Disappearing Data on Dynamically Loaded WPF Form
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From: ryan baldwin on 19 Jun 2008 17:43 Hey all - I'm seeing some extremely odd behaviour on dynamically loaded XAML forms that are bound to an XmlDataProvider. This will be slightly difficult for me to explain, so I'll try to give everybody some background of what we're doing and what the problem is. We're creating an application for our client that has to generate forms, on the fly, that revolve around XSD (which they will be updating with additional complexTypes whenever they need). Pretend you have a whole bunch of XSD complexTypes, and the application has to create forms that allow users to create XML fragments that are valid for each XSD complexType. For example, perhaps they have an XSD ComplexType named "Dog" with a few elements (colour, gender, and breed) - our application will be required to generate a form with colour, gender, and breed input controls. This is easily achieved by running an XSLT stylesheet over the XSD and generating a bunch of XAML at run time, which we then load it into the app using a XamlReader. The generated XAML contains 2 XmlDataProviders which the controls bind to: 1 for binding pick lists (some of the controls are comboboxes), and a second that is the user-created XML fragment. The controls are bound to these XmlDataProviders as one would normally bind to an XmlDAtaProvider in XAML; using XPath. I have a single class that's responsbile for loading the styles sheets, creating the XAML on the fly, and keeping track of the generated XAML's namespace (so that I can reference the various elements on the generated XAML fragment if needed). I have everything binding, rendering, and saving beautifully (although the saving is a bit of a hack due to the XmlDataProvider not creating elements/attributes on the fly)... with one extremely frustrating and puzzling exception. Sometimes, after generating, loading, and binding the XAML form, data on that form will disappear if I modify data on other parts of that same form. For example, lets say I have 3 textboxes, "Manufacturer", "Make", and "Model", where "Make" and "Model" are in a stack panel. I provide a value for Manufacturer, all is well. When I provide the value for Make or Model, however, the value for Manufacturer suddenly disappears. All 3 textboxes are bound against an XmlDataProvider and are TwoWay. Note that if I have multiple textboxes at the same level in the XAML (such as all in a grid, and none of them in a child stackpanel), then they all behave fine. It's only when some of the textboxes are "deeper" in the visual/logical tree, such as in a groupbox or stackpanel, when I witness the behaviour. I have no idea why data is just disappearing like this... it makes no sense to me. None of the three xaml elements are dependent upon eachother - the only thing they have in common is the XmlDataProvider (however all 3 have a different XPath). Also, if I take the generated XAML and create a normal Xaml page in VisualStudio, build and deploy, none of this behaviour is ever exhibited - it seems to only happen when the form is generated and loaded on the fly. Has anybody experienced anything like this? Has anybody observed this behaviour? Have I made any sense? Please help, ask questions, etc - as I'm currently blocked of advancing on anything until I can get this resolved (I've burned a couple days exhausting ideas). Thanks. - ryan.
From: Linda Liu[MSFT] on 19 Jun 2008 23:58 Hi Ryan, Welcome to the MSDN managed Newsgroup! Your problem seems a little complex. It would be better for us to trouble-shoot the problem for you if you could provide a sample project that could just reproduce the problem. Please send your sample project to my email box (v-lliu(a)microsoft.com). Thank you for your understanding and cooperation! I look forward to your reply. Sincerely, Linda Liu Microsoft Online Community Support Delighting our customers is our #1 priority. We welcome your comments and suggestions about how we can improve the support we provide to you. Please feel free to let my manager know what you think of the level of service provided. You can send feedback directly to my manager at: msdnmg(a)microsoft.com. ================================================== Get notification to my posts through email? Please refer to http://msdn.microsoft.com/subscriptions/managednewsgroups/default.aspx#notif ications. Note: The MSDN Managed Newsgroup support offering is for non-urgent issues where an initial response from the community or a Microsoft Support Engineer within 1 business day is acceptable. Please note that each follow up response may take approximately 2 business days as the support professional working with you may need further investigation to reach the most efficient resolution. The offering is not appropriate for situations that require urgent, real-time or phone-based interactions or complex project analysis and dump analysis issues. Issues of this nature are best handled working with a dedicated Microsoft Support Engineer by contacting Microsoft Customer Support Services (CSS) at http://msdn.microsoft.com/subscriptions/support/default.aspx. ================================================== This posting is provided "AS IS" with no warranties, and confers no rights.
From: ryan baldwin on 20 Jun 2008 10:44 Hi Linda, The problem is indeed complex. I'll try my best to create a small sample project that reproduces the error. Thanks. - ryan. Linda Liu[MSFT] wrote: > Hi Ryan, > > Welcome to the MSDN managed Newsgroup! > > Your problem seems a little complex. It would be better for us to > trouble-shoot the problem for you if you could provide a sample project > that could just reproduce the problem. Please send your sample project to > my email box (v-lliu(a)microsoft.com). > > Thank you for your understanding and cooperation! > I look forward to your reply. > > Sincerely, > Linda Liu > Microsoft Online Community Support > > Delighting our customers is our #1 priority. We welcome your comments and > suggestions about how we can improve the support we provide to you. Please > feel free to let my manager know what you think of the level of service > provided. You can send feedback directly to my manager at: > msdnmg(a)microsoft.com. > > ================================================== > Get notification to my posts through email? Please refer to > http://msdn.microsoft.com/subscriptions/managednewsgroups/default.aspx#notif > ications. > > Note: The MSDN Managed Newsgroup support offering is for non-urgent issues > where an initial response from the community or a Microsoft Support > Engineer within 1 business day is acceptable. Please note that each follow > up response may take approximately 2 business days as the support > professional working with you may need further investigation to reach the > most efficient resolution. The offering is not appropriate for situations > that require urgent, real-time or phone-based interactions or complex > project analysis and dump analysis issues. Issues of this nature are best > handled working with a dedicated Microsoft Support Engineer by contacting > Microsoft Customer Support Services (CSS) at > http://msdn.microsoft.com/subscriptions/support/default.aspx. > ================================================== > This posting is provided "AS IS" with no warranties, and confers no rights. >
From: Linda Liu[MSFT] on 24 Jun 2008 22:23
Hi Ryan, How about your sample project now? I know when you're trying to reproduce the problem you encountered another problem and you posted another issue with the title "WPF ComboBox Binding Confusion" in the microsoft.public.dotnet.framework.windowsforms.databinding newsgroup. The issue you described in the "WPF ComboBox Binding Confusion" post is confirmed a limitation of the ComboBox control by our product team. The reason behind this issue is that ComboBox uses a private binding to get the text representing the selected item (see TextSearch.GetPrimaryText). This binding binds directly to the selected item, in this case an XmlElement. There's no back link from the XmlElement to the XmlDataProvider, and therefore no way to get to the namespace map. So any binding that uses ns prefixes won't be able to map them to Uri's. A workaround is to specify Binding.XmlNamespaceManager for the ComboBox explicitly: <ComboBox Binding.XmlNamespaceManager="{StaticResource namespaceMappings}" ../> Hope this will help you to reproduce the original problem in a simple project. I look forward to your reply! Sincerely, Linda Liu Microsoft Online Community Support Delighting our customers is our #1 priority. We welcome your comments and suggestions about how we can improve the support we provide to you. Please feel free to let my manager know what you think of the level of service provided. You can send feedback directly to my manager at: msdnmg(a)microsoft.com. This posting is provided "AS IS" with no warranties, and confers no rights. |