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• What's the order of execution when using IDataErrorInfo?

  - by Benny Jobigan

  Many times with WPF, we use INotifyPropertyChanged and IDataErrorInfo to enable binding and validation on our data objects. I've got a lot of properties that look like this: public SomeObject SomeData { get { return _SomeData; } set { _SomeData = value; OnPropertyChanged("SomeData"); } } Of course, I have an appropriate overridden IDataErrorInfo.this[] in my class to do validation. Question 1) In a binding situation, what happens? For example: User enters new data. Binding writes data to property. Property set method is executed. Binding checks this[] for validation. If the data is invalid, the binding sets the property back to the old value. Property set method is executed again. This is important if you are adding "hooks" into the set method, like: public string PathToFile { get { return _PathToFile; } set { if (_PathToFile != value && // prevent unnecessary actions OnPathToFileChanging(value)) // allow subclasses to do something or stop the setter { _PathToFile = value; OnPathToFileChanged(); // allow subclasses to do something afterwards OnPropertyChanged("PathToFile"); } } }

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• React to change on a static property

  - by Stiggler

  I'm re-writing an MXML item renderer in pure AS. A problem I can't seem to get past is how to have each item renderer react to a change on a static property on the item renderer class. In the MXML version, I have the following binding set up on the item renderer: instanceProperty={callInstanceFunction(ItemRenderer.staticProperty)} What would be the equivalent way of setting this up in AS (using BindingUtils, I assume)? UPDATE: So I thought the following wasn't working, but it appears as if Flex is suppressing errors thrown in the instanceFunction, making it appear as if the binding itself is bad. BindingUtils.bindSetter(instanceFunction, ItemRenderer, "staticProperty"); However, when instanceFunction is called, already initialized variables on the given instance are all null, which was the cause of the errors referenced above. Any ideas why this is?

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• Hot to declare itemTemplate that has Itemsource as Enum Values in WPF?

  - by Ashish Ashu

  I have a enum let's say Enum MyEnum { FirstImage, SecondImage, ThirdImage, FourthImage }; I have binded this Enum to my combobox in XAML. While defining an combobox I have defined an ItemTemplate of combox to take Two UI element: TextBlock that show the enum value (Description) Image I have done this much in XAML. I am wondering where I can specify the Image corrosponding to each item of Enum. Is that possible through data trigger ? I really appreciate if anyone have the XAML for this scenario. Many Thanks in advance

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• Datagridview Winforms Add or Delete Rows in Edit Mode with Collection Binding

  - by user630548

  In my datagridview, I bind a List of objects named 'ProductLine'. But unfortunately with this approach I cannot 'Add' or 'Delete' rows to the datagridview in edit mode. When I create a fresh new order I can Add or Delete rows but once I save it and try to open it in Edit then it doesn't let me 'Add' or 'Delete' (via keyboard). Any idea? Here is the code for this: If it is a fresh Order then I do something like this: private void Save(){ for (int i = 0; i <= dtgProdSer.RowCount - 1; i++) { if ((itemList != null) && (itemList.Count > i)) productLine = itemList[i]; else productLine = new ProductLine(); productLine.Amount = Convert.ToDouble(dataGridViewTextBoxCell.Value); } } And if it is an Edit then in the Form_Load I check ProductId is NON Zero then I do the following: private void fillScreen{ dtgProdSer.DataSource = itemList; } But with this I cannot Add or Delete Rows in Edit mode. Any advise is greatly appreciated.

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• Binding DataTemplates (or another aproach)

  - by Bataglião

  Hi all, I'm having some troubles trying to dynamically generate content in WPF and after it bind data. I have the following scenario: TabControl - Dynamically generated TabItems through DataTemplate - inside TabItems, I have dynamic content generated by DataTemplate that I wish to bind (ListBox). The code follows: ::TabControl <TabControl Height="252" HorizontalAlignment="Left" Name="tabControl1" VerticalAlignment="Top" Width="458" Margin="12,12,12,12" ContentTemplate="{StaticResource tabItemContent}"></TabControl> ::The Template for TabControl to generate TabItems <DataTemplate x:Key="tabItemContent"> <Grid> <Grid.ColumnDefinitions> <ColumnDefinition Width="*" /> </Grid.ColumnDefinitions> <Grid.RowDefinitions> <RowDefinition Height="*" /> </Grid.RowDefinitions> <ListBox ItemTemplate="{StaticResource listBoxContent}" ItemsSource="{Binding}"> </ListBox> </Grid> </DataTemplate> ::The template for ListBox Inside each TabItem <DataTemplate x:Key="listBoxContent"> <Grid> <Grid.ColumnDefinitions> <ColumnDefinition Width="22"/> <ColumnDefinition Width="*" /> </Grid.ColumnDefinitions> <Image Grid.Column="0" Source="{Binding Path=PluginIcon}" /> <TextBlock Grid.Column="1" Text="{Binding Path=Text}" /> </Grid> </DataTemplate> So, when I try to do this on code inside a loop to create the tabitems: TabItem tabitem = tabControl1.Items[catIndex] as TabItem; tabitem.DataContext = plugins.ToList(); where 'plugins' is an Enumerable The ListBox is not bounded. I tried also to find the ListBox inside the TabItem to set the ItemSource property but no success at all. Someone have an idea on how to do that? Thanks in advance.

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• Trouble binding command in grid menu item.

  - by Pete

  I have a grid that's inside a usercontrol derived class called MediatedUserControl. I'm adding a context menu to let the user delete an item, but I've been unable to figure out how to bind the command to my command property. I'm using MVVM and my viewmodel implements a public ICommand property called DeleteSelectedItemCommand. However, when the view is displayed, I get the following message in the output window: System.Windows.Data Error: 4 : Cannot find source for binding with reference 'RelativeSource FindAncestor, AncestorType='BRO.View.MediatedUserControl', AncestorLevel='1''. BindingExpression:Path=DataContext.DeleteSelectedItemCommand; DataItem=null; target element is 'BarButtonItem' (HashCode=6860584); target property is 'Command' (type 'ICommand') I feel like I generally have a good handle on bindings like this and can't figure out what it is I'm missing here. Thanks for any help you can provide. <dxg:GridControl HorizontalAlignment="Left" Margin="12,88,0,0" x:Name="gridControl1" VerticalAlignment="Top" Height="500" Width="517" DataSource="{Binding ItemList}" BorderBrush="{StaticResource {x:Static SystemColors.ActiveBorderBrushKey}}" ShowBorder="True" Background="{StaticResource {x:Static SystemColors.ControlLightBrushKey}}" UseLayoutRounding="False" DataContext="{Binding}"> <dxg:GridControl.Columns> <dxg:GridColumn FieldName="Code" Header="Code" Width="107" /> <dxg:GridColumn FieldName="Name" Header="Item" Width="173" /> <dxg:GridColumn FieldName="PricePerItem" Header="Unit Price" Width="70"> <dxg:GridColumn.EditSettings> <dxe:TextEditSettings DisplayFormat="N2" /> </dxg:GridColumn.EditSettings> </dxg:GridColumn> <dxg:GridColumn FieldName="Quantity" Header="Qty" Width="50" AllowEditing="True" /> <dxg:GridColumn FieldName="TotalPrice" Header="Total Price" Width="90"> <dxg:GridColumn.EditSettings> <dxe:TextEditSettings DisplayFormat="N2" /> </dxg:GridColumn.EditSettings> </dxg:GridColumn> </dxg:GridControl.Columns> <dxg:GridControl.View> <dxg:TableView ShowIndicator="False" ShowGroupPanel="False" MultiSelectMode="Row" AllowColumnFiltering="False" AllowBestFit="False" AllowFilterEditor="False" AllowEditing="False" AllowGrouping="False" AllowSorting="False" AllowResizing="False" AllowMoving="False" AllowMoveColumnToDropArea="False" AllowDateTimeGroupIntervalMenu="False" > <dxg:TableView.RowCellMenuCustomizations> <dxb:BarButtonItem Name="deleteRowItem" Command="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType=view:MediatedUserControl, AncestorLevel=1}, Path=DataContext.DeleteSelectedItemCommand}"> </dxb:BarButtonItem> </dxg:TableView.RowCellMenuCustomizations> </dxg:TableView> </dxg:GridControl.View>

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• bind linq expression

  - by Neir0

  Hi, I have a ListView and ObservableCollection in my wpf application. I want to bind linq expression to ListView: lv_Results.DataContext = store.Where(x => x.PR > 5); But when i add new elements to store collection, lv_Results doesnt updates. How can i update ListView?

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• Binding to filtered version of collection

  - by Shane Fulmer

  I have a collection that contains all the items that I want to keep track of. I want to display 3 different grids, and in each one I want to display a different filtered version of the items. Is there a way to bind to a filtered version of the main collection without having to maintain 3 separate collections to bind to?

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• MVVM pattern: ViewModel updates after Model server roundtrip

  - by Pavel Savara

  I have stateless services and anemic domain objects on server side. Model between server and client is POCO DTO. The client should become MVVM. The model could be graph of about 100 instances of 20 different classes. The client editor contains diverse tab-pages all of them live-connected to model/viewmodel. My problem is how to propagate changes after server round-trip nice way. It's quite easy to propagate changes from ViewModel to DTO. For way back it would be possible to throw away old DTO and replace it whole with new one, but it will cause lot of redrawing for lists/DataTemplates. I could gather the server side changes and transmit them to client side. But the names of fields changed would be domain/DTO specific, not ViewModel specific. And the mapping seems nontrivial to me. If I should do it imperative way after round-trip, it would break SOC/modularity of viewModels. I'm thinking about some kind of mapping rule engine, something like automappper or emit mapper. But it solves just very plain use-cases. I don't see how it would map/propagate/convert adding items to list or removal. How to identify instances in collections so it could merge values to existing instances. As well it should propagate validation/error info. Maybe I should implement INotifyPropertyChanged on DTO and try to replay server side events on it ? And then bind ViewModel to it ? Would binding solve the problems with collection merges nice way ? Is EventAgregator from PRISM useful for that ? Is there any event record-replay component ? Is there better client side pattern for architecture with server side logic ?

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• Why is two-way binding in silverlight not working?

  - by Edward Tanguay

  According to how Silverlight TwoWay binding works, when I change the data in the FirstName field, it should change the value in CheckFirstName field. Why is this not the case? ANSWER: Thank you Jeff, that was it, for others: here is the full solution with downloadable code. XAML: <StackPanel> <Grid x:Name="GridCustomerDetails"> <Grid.RowDefinitions> <RowDefinition Height="Auto"/> <RowDefinition Height="Auto"/> <RowDefinition Height="*"/> </Grid.RowDefinitions> <Grid.ColumnDefinitions> <ColumnDefinition Width="Auto"/> <ColumnDefinition Width="300"/> </Grid.ColumnDefinitions> <TextBlock VerticalAlignment="Center" Margin="10" Grid.Row="0" Grid.Column="0">First Name:</TextBlock> <TextBox Margin="10" Grid.Row="0" Grid.Column="1" Text="{Binding FirstName, Mode=TwoWay}"/> <TextBlock VerticalAlignment="Center" Margin="10" Grid.Row="1" Grid.Column="0">Last Name:</TextBlock> <TextBox Margin="10" Grid.Row="1" Grid.Column="1" Text="{Binding LastName}"/> <TextBlock VerticalAlignment="Center" Margin="10" Grid.Row="2" Grid.Column="0">Address:</TextBlock> <TextBox Margin="10" Grid.Row="2" Grid.Column="1" Text="{Binding Address}"/> </Grid> <Border Background="Tan" Margin="10"> <TextBlock x:Name="CheckFirstName"/> </Border> </StackPanel> Code behind: public Page() { InitializeComponent(); Customer customer = new Customer(); customer.FirstName = "Jim"; customer.LastName = "Taylor"; customer.Address = "72384 South Northern Blvd."; GridCustomerDetails.DataContext = customer; Customer customerOutput = (Customer)GridCustomerDetails.DataContext; CheckFirstName.Text = customer.FirstName; }

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• 'System.Windows.Data.MultiBinding' is not a valid value for property 'Text'.

  - by chaiguy

  I'm trying to write a custom MarkupExtension that allows me to use my own mechanisms for defining a binding, however when I attempt to return a MultiBinding from my MarkupExtension I get the above exception. I have: <TextBlock Text="{my:CustomMarkup ...}" /> CustomMarkup returns a MultiBinding, but apparently Text doesn't like being set to a MultiBinding. How come it works when I say: <TextBlock> <TextBlock.Text> <MultiBinding ... /> </TextBlock.Text> </TextBlock> But it doesn't work the way I'm doing it?

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• Architectural Composition Languages

  - by C. Lawrence Wenham

  Recently stumbled upon this paper (PDF) talking about ACLs, or Architectural Composition Languages. They're a fusion of two earlier lines of research: Architectural Definition Languages (such as UML) and Object Composition Languages (such as XAML, WWF, or scripting languages). The goal of an ACL is to have a high-level description of a program's architecture which can also be compiled into a runnable program. The high-level description assists automated analysis, while the 'executability' means changes can be tested immediately. You would still author the components of the program in a conventional programming language (C, Java, Python, etc), but they would be composed into a complete program by the ACL. One of the expected benefits is that a program can be ported to a different platform by swapping in "similar but different" components. I've been hankering for something like this for a long time (see this answer I gave on a StackOverflow question a few years ago). The paper mentions that the researchers were working on a language called ACL/1 that initially targeted Java, but would be ported to support .Net as well. However, I can't find any more mention of ACL/1 anywhere. Has there been any more work done on this? Are there any other implementations of the ACL concept that are available for use or experimentation?

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• Set binding for DataTemplate components in code

  - by Chouppy

  Hi; sorry if I'm not clear, it's not really clear in my head too (especially after trying to find my way in other posts :p) What I'm willing to do is creating DataGrids in code, with zero to numerous columns containing a button, which will call one same function but with a "parameter" (different for each column). Here is what I got so far : DataGrid created in code DataTemplate defined in the xaml resources (with a button) DataGridTemplateColumn which uses the above DataTemplate Is it possible to bind the button's properties (in the DataTemplate), to the DataGridTemplateColumn properties (in my case, the column header would be ok), and how? Is there a way to get an access to the DataTemplate components (the button for example) in code, and modify their properties? Is it possible (and not hazardous) to create a DataTemplate in code? I declared mine in xaml because I found a post advising to do so instead of code. Thanks for your help.

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• Wrapping with Dependency Properties

  - by Chris

  I've got a Windows Forms control that I'm wrapping with a WindowsFormsHost-derived class to access WPF's data binding functionality. The Forms control exposes properties that indicate its state, along with the standard property-changed event notifier. For example, a Zoom property on the Forms control is accompanied with a ZoomChanged event. In the WindowsFormsHost wrapper, I'm using a DependencyProperty to represent the underlying Windows Forms control property. Binding works as expected going to the control; however, I'm not sure how to correctly propogate property changes from the wrapped control back out to binding subscribers (i.e., the Windows Form control changes its Zoom property and raises the ZoomChanged event). Any ideas on how to accomplish this? Should I be using a different approach?

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• Bind the value of a parameter in an ObjectDataProvider in WPF

  - by Andrei Rinea

  I would like to be able to be doing this : <ObjectDataProvider x:Key="dataProvider" ObjectInstance="uiRoot:App.Current.Controller" MethodName="GetMyViewModel"> <ObjectDataProvider.MethodParameters> <system:Int32>{Binding Id}</system:Int32> </ObjectDataProvider.MethodParameters> </ObjectDataProvider> The emphasis being on <system:Int32>{Binding Id}</system:Int32> I can't get around this. Any ideas? :(

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• How to handle a DataTemplate creation

  - by Shimmy

  Hello! Take a look at the following xaml: <ListBox ItemsSource="{Binding}"> <ListBox.Resources> <CollectionViewSource x:Key="CVS"/> </ListBox.Resources> <ListBox.DataTemplate> <DataTemplate OnBinding="myBinding"> <ListBox DataContext="{StaticResource CVS}" ItemsSource="{Binding}" /> </DataTemplate> </ListBox.DataTemplate> </ListBox> So I can handle the binding and manually retrieve the CVS and set its Source property to my custom stuff according to the DataTemplate's DataContext. Or else there is a different way in doing it. Any ideas are welcommed!

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• Binding class to ListView

  - by Neir0

  Hi, I have a class public class Foo { public List<string> list1 { get; set;} public List<string> list2 { get; set; } public string url; } and a ListView with two columns How i can to bind instance of Foo class to ListView?

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• How to set the RelativeSource in a DataTemplate that is nested in a HierarchicalDataTemplate?

  - by Dabblernl

  I have the following XAML, that does all that it is supposed to, except that the MultiBinding on the FontSize fails on retrieving the Users. As you can see Users is an IEnumerable<UserData> that is part of the HierarchicalDataTemplate's DataContext. How do I reference it?? <TreeView Name="AllGroups" ItemsSource="{Binding}" > <TreeView.Resources> <HierarchicalDataTemplate DataType="{x:Type PrivateMessengerUI:GroupContainer}" ItemsSource="{Binding Users}" > <Label Content="{Binding GroupName}"/> </HierarchicalDataTemplate> <DataTemplate DataType="{x:Type PrivateMessenger:UserData}"> <TextBlock Text="{Binding Username}" ToolTip="{StaticResource UserDataGroupBox}" Name="GroupedUser" MouseDown="GroupedUser_MouseDown"> <TextBlock.FontSize> <MultiBinding Converter="{StaticResource LargeWhenIAmSelected}"> <Binding ElementName="Root" Path="SelectedUser"/> <Binding RelativeSource="???" Path="DataContext.Users"/> </MultiBinding> </TextBlock.FontSize> </TextBlock> </DataTemplate> </TreeView.Resources> </TreeView>

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• strange Problem with WPF Textbox stringformat - Cursor moves back

  - by Emad

  I am using WPF 4.0 TextBox and binding. I am using StringFormat to format the number as currency. the XAML looks like this: <TextBox Text="{Binding Path=ValueProperty, ValidatesOnDataErrors=True, ValidatesOnExceptions=True, StringFormat={}{0:C}, UpdateSourceTrigger=PropertyChanged}"> </TextBox> Everything seems to work correctly except for a strange behavior: When for example a user types in 12: right after typing 1, the value in the textbox becomes $1.00 and the weird thing is the the cursor is moved to be between the $ and the 1. So when a user simply types in 12, the result becomes $21.00. How can I fix this strange behavior?

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• ToolStripComboBox.SelectedItem change does not propagate to binding source

  - by Marius

  My binding is set up as this: _selectXAxisUnitViewModelBindingSource = new BindingSource(); _selectXAxisUnitViewModelBindingSource.DataSource = typeof(SelectXAxisUnitViewModel); _selectedUnitComboBoxBindingSource = new BindingSource(); _selectedUnitComboBoxBindingSource.DataSource = _selectXAxisUnitViewModelBindingSource; _selectedUnitComboBoxBindingSource.DataMember = "AvailableUnits"; _selectedUnitComboBox.ComboBox.DataSource = _selectedUnitComboBoxBindingSource; _selectedUnitComboBox.ComboBox.DisplayMember = String.Empty; _selectedUnitComboBox.ComboBox.ValueMember = String.Empty; _selectedUnitComboBox.ComboBox.DataBindings.Add("SelectedItem", _selectXAxisUnitViewModelBindingSource, "SelectedUnit", true, DataSourceUpdateMode.OnPropertyChanged); // this is a bug in the .Net framework: http://connect.microsoft.com/VisualStudio/feedback/details/473777/toolstripcombobox-nested-on-toolstripdropdownbutton-not-getting-bindingcontext _selectedUnitComboBox.ComboBox.BindingContext = this.BindingContext; The property "AvailableUnits" is a collection of strings and the "SelectedUnit" is a string-property. Now the dropdown list is populated as expected, but when I select and item in the list, the change is not propagated to the binding source. Any idea what I am doing wrong?

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• Button in a WPF ListItem

  - by Joel Martinez

  Hi, I'm a bit new to WPF. I am working on a list UI where each item in the list will have a set of corresponding buttons to operate on that particular data item. Coming from a web background, I normally would have bound the value into a hidden element in that particular list item or something. However, I just need to find the corresponding technique in this WPF world :-)

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• WPF Binding with RelativeSource of Window Requires "DataContext" in Path?

  - by Phil Sandler

  The following code works, but I'm curious as to why I need the Path to be prefixed with "DataContext"? In most other cases, the path used is relative to DataContext. Is it because I am using a RelativeSource? Because the source is at the root level (Window)? <Style TargetType="TextBox"> <Setter Property="IsReadOnly" Value="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Window}}, Path=DataContext.IsReadOnly}"/> </Style>

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• What is the ideal length of a method?

  - by iPhoneDeveloper

  In object-oriented programming, there is no exact rule on the maximum length of a method , but I still found these two qutes somewhat contradicting each other, so I would like to hear what you think. In Clean Code: A Handbook of Agile Software Craftsmanship, Robert Martin says: The first rule of functions is that they should be small. The second rule of functions is that they should be smaller than that. Functions should not be 100 lines long. Functions should hardly ever be 20 lines long. and he gives an example from Java code he sees from Kent Beck: Every function in his program was just two, or three, or four lines long. Each was transparently obvious. Each told a story. And each led you to the next in a compelling order. That’s how short your functions should be! This sounds great, but on the other hand, in Code Complete, Steve McConnell says something very different: The routine should be allowed to grow organically up to 100-200 lines, decades of evidence say that routines of such length no more error prone then shorter routines. And he gives a reference to a study that says routines 65 lines or long are cheaper to develop. So while there are diverging opinions about the matter, is there a functional best-practice towards determining the ideal length of a method for you?

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• Ajax data two-way data binding strategies?

  - by morgancodes

  I'd like to 1) Draw create form fields and populate them with data from javascript objects 2) Update those backing objects whenever the value of the form field changes Number 1 is easy. I have a few js template systems I've been using that work quite nicely. Number 2 may require a bit of thought. A quick google search on "ajax data binding" turned up a few systems which seem basically one-way. They're designed to update a UI based on backing js objects, but don't seem to address the question of how to update those backing objects when changes are made to the UI. Can anyone recommend any libraries which will do this for me? It's something I can write myself without too much trouble, but if this question has already been thought through, I'd rather not duplicate the work.

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• Wpf binding with nested properties

  - by byte

  ViewModel I have a property of type Member called KeyMember. The 'Member' type has an ObservableCollection called Addresses. The Address is composed of two strings - street and postcode . View I have a ListBox whose item source need to be set to ViewModels's KeyMember property and it should display the Street of all the Past Addresses in the collection. Question My ViewModel and View relationship is established properly. I am able to write a data template for the above simple case as below <ListBox ItemsSource="{Binding KeyMember.Addresses}"> <ListBox.ItemTemplate> <DataTemplate DataType="Address"> <TextBlock Text="{Binding Street}"/> </DataTemplate> </ListBox.ItemTemplate> </ListBox> How would I write the DataTemplate if I change KeyMember from type Member to ObservableCollection< Member assuming that the collection has only one element. PS: I know that for multiple elements in collection, I will have to implement the Master-Detail pattern/scenario.

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