If I get it to crash in the debugger, I get this message three times:
DisconnectedContext was detected
Message: Context 0x21a250' is disconnected. Releasing the interfaces from the current context (context 0x21a0e0).This may cause corruption or data loss. To avoid this problem, please ensure that all contexts/apartments stay alive until the applicationis completely done with the RuntimeCallableWrappers that represent COM components that liveinside them.
and this is the exception itself:
Sunday, 17 February 2008
Not enough quota is available to process this command
at MS.Win32.UnsafeNativeMethods.PostMessage(HandleRef hwnd, Int32 msg, IntPtr wparam, IntPtr lparam)
at System.Windows.Interop.HwndTarget.UpdateWindowSettings(Boolean enableRenderTarget, List`1 channelList)
at System.Windows.Interop.HwndTarget.UpdateWindowPos(IntPtr lParam)
at System.Windows.Interop.HwndTarget.HandleMessage(Int32 msg, IntPtr wparam, IntPtr lparam)
at System.Windows.Interop.HwndSource.HwndTargetFilterMessage(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o)
at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Boolean isSingleParameter)
at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Boolean isSingleParameter, Delegate catchHandler)
All the googling I've done on this message indicates it means the system doesn't have enough resources, but all I'm trying to do in the line that crashes it, is set the minimum height of a control !!! In the debugger, all the properties I am trying to read or set are able to be viewed, Application.Current.MainWindow.MinHeight is 0.0, reading it does not create an exception, as I would have expected.
Any help or guidance greatly appreciated.
Christian Graus - Microsoft MVP - C++
"also I don't think "TranslateOneToTwoBillion OneHundredAndFortySevenMillion FourHundredAndEightyThreeThousand SixHundredAndFortySeven()" is a very good choice for a function name" - SpacixOne ( offering help to someone who really needed it ) ( spaces added for the benefit of people running at < 1280x1024 )
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It does looks like some windowing mess related to STAs hence the gut feeling like some re-entrancy problem to me.. But very difficult to say for sure or figure out without having a mini project to repro it.
I would suggest a hack just to see if it gets around it, you know, finding the window and just posting the message to achieve the same effect. Or move the whole thing around with a timer (yet another ugly hack), it is ugly the mess with RCW/CCW/COM objects being or not being disposed of (the error looks like a stub missing, carpet pulled underneath; I believe CoDisconnectObject was the way around those but might be going way off tangent here).
IIRC, it was possible to get apartments (and most likely contexts) IDs too straight from the marshal interface packet stream. Then you'd have to chase all the OXIDs and find the culprit etc etc. Pretty heavy stuff but it is possible to debug the entire show even if it means loading the debug symbols for OS and whatever else..
Just ideas..
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Christian,
Seems like you have two independent issues here. For the purpose of troubleshooting, can you separate the two, to allow us to work the WPF height issue. By that I mean, can you place a button in the tab control, set its size in code and then allow the resize code to run. This is one simple way of separating the two.
Christian Graus wrote: which is in the load event for our tab control.
Is this a custom tab control, or the standard tab control?
Christian Graus wrote: Application.Current.MainWindow.MinHeight = ActualHeight + 100;
What UIElement does ActualHeight point to?
Is the tab control is on the MainWindow or another window?
Christian Graus wrote: It's worked fine for ages, but suddenly, there is an intermittent crash.
Was this after a framework upgrade, Windows Update or media player update?
Do you have a machine that has your older configuration that you can run the code on? Say an older Windows XP box?
Have you thought about setting the Window property ResizeSizeToContent="WidthAndHeight". With the use of Margins, this will give you the additional height you need automatically.
Failing the above, can you send me the project so I can see all the code, XAML and step through it?
modified 27-Feb-21 21:01pm.
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Karl Shifflett wrote: Was this after a framework upgrade, Windows Update or media player update?
No, it was after a code change, and happens on all machines.
Karl Shifflett wrote: Do you have a machine that has your older configuration that you can run the code on? Say an older Windows XP box?
I have the old code base, I intend on doing a diff and working through the changes to see which caused it, although nothing major has changed.
Karl Shifflett wrote: Have you thought about setting the Window property ResizeSizeToContent="WidthAndHeight". With the use of Margins, this will give you the additional height you need automatically.
Thanks - I will look into this.
Karl Shifflett wrote: Failing the above, can you send me the project so I can see all the code, XAML and step through it?
It's a big project, thanks for the offer, I'll take you up on it if I need to.,
Christian Graus - Microsoft MVP - C++
"also I don't think "TranslateOneToTwoBillion OneHundredAndFortySevenMillion FourHundredAndEightyThreeThousand SixHundredAndFortySeven()" is a very good choice for a function name" - SpacixOne ( offering help to someone who really needed it ) ( spaces added for the benefit of people running at < 1280x1024 )
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Sorry to come back to an ancient thread, but did you resolve/locate the cause of this issue?
I am currently experiencing the same MDA error problem and I beleive it is the result of COM interop issues.
Do you have any pointers for me?
Error:
DisconnectedContext was detected
Message: Context 0x2736e8' is disconnected. Releasing the interfaces from the current context (context 0x2737a0).This may cause corruption or data loss. To avoid this problem, please ensure that all contexts/apartments stay alive until the application is completely done with the RuntimeCallableWrappers that represent COM components that live inside them.
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hi,
i am very new to silverlight, can you suggest me any site that will give basic information abt silverlight app, how to run them and usage
thaknx in advance
koolprasad2003 
Be a good listener...Because Opprtunity knoughts softly...N-Joy
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How about this...[^]
Best regards,
Paul.
Jesus Christ is LOVE! Please tell somebody.
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thankx many ...
as you say...
Michael Sync wrote: - Silverlight is web technology so you can run the application on browser.
it is different from asp.Net web aplication 2.0 ????
regards
koolprasad2003
Be a good listener...Because Opprtunity knoughts softly...N-Joy
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koolprasad2003 wrote: it is different from asp.Net web aplication 2.0 ????
There are a lot of differences between ASP.NET and Silverlight.
- Silverlight is like Flash. You will see it as embedded object on the browser. For ASP.NET, it's just normal HTML page.
- ASP.NET is the server-side technology. Silverlight is client-side technology that works on browser.
- You don't need any extra plugin to view the ASP.NET website but you will need Silverlight plugin to view the Silverlight content.
- You will need Microsoft .NET and Windows server to host ASP.NET web site but you don't need anything for Silverlight. You can host the silverlight application on Linux server or any server that you like.
- ASP.NET uses HTML and Silverlight uses XAML.
- You won't get the same view for ASP.NET in different browsers. (If you have some experiences in Ajax-enabled website development, you will know how to fix something for IE6 and other thing for Firefox or other browsers). But with Silverlight, you will get the same view for all browsers.
- and there may be more...
There are only one same thing. Both website can be viewed with browsers.
Hope that you will get some ideas about that.
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Michael Sync wrote: you will need Silverlight plugin to view the Silverlight content.
For Viewing It's fine but what about Interface to develop a Silverlight Powered Application?
Michael Sync wrote: You will see it as embedded object on the browser.
Is it going to be done through a browser? 
Michael Sync wrote: But with Silverlight, you will get the same view for all browsers.
Sounds Gooood  , That is going to save our lots of efforts and time that we spend for all browser compatible application.
Believe Yourself™  ™
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Hello,
Gandalf - The White wrote: what about Interface to develop a Silverlight Powered Application?
I already answered this question in this post[^].
Gandalf - The White wrote: Is it going to be done through a browser?
For development? no. What I was saying is that when Silverlight object is the embedded object...
Gandalf - The White wrote: That is going to save our lots of efforts and time that we spend for all browser compatible application.
Yes. It's really good. but MS need to take some times to make this happen. For the time being, Silverlight works on IE and Firefox on IE and Saferi on Mac. Moonlight will come for Linux users but it might take some time... I think SL will support Opera in next release beta1... but not like Javascript, there are only two options... SL will work or won't work at all. 
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Hey guys,
I've got a client with a 3d desktop application and a 3d ActiveX web browser plugin.
They're asking about Silverlight - instead of an ActiveX control, could their browser plug-in be a Silverlight application? For this to be possible, Silverlight must support their existing 3d engine (a COM object) - is this possible? Can I write a Silverlight application that uses a 3rd party COM object to do 3d rendering?
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Judah Himango wrote: is this possible? Can I write a Silverlight application that uses a 3rd party COM object to do 3d rendering?
No.
but Silverlight beta will have build-in 3D support.. And it will be released around March. (maybe, with MIX08)
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Interesting, thanks for the answer. I had heard several months back that Silverlight would not have WPF's 3d support. This has changed?
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Judah Himango wrote: Interesting, thanks for the answer. I had heard several months back that Silverlight would not have WPF's 3d support. This has changed?
Initially, I also heard that 3D won't be supported in Silverlight in order to make SL "cross-browsers". but I read it somewhere mentioned that we may get 3D with a few limitations in Silverlight since a lot of people request this feature... As I'm not from UX team, I can't say about this for sure. but for the time being, Silverlight need to have a lot of things (data-binding, controls, layout and etc) so 3D won't be on high priority.
I think we might heard something about this in MIX08..
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I am working in the latest preview of blend 2 and i am getting an error that i can't seem to figure out. I have a data template for a gridview column and i am the following error:
Mapping URI 'clr-namespace:Ups_Trak_System;assembly=Ups Trak System' is not valid.
However, in visual studio it compiles fine w/o any errors.
When i take out the Foreground attribute the error goes away so i'm thinking that it somehow can't find the "BrushConverter". Could someone please take a look at this Image[^] of the markup and see if i am doing it right? i would have just posted the markup but when i previewed it it wouldn't display correctly.
Don't be overcome by evil, but overcome evil with good
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I noticed that you're setting the Path to "*".
Any reason you not setting the Path to a DependencyProperty name?
modified 27-Feb-21 21:01pm.
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