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• Bi-directional view model syncing with "live" collections and properties (MVVM)

  - by Schneider

  I am getting my knickers in a twist recently about View Models (VM). Just like this guy I have come to the conclusion that the collections I need to expose on my VM typically contain a different type to the collections exposed on my business objects. Hence there must be a bi-directional mapping or transformation between these two types. (Just to complicate things, on my project this data is "Live" such that as soon as you change a property it gets transmitted to other computers) I can just about cope with that concept, using a framework like Truss, although I suspect there will be a nasty surprise somewhere within. Not only must objects be transformed but a synchronization between these two collections is required. (Just to complicate things I can think of cases where the VM collection might be a subset or union of business object collections, not simply a 1:1 synchronization). I can see how to do a one-way "live" sync, using a replicating ObservableCollection or something like CLINQ. The problem then becomes: What is the best way to create/delete items? Bi-directinal sync does not seem to be on the cards - I have found no such examples, and the only class that supports anything remotely like that is the ListCollectionView. Would bi-directional sync even be a sensible way to add back into the business object collection? All the samples I have seen never seem to tackle anything this "complex". So my question is: How do you solve this? Is there some technique to update the model collections from the VM? What is the best general approach to this?

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• How to update a custom dependency property when the datasource list changes

  - by John

  Hi We have a user control with a custom dependency property (DP). The DP is bound to an ObservableCollection. When a new item is added to the collection programatically, the databinding does not update the target DP. Why? We think it's because, unfortunately, in our case the target is not a ListBox or ListView, but a Canvas. The DP, when changed or initialized, is supposed to draw a Shape (!) onto the Canvas, and the shape's position and size is bound to the collection item's two properties: WIDTH, LEFT. Ideally we don't want to clear the Canvas and redraw all items just becasue one has been added (or deleted). But how? So: How can the custom DP take care of drawing the shape for the new collection item? What callback do we need, at what point in time does this have to happen, and what specific MetaDataOptions might there? Also, are there any good resources out there concerning all these dependency property options. They are quite confusing. MSDN does not really help with what we're trying to do. Thanks!

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• Windows Phone app: Binding data in a UserControl which is contained in a ListBox

  - by Alexandros Dafkos

  I have an "AddressListBox" ListBox that contains "AddressDetails" UserControl items, as shown in the .xaml file extract below. The Addresses collection is defined as ObservableCollection< Address Addresses and Street, Number, PostCode, City are properties of the Address class. The binding fails, when I use the "{Binding property}" syntax shown below. The binding succeeds, when I use the "dummy" strings in the commented-out code. I have also tried "{Binding Path=property}" syntax without success. Can you suggest what syntax I should use for binding the data in the user controls? <ListBox x:Name="AddressListBox" DataContext="{StaticResource dataSettings}" ItemsSource="{Binding Path=Addresses, Mode=TwoWay}"> <ListBox.ItemTemplate> <DataTemplate> <!-- <usercontrols:AddressDetails AddressRoad="dummy" AddressNumber="dummy2" AddressPostCode="dummy3" AddressCity="dummy4"> </usercontrols:AddressDetails> --> <usercontrols:AddressDetails AddressRoad="{Binding Street}" AddressNumber="{Binding Number}" AddressPostCode="{Binding PostCode}" AddressCity="{Binding City}"> </usercontrols:AddressDetails> </DataTemplate> </ListBox.ItemTemplate> </ListBox>

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• How do I ensure only the headers are shown for the first item in an ItemsControl in WPF?

  - by Dan Ryan

  I am using MVVM binding an ObservableCollection of children to an ItemsControl. The ItemsControl contains a UserControl used to style the UI for the children. <ItemsControl ItemsSource="{Binding Documents}"> <ItemsControl.ItemTemplate> <DataTemplate> <View:DocumentView Margin="0, 10, 0, 0" /> </DataTemplate> </ItemsControl.ItemTemplate> </ItemsControl> I want to show a header row for the contents of the ItemsControl but only want to show this once at the top (not for every child). How can I implement this behaviour in the DocumentView user control? Fyi I am using a Grid layout to style the child rows: <Grid> <Grid.ColumnDefinitions> <ColumnDefinition Width="34"/> <ColumnDefinition Width="100"/> <ColumnDefinition Width="*" /> <ColumnDefinition Width="60" /> </Grid.ColumnDefinitions> <Grid.RowDefinitions> <RowDefinition /> <RowDefinition /> </Grid.RowDefinitions> <TextBlock Grid.ColumnSpan="4" Grid.Row="0" Text="Should only show this at the top"></TextBlock> <Image Grid.Column="0" Grid.Row="1" Height="24" Width="24" Source="/Beazley.Documents.Presentation;component/Icons/error.png"></Image> <ComboBox Grid.Column="1" Grid.Row="1" Name="ContentTypes" ItemsSource="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type View:MainView}}, Path=DataContext.ContentTypes}" SelectedValue="{Binding ContentType}"/> <TextBox Grid.Column="2" Grid.Row="1" Text="{Binding Path=FileName}"/> <Button Grid.Column="3" Grid.Row="1" Command="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type View:MainView}}, Path=DataContext.RemoveFile}" CommandParameter="{Binding}">Remove</Button> </Grid>

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• WPF: How can I KEEP the same ItemTemplate instance once its created ??

  - by Samir Sabri

  Hello, Here is a cinario: I have a ListView, with ItemsSource = ProjectModel.Instance.PagesModelsCollection; where PagesModelsCollection is an ObservableCollection In the ListView XAML part: <ListView.ItemTemplate> <DataTemplate x:Name="PagesViewDataTemplate"> <DataTemplate.Resources> <Style x:Key="PageHostStyle" TargetType="{x:Type p:KPage}"> </Style> </DataTemplate.Resources> <StackPanel x:Name="MarginStack" Margin="50,50,50,50" > <p:KPage x:Name="PageHost" > </p:KPage> </StackPanel> </DataTemplate> </ListView.ItemTemplate> The problem is the ITemTemplate is re-created each time we refresh the Items. So, if we have 100 Item in the list view, another 100 new ItemTemplate instance will be created if we refresh the items! As a result, if we add UIElements on one of the ItemTemplate intances, those added UIElements will be lost, because the old ITemTemplate is replaced with a new one! How can I KEEP the ItemTemplate instance once its created ??

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• How can I change the VisualState in a View from the ViewModel?

  - by Decker

  I'm new to WPF and MVVM. I think this is a simple question. My ViewModel is performing an asynch call to obtain data for a DataGrid which is bound to an ObservableCollection in the ViewModel. When the data is loaded, I set the proper ViewModel property and the DataGrid displays the data with no problem. However, I want to introduce a visual cue for the user that the data is loading. So, using Blend, I added this to my markup: <VisualStateManager.VisualStateGroups> <VisualStateGroup x:Name="LoadingStateGroup"> <VisualState x:Name="HistoryLoading"> <Storyboard> <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.Visibility)" Storyboard.TargetName="HistoryGrid"> <DiscreteObjectKeyFrame KeyTime="0" Value="{x:Static Visibility.Hidden}"/> </ObjectAnimationUsingKeyFrames> </Storyboard> </VisualState> <VisualState x:Name="HistoryLoaded"> <Storyboard> <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.Visibility)" Storyboard.TargetName="WorkingStackPanel"> <DiscreteObjectKeyFrame KeyTime="0" Value="{x:Static Visibility.Hidden}"/> </ObjectAnimationUsingKeyFrames> </Storyboard> </VisualState> </VisualStateGroup> </VisualStateManager.VisualStateGroups> I think I know how to change the state in my code-behind (something similar to this): VisualStateManager.GoToElementState(LayoutRoot, "HistoryLoaded", true); However, the place where I want to do this is in the I/O completion method of my ViewModel which does not have a reference to it's corresponding View. How would I accomplish this using the MVVM pattern?

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• WPF - How to stop an ItemsControl psuedo-grid's columns from dancing/jumping around during layout

  - by Drew Noakes

  Several other questions on SO have come to the same conclusion I have -- using an ItemsControl with a DataTemplate for each item constructed to position items such that they resemble a grid is much simpler (especially to format) than using a ListView. The code resembles: <StackPanel Grid.IsSharedSizeScope="True"> <!-- Header --> <Grid> <Grid.ColumnDefinitions> <ColumnDefinition Width="Auto" SharedSizeGroup="Column1" /> <ColumnDefinition Width="Auto" SharedSizeGroup="Column2" /> </Grid.ColumnDefinitions> <TextBlock Grid.Column="0" Text="Column Header 1" /> <TextBlock Grid.Column="1" Text="Column Header 2" /> </Grid> <!-- Items --> <ItemsControl ItemsSource="{Binding Path=Values, Mode=OneWay}"> <ItemsControl.ItemTemplate> <DataTemplate> <Grid> <Grid.ColumnDefinitions> <ColumnDefinition Width="Auto" SharedSizeGroup="Column1" /> <ColumnDefinition Width="Auto" SharedSizeGroup="Column2" /> </Grid.ColumnDefinitions> <TextBlock Grid.Column="0" Text="{Binding ColumnProperty1}" /> <TextBlock Grid.Column="1" Text="{Binding ColumnProperty2}" /> </Grid> </DataTemplate> </ItemsControl.ItemTemplate> </ItemsControl> </StackPanel> The problem I'm seeing is that whenever I swap the object to which the ItemsSource is bound (it's an ObservableCollection that I replace the reference to, rather than clear and re-add), the entire 'grid' dances about for a few seconds. Presumably it is making a few layout passes to get all the Auto-width columns to match up. This is very distracting for my users and I'd like to get it sorted out. Has anyone else seen this?

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• MVVM: where is the best place to integrate an id counter, in ViewModel or Repository or... ?

  - by msfanboy

  Hello, I am using http://loungerepo.codeplex.com/ this library needs a unique id when I persist my entities to the repository. I decided for integer not Guid. The question is now where do I retrieve a new integer and how do I do it? This is my current approach in the SchoolclassAdministrationViewModel.cs: public SchoolclassAdministrationViewModel() { _schoolclassRepo = new SchoolclassRepository(); _pupilRepo = new PupilRepository(); _subjectRepo = new SubjectRepository(); _currentSchoolclass = new SchoolclassModel(); _currentPupil = new PupilModel(); _currentSubject = new SubjectModel(); ... } private void AddSchoolclass() { // get the last free id for a schoolclass entity _currentSchoolclass.SchoolclassID = _schoolclassRepo.LastID; // add the new schoolclass entity to the repository _schoolclassRepo.Add(SchoolclassModel.SchoolclassModelToSchoolclass(_currentSchoolclass)); // add the new schoolclass entity to the ObservableCollection bound to the View Schoolclasses.Add(_currentSchoolclass); // Create a new schoolclass entity and the bound UI controls content gets cleaned CurrentSchoolclass = new SchoolclassModel(); } public class SchoolclassRepository : IRepository<Schoolclass> { private int _lastID; public SchoolclassRepository() { _lastID = FetchLastId(); } public void Add(Schoolclass entity) { //repo.Store(entity); } private int FetchLastId() { return // repo.GetIDOfLastEntryAndDoInc++ } public int LastID { get { return _lastID; } } } Explanation: Every time the user switches to the SchoolclassAdministrationViewModel which is datatemplated with a UserControl the saVM Ctor is called and the schoolclass repository is created wherein the FetchLastId() is called and I am up to date with the last ID doing a inc++ on it to get the free one... Do you have any better ideas? What I do not like about my current apporach: -Having a private method in repositry class because a repositry is to fetch data only not "entity logic" like the counter - Having to access from the ViewModel a public property - located in the repository -, actually its not the ViewModel concern to get a entity id and assign it. Actually the ViewModel should ask for a schoolclass POCO and get a SchoolclassModel to bind to the UI. But then I have again to re-read the Schoolclass properties into the SchoolclassModel properties what I want to avoid.

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• Silverlight - C# and LINQ - Ordering By Multiple Fields

  - by user70192

  Hello, I have an ObservableCollection of Task objects. Each Task has the following properties: AssignedTo Category Title AssignedDate I'm giving the user an interface to select which of these fields they was to sort by. In some cases, a user may want to sort by up to three of these properties. How do I dynamically build a LINQ statement that will allow me to sort by the selected fields in either ascending or descending order? Currently, I'm trying the following, but it appears to only sort by the last sort applied: var sortedTasks = from task in tasks select task; if (userWantsToSortByAssignedTo == true) { if (sortByAssignedToDescending == true) sortedTasks = sortedTasks.OrderByDescending(t => t.AssignedTo); else sortedTasks = sortedTasks.OrderBy(t => t.AssignedTo); } if (userWantsToSortByCategory == true) { if (sortByCategoryDescending == true) sortedTasks = sortedTasks.OrderByDescending(t => t.Category); else sortedTasks = sortedTasks.OrderBy(t => t.Category); } Is there an elegant way to dynamicaly append order clauses to a LINQ statement?

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• Silverlight 4 ComboBox - Binding to Nullable data (tried TargetNullValue but not working as expected)

  - by Laurence

  (Please note - I am a Silverlight beginner and am looking for the simplest solution here, e.g. that doesn't involve writing/installing a replacement for the ComboBox control!) This is an issue with a Silverlight 4 application that uses the View Model (MVVM) approach. I have a simple form for editing a "Product" object. Product has a CategoryID property which is nullable (int?). A ComboBox is used to view and set the CategoryID - this is bound to an ObservableCollection of Categories. Product also has number of non-nullable properties bound to TextBoxes. I want the user to see "N/A" in the ComboBox for a product with no category, and to be use this "N/A" option to set CategoryID to null. So, I manually added a Category object with CategoryID=0 and CategoryName="N/A" to the collection; then I set TargetNullValue=0 in the SelectedValue Binding of the ComboBox. My thinking was - when the ComboBox SelectedValue was bound to a null CategoryID it would substitute zero, and therefore select the "N/A" option. When editing a Product with a non-null CategoryID, everything works. However when a null CategoryID is found, two problems occur: No option is selected in the ComboBox (its blank) The ComboBox binding seems broken from this point onwards - any Product I subsequently edit (incl. ones with a non-null CategoryID) have nothing selected in the ComboBox (its still populated with all categories - just no selected item). I've seen reports of problem #2 (here, here) but I was under the impression that #1 should have worked. What am I missing to get the "N/A" option to be selected? XAML for ComboBox: <ComboBox x:Name="cboCategory" ItemsSource="{Binding colCategories, Mode=OneWay}" SelectedValuePath="CategoryID" DisplayMemberPath="CategoryName" SelectedValue="{Binding CurrentProduct.CategoryID, Mode=TwoWay, TargetNullValue=0}" Height="24" Width="344"></ComboBox>

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• Cant insert a object into a silverlight databound combo box

  - by Steve

  Hi Until recently I had a combo box that was bound to a Linq queried IEnumerable of a DataService.Obj type in the bind method, and all worked fine private IEnumerable<DataService.Obj> _GeneralList; private IEnumerable<DataService.Obj> _QueriedList; private void Bind() { _GeneralList = SharedLists.GeneralList; _QueriedList = _GeneralList.Where(q =>q.ID >1000); cmbobox.ItemsSource = _QueriedList; } Then I had to change the method to insert a new obj and set that object as the default obj and now I get a "System.NullReferenceException: Object reference not set to an instance of an object" exception. I know this has to do with inserting into a linq queried ienumerable but I cant fix it. Any help will be gratefully received. private IEnumerable<DataService.Obj> _GeneralList; private IEnumerable<DataService.Obj> _QueriedList; private void Bind() { _GeneralList = SharedLists.GeneralList; _QueriedList = _GeneralList.Where(q =>q.ID >1000); cmbobox.ItemsSource = _QueriedList; DataService.Obj info = new DataService.Obj(); info.ID = "0"; (cmbobox.ItemsSource as ObservableCollection<DataService.Obj>).Insert(0,info); cmbobox.SelectedIndex = 0; } Thanks in advance

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• Access property of DataContext in ItemTemplate

  - by amrinder

  My datacontext has two properties: Items which is a collection and DetailsVisiblity which is enum of type Visiblity. On the page I have a Listbox with ItemsSource="{Binding Entries}". Inside the DataTemplate, I can bind stuff to properties of Items, but how do I get access to DetailsVisiblity which is a property of DataContext? DataContext has two properties: ObservableCollection<Item> Entries, and Visibility DetailsVisiblity. Item class has two properties: Title and Details. Here is the view. How do I bind Visiblity of the second TextBlock to DetailsVisiblity property? <ListBox "{Binding Items}"> <ListBox.ItemTemplate> <DataTemplate> <StackPanel> <TextBlock Text="{Binding Title}" /> <TextBlock Text="{Binding Details}" Visibility="{Binding ???}" /> </StackPanel> </DataTemplate> </ListBox.ItemTemplate> </ListBox>

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• MVVM and Databinding with UniformGrid

  - by JP

  I'm trying to style the back of a WPF chart with some rectangles. I'm using MVVM, and I need the rectangles to be uniformly sized. When defined via Xaml, this works with a fixed "BucketCount" of 4: <VisualBrush> <VisualBrush.Visual> <UniformGrid Height="500" Width="500" Rows="1" Columns="{Binding BucketCount}"> <Rectangle Grid.Row="0" Grid.Column="0" Fill="#22ADD8E6" /> <Rectangle Grid.Row="0" Grid.Column="1" Fill="#22D3D3D3"/> <Rectangle Grid.Row="0" Grid.Column="2" Fill="#22ADD8E6"/> <Rectangle Grid.Row="0" Grid.Column="3" Fill="#22D3D3D3"/> </UniformGrid> </VisualBrush.Visual> <VisualBrush> How can I bind my ObservableCollection of Rectangles? There is no "ItemsSource" property on UniformGrid. Do I need to use an ItemsControl? If so, how can I do this? Thanks in advance.

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• Automapping Collections

  - by vaibhav

  I am using Automapper for mapping my domain model and DTO. When I map Mapper.Map<SiteDTO, SiteEntity> it works fine. But when I use collections of the same entities, it doesn't map. Mapper.Map<Collection<SiteEntity>, Collection<SiteDTO>>(siteEntityCollection); AS per Automapper Wiki, it says the lists implementing ICollection would be mapped, I am using Collection that implements ICollection, but automapper doesn't map it. Am I doing something wrong. public class SiteEntity //SiteDTO has exactly the same properties, so I am not posting it here. { public int SiteID { get; set; } public string Code { get; set; } public string Name { get; set; } public byte Status { get; set; } public int ModifiedBy { get; set; } public DateTime ModifiedDate{ get; set; } public long TimeStamp{ get; set; } public string Description{ get; set; } public string Notes{ get; set; } public ObservableCollection<AreaEntity> Areas{ get; set; } }

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• Bing Maps - Auto update location binding of pushpins

  - by abp

  Hi I'm using the Bing Maps control to display a series of custom pushpins, representing objects which are constantly moving around and changing state. Using databinding the various properties for the objects are being updated as they should, but for some reason this doesn't apply to their locations. I have the map bound to an ObservableCollection as such: <UserControl.Resources> <DataTemplate x:Key="PushpinTemplate"> <v:CustomPushpin /> </DataTemplate> </UserControl.Resources> ... <m:Map Name="map"> <m:MapItemsControl ItemTemplate="{StaticResource PushpinTemplate}" ItemsSource="{Binding Objects}" /> </m:Map> ...and in CustomPushpin: <UserControl ... m:MapLayer.Position="{Binding Location}" m:MapLayer.PositionOrigin="BottomCenter" mc:Ignorable="d" d:DesignHeight="126" d:DesignWidth="85"> Like all other properties, the Location of the individual objects are implemented using INotifyPropertyChanged. private Location _location; public Location Location { get { return _location; } set { _location = value; OnPropertyChanged("Location"); } } When the map is moving, either because of panning or zooming, the objects move, but othersize not. I can't quite figure if I'm doing something wrong here, or if it's a problem with the Bing Maps control. Any thought?

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• how to sort the items in listbox alphabetically?

  - by user2745378

  i need to sort the items alphabetically in listbox when sort button is clicked. (I have sort button in appbar). But I dunno how to achieve this. here is XAML. All help will be much appreciated. <phone:PhoneApplicationPage.Resources> <DataTemplate x:Key="ProjectTemplate"> <Grid> <Grid.ColumnDefinitions> <ColumnDefinition Width="400" /> </Grid.ColumnDefinitions> <TextBlock Grid.Column="1" Text="{Binding Name}" Style="{StaticResource PhoneTextLargeStyle}" /> </Grid> </DataTemplate> </phone:PhoneApplicationPage.Resources> <Grid x:Name="ContentPanel" Grid.Row="1" Margin="0,0,12,0"> <ListBox x:Name="projectList" ItemsSource="{Binding Items}" SelectionChanged="ListBox_SelectionChanged" ItemTemplate="{StaticResource ProjectTemplate}" /> </Grid> Here's my ViewModel namespace PhoneApp.ViewModels { public class ProjectsViewModel: ItemsViewModelBase<Project> { public ProjectsViewModel(TaskDataContext taskDB) : base(taskDB) { } public override void LoadData() { base.LoadData(); var projectsInDB = _taskDB.Projects.ToList(); Items = new ObservableCollection<Project>(projectsInDB); } public override void AddItem(Project item) { _taskDB.Projects.InsertOnSubmit(item); _taskDB.SubmitChanges(); Items.Add(item); } public override void RemoveItem(int id) { var projects = from p in Items where p.Id == id select p; var item = projects.FirstOrDefault(); if (item != null) { var tasks = (from t in App.TasksViewModel.Items where t.ProjectId == item.Id select t).ToList(); foreach (var task in tasks) App.TasksViewModel.RemoveItem(task.Id); Items.Remove(item); _taskDB.Projects.DeleteOnSubmit(item); _taskDB.SubmitChanges(); } } } } I have added the ViewModel C# Code herewith

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• Why the databinding fails in ListView (WPF) ?

  - by Ashish Ashu

  I have a ListView of which ItemSource is set to my Custom Collection. I have defined a GridView CellTemplate that contains a combo box as below : <ListView MaxWidth="850" Grid.Row="1" SelectedItem="{Binding Path = SelectedCondition}" ItemsSource="{Binding Path = Conditions}" FontWeight="Normal" FontSize="11" Name="listview"> <ListView.View> <GridView> <GridViewColumn Width="175" Header="Type"> <GridViewColumn.CellTemplate> <DataTemplate> <ComboBox Style="{x:Null}" x:Name="TypeCmbox" Height="Auto" Width="150" SelectedValuePath="Key" DisplayMemberPath="Value" SelectedItem="{Binding Path = MyType}" ItemsSource="{Binding Path = MyTypes}" HorizontalAlignment="Center" /> </DataTemplate> </GridViewColumn.CellTemplate> </GridViewColumn> </ListView> My Custom collection is the ObservableCollection. I have a two buttons - Move Up and Move Down on top of the listview control . When user clicks on the Move Up or Move Down button I call MoveUp and MoveDown methods of Observable Collection. But when I Move Up and Move Down the rows then the Selected Index of a combo box is -1. I have ensured that selectedItem is not equal to null when performing Move Up and Move Down commands. Please Help!!

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• Bind to a collection's view and just call ToString() in WPF

  - by womp

  I'm binding a GridView to a collection of objects that look like this: public class Transaction { public string PersonName { get; set; } public DateTime TransactionDate { get; set; } public MoneyCollection TransactedMoney { get; set;} } MoneyCollection simply inherits from ObservableCollection<T>, and is a collection of MyMoney type object. In my GridView, I just want to bind a column to the MoneyCollection's ToString() method. However, binding it directly to the TransactedMoney property makes every entry display the text "(Collection)", and the ToString() method is never called. Note that I do not want to bind to the items in MoneyCollection, I want to bind directly to the property itself and just call ToString() on it. I understand that it is binding to the collection's default view. So my question is - how can I make it bind to the collection in such a way that it calls the ToString() method on it? This is my first WPF project, so I know this might be a bit noobish, but pointers would be very welcome.

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• WPF: issue updating UI from background thread

  - by Ted Shaffer

  My code launches a background thread. The background thread makes changes and wants the UI in the main thread to update. The code that launches the thread then waits looks something like: Thread fThread = new Thread(new ThreadStart(PerformSync)); fThread.IsBackground = true; fThread.Start(); fThread.Join(); MessageBox.Show("Synchronization complete"); When the background wants to update the UI, it sets a StatusMessage and calls the code below: static StatusMessage _statusMessage; public delegate void AddStatusDelegate(); private void AddStatus() { AddStatusDelegate methodForUIThread = delegate { _statusMessageList.Add(_statusMessage); }; this.Dispatcher.BeginInvoke(methodForUIThread, System.Windows.Threading.DispatcherPriority.Send); } _statusMessageList is an ObservableCollection that is the source for a ListBox. The AddStatus method is called but the code on the main thread never executes - that is, _statusMessage is not added to _statusMessageList while the thread is executing. However, once it is complete (fThread.Join() returns), all the stacked up calls on the main thread are executed. But, if I display a message box between the calls to fThread.Start() and fThread.Join(), then the status messages are updated properly. What do I need to change so that the code in the main thread executes (UI updates) while waiting for the thread to terminate? Thanks.

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• C# generics with MVVM, pulling the T out of <T>

  - by bufferz

  My Model is a generic class that contains a (for example) Value property which can be int, float, string, bool, etc. So naturally this class is represented something like Model<T>. For the sake of collections Model<T> implements the interface IModel, although IModel is itself empty of any content. My ViewModel contains and instance of Model<T> and it is passed in through ViewModel's constructor. I still want to know what T is in ViewModel, so when I expose Model to the View I know the datatype of Model's buried Value property. The class for ViewModel ends up looking like the following: class ViewModel<T> { private Model<T> _model; public ViewModel(Model<T> model) { ....blah.... } public T ModelsValue {get; set; } } This works fine, but is limited. So now I need to expose a collection of IModels with varying Ts to my View, so I'm trying to set up an ObservableCollection of new ViewModel<T>s to a changing list of IModels. The problem is, I can't figure out how to get T from Model<T> from IModel to construct ViewModel<T>(Model<T>) at runtime. In the VS2010 debugger I can mouseover any IModel object and see its full Model<int> for example at runtime so I know the data is in there. Any ideas?

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• Firing PropertyChanged event in a complex, nested type in WPF

  - by John

  Hey I have a question about the PropertyChanged vent firing in WPF whne it is used in a complex type. I have a class called DataStore and a list of Departments (an ObservableCollection), and each department again has a list of Products. Properties in the Product class that are changed also affect properties in the Department and DataStore class. How does each Product notify the Department it belongs to, and the DataStore (which is the mother class of all) that one or more of its properties have changed their values? Example: a product has a property NumberSoldToday and is bound. The Department has a property called TotalNumberOfProductsSold: public int TotalNumberOfProductsSold { get { int result = 0; foreach(Product p in this.products) result += p.NumberSoldToday; return result; } } And the data store has a property TotalProductsSold (for all departments): public int TotalProductsSold { get { int result = 0; foreach(Product p in this.deparments) result += p.TotalNumberOfProductsSold; return result; } } If all these properties are bound, and the innermost property changes, it must somehow notify that the value of the other 2 changed as well. How? The only way I can see this happening is to hook up the PropertyChanged event in each class. Th event must also fire when deleting, adding to the collection of products and deparments, respectively. Is there a better, more clever way to do this?

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• WCF operationcontract with List type unavailable in (Silverlight) client

  - by Dave

  This is the first time I have tried returning a List of data to a Silverlight client, so I'm having trouble getting the client to recognize this operationcontract. All others are fine. I have a method on the server called ReadOwFileData that needs to return a List. ReadOwFileDataCompletedEventArgs shows up in the Object Browser in the client, but not ReadOwFileDataAsync. What I want is similar to the tutorial here. The Dictionary collection type on the client is set to System.Collections.Generic.List. I tried deleting and recreating the service reference. Web.Config on the server is using basicHttpBinding. Here is the operationcontract on the server: [OperationContract] public List<OwFileData> ReadOwFileData(string OrderID) { DataClasses1DataContext db = new DataClasses1DataContext(); var dFileData = (from p in db.OwFileDatas where p.OrderID == OrderID select p).ToList(); List<OwFileData> x = new List<OwFileData>(dFileData); return x; } Incidently, this works fine: [OperationContract] public Customer GetShippingAndContactInfo(string login, string ordernum) { DataClasses1DataContext db = new DataClasses1DataContext(); Customer dInfo = (from p in db.Customers where p.Login == login select p).Single(); return dInfo; } I would like to read this data in the client and place it into an object I created called ObservableCollection. But that obviously can't happen until the client can see the method on the server. I do not know if this is an acceptable start, but this is what is on the client so far. The ReadOwFileDataAsync object is null: void populatefilesReceivedDataSource(string OrderID) { ArtUpload.ServiceReference1.UploadServiceClient client = new ArtUpload.ServiceReference1.UploadServiceClient(); var myList = client.ReadOwFileDataAsync(OrderID); // can I just itterate thru the list instead of 'binding' }

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• What am I doing wrong with my ItemsControl & databinding?

  - by Joel

  I'm reworking my simple hex editor to practice using what I've recently learned about data binding in WPF. I'm not sure what I'm doing wrong here. As I understand it, for each byte in the collection "backend" (inherits from ObservableCollection), my ItemsControl should apply the DataTemplate under resources. This template is just a textbox with a binding to a value converter. So I'm expecting to see a row of textboxes, each containing a string representation of one byte. When I use this XAML, all I get is a single line of uneditable text, which as far as I can tell doesn't use a textbox. What am I doing wrong? I've pasted my XAML in below, with the irrelevant parts (Menu declaration, schema, etc) removed. <Window ...> <Window.Resources> <local:Backend x:Key="backend" /> <local:ByteConverter x:Key="byteConverter" /> <DataTemplate DataType="byte"> <TextBox Text="{Binding Converter={StaticResource byteConverter}}" /> </DataTemplate> </Window.Resources> <StackPanel> <ItemsControl ItemsSource="{Binding Source={StaticResource backend}}"> <ItemsControl.ItemsPanel> <ItemsPanelTemplate> <WrapPanel /> </ItemsPanelTemplate> </ItemsControl.ItemsPanel> </ItemsControl> </StackPanel> </Window>

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• INotifyPropertyChanged event listener within respective class not firing on client side (silverlight)

  - by Rob

  I'm trying to work out if there's a simple way to internalize the handling of a property change event on a Custom Entity as I need to perform some bubbling of the changes to a child collection within the class when the Background Property is changed via a XAML binding: public class MyClass : INotifyPropertyChanged { [Key] public int MyClassId { get; set; } [DataMember] public ObservableCollection<ChildMyClass> MyChildren { get; set; } public string _backgroundColor; [DataMember] public string BackgroundColor { get { return this._backgroundColor; } set { this._backgroundColor = value; if (this.PropertyChanged != null) { this.PropertyChanged(this, new PropertyChangedEventArgs("BackgroundColor")); } } } public MyClass() { this.BackgroundColor = "#FFFFFFFF"; this.PropertyChanged += MyClass_PropertyChanged; } public event PropertyChangedEventHandler PropertyChanged; void MyClass_PropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e) { //Do something here - fires client side but not server side } } I can listen to the event by externalizing it without any problems but it's an ugly way to handle something that want to set and forget inside my class e.g.: public class SomeOtherClass { public SomeOtherClass() { MyClass mc = new MyClass(); mc.PropertyChanged += MyClass_PropertyChanged; } void MyClass_PropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e) { MyClass mc = (MyClass)sender; mc.UpdateChildren(); } }

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• Silverlight ~ MVVM ~ Dynamic setting of Style property based on model value

  - by eponymous23

  I have a class called Question that represents a question and it's answer. I have an application that renders an ObservableCollection of Question objects. Each Question is rendered as a StackPanel that contains a TextBlock for the question verbiage, and a TextBox for the user to enter in an answer. The questions are rendered using an ItemsControl, and I have initially set the Style of the Questions's StackPanel using a StaticResource key called 'IncorrectQuestion' (defined in UserControl.Resources section of the page). In the UserControl.Resources section, I've also defined a key calld 'CorrectQuestion' which I need to somehow apply to the Question's StackPanel when the user correctly answers the question. My problem is I'm not sure how to dynamically change the Style of the StackPanel, specifically within the constraints of a ViewModel class (i.e. I don't want to put any style selection code in the View's code-behind). My Question class has an IsCorrect property which is accurately being set when the correction is answered. I'd like to somehow reflect the IsCorrect value in the form of a Style selection. How do I do that?

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