We'll find out later that this is a mistake - but for now let's just go with it! I tried to do it in a code-behind but is did not work. Thus, when the host window is designed, the control will ignore the window's design-time view model passed to it as DataContext and will properly bind to the controls dependency properties: The described above usage of design-time data binding is just a trick, not an all-encompassing solution, but it should work for most of the user controls. Can airtags be tracked from an iMac desktop, with no iPhone? How to define 'Attached property' as 'SelectedValuePath' in ComboBox? Run your app. To learn more, see our tips on writing great answers. DataContextWPF. Window.DataContextWindow, This is a summary of the above link. At the same time, when we design the window hosting our user control, the window constructor again will not be executed, but the control constructor will. If the control is depending on some VM or is tightly coupled / depends on being placed into a specific context to work then it isn't a "control". Is a PhD visitor considered as a visiting scholar? However, in most cases, like this one, you will find that there are some elements of your user control that you wish to configure. The control is populated with design-time data via its properties. combo box inside a user control disappears when style is applied in wpf. The following articles describe design-time data binding in detail: The most important of the design-time attiributes is d:DataContext. Again, this is a DataContext issue, the binding in our user control is on a Shoesize property, whilst the DataContext is now the FieldUserControl instance. How to react to a students panic attack in an oral exam? Hi, Instead, nest it one Element deep in the XAML, in your case, the StackPanel. I have a custom component that declares a DependencyProperty. Is it suspicious or odd to stand by the gate of a GA airport watching the planes? And the view (no code behind at the moment): The problem is that no data is displayed simply because the data context is not set. We already have the Label dependency property, we now add a Value property: This value property is bound to the user control UI as follows: The idea here is that the exposed Value property 'relays' the value of the binding in our MainPage.xaml, which now has a binding which tells us which model object property is being displayed in our user control: If you compile and run this code you will find that it doesn't work! nullUserControlDataContext, (app:TestControl)DataContext UserControl.DataContext The Binding in the UserControl's XAML is supposed to bind to a property of the UserControl itself, not one of the current DataContext. This makes direct use of the d:DataContext attribute in user controls impossible and one needs to resolve to a trick. B, TextB Thanks to Brandur for making me understand that. A part of the .NET Framework that provides a unified programming model for building line-of-business desktop applications on Windows. A trick that allows populating a user control with sample data while you are designing it in the Visual Studio designer, Figure 1. WPFUserControl.DataContext - This is why our Value binding is failing. This link does a great job for that. wpf - How to set the datacontext of a user control - Stack Overflow I'm creating a UserControl I want to use something like this: So far, I've implemented similar controls like this: where Color and Text are dependency properties of the control defined in code. It preserves the control bindings and doesn't require any specific element naming. How to follow the signal when reading the schematic? I like it. If you set RelativeSource like this, how does it know what is the VM of this control? This preserves the Inheritance. Instead it's DataContext seems to be null. C# Copy public MainPage() { InitializeComponent (); this.DataContext = new BookstoreViewModel (); } But if you do that then your page isn't as "designable" as it could be. Once it finds a non- null DataContext, that object is used for binding. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2, WPF/C# Assigning a ViewModel to a custom control from parent view, Could not load type 'System.Windows.Controls.Primitives.MultiSelector' from assembly PresentationFramework. Question. Asking for help, clarification, or responding to other answers. DataContext, WindowUserControl.DataContext Code is below. We have closed this ticket because another page addresses its subject: DevExpress engineers feature-complete Presentation Controls, IDE Productivity Tools, Business Application Frameworks, and Reporting Systems for Visual Studio, Delphi, HTML5 or iOS & Android development. writing a different title in the first textbox, but you might be surprised to see that this change is not reflected immediately. The DataContext that it passes to the control is ignored within the control. Unless you are setting or binding the usercontrol's datacontext it will be mainwindowviewmodel. Should you have any questions or need assistance from a member of our team, write to us at info@devexpress.com. You shouldn't be encouraging beginners to use anti-patterns that will cause them trouble and frustration. DataContext tabbed MVVM It makes sure that your View is hooked up with ViewModel. We have just found out why! Sample Data in the WPF and Silverlight Designer. Run snoop. () . ncdu: What's going on with this second size column? WPFUserControlBinding C# UserControlBinding UserControl <Button Content= "OK" Width= "75" Margin= "15 8 15 8" x:Name= "ButtonOk" /> ButtonOk CommandWindowBinding xaml .csDependencyProperty Not the answer you're looking for? As an example, let's consider the progress report user control shown in figures 1 and 2. The file that contains the user control also ends with .xaml, and the Code-behind ends with .xaml.cs - just like a Window. I need a DataContext for the Window and another one for the UserControl. If a law is new but its interpretation is vague, can the courts directly ask the drafters the intent and official interpretation of their law? You may however set the DataContext of the root element in the UserControl's XAML to avoid setting RelativeSource on potentially many Bindings: Try this and you don't need to use any RelativeSource in binding: Thanks for contributing an answer to Stack Overflow! As an aside, for bonus points, you can bind the layout root DataContext without any code-behind by using an ElementName binding as follows: Or, in WPF you could event use a RelativeSource FindAncestor binding, with AncestorType set to the type of FieldUserControl (but that would just be showing off!). Hi, if you use the same instance of ViewModel for Master and Child Window you can bind Controls to the same property in ViewModel (instance). Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages. c#/WPF (DataContext = obj)(subclass.var} DataContext is inherited to all lower Elements of the XAML and to all the XAML of UserControls unless it is overwritten somewhere. A Simple Pattern for Creating Re-useable UserControls in WPF / Silverlight. In our MainPage.xaml we have attempted to bind the Value property of the FieldUserControl to the Height property on our model object. WPF UserControl: DataContext 1 1 3 Thread WPF UserControl: DataContext archived 8484a1fc-4c0e-4b12-9e78-5767c44e204d archived521 This forum has migrated to Microsoft Q&A. VisitMicrosoft Q&Ato post new questions. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Using the DataContext property is like setting the basis of all bindings down through the hierarchy of controls. It can be set for any FrameworkElement and specifies the design-time DataContext for a control and its children. , Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. You can set the datacontext to self at the constructor itself. Thus, if we create a design-time view model which shape matches control's dependency properties and pass it as design-time sample data via d:DataContext to the designed user control, the control child elements will see it: Due to the matching shape, the designer will successfully bind the user control elements to the properties of the design-time view model and we will get the control view shown in figure 2. As already shown, the final result looks like this: Placing commonly used interfaces and functionality in User Controls is highly recommended, and as you can see from the above example, they are very easy to create and use. WPF user control binding not worked - Microsoft Q&A The designer then uses the context to populate the control binding in the Design view and to display sample data in . The DataContext is a wonderful property, you can set it somewhere in the logical tree and any child control can just bind to properties without having to know where the DataContext was set. By setting the UserControl DataContext to itself, this overwrites the DataContext and breaks Inheritance. ; ; WPF UserControl - , ? My blog includes posts on a wide range of topics, including WebAssembly, HTML5 / JavaScript and data visualisation with D3 and d3fc. Using Kolmogorov complexity to measure difficulty of problems? Notice that because of all these bindings, we don't need any C# code to update the labels or set the MaxLength property on the TextBox - instead, we just bind directly to the properties. Upgrade to Microsoft Edge to take advantage of the latest features, security updates, and technical support. Why is there a voltage on my HDMI and coaxial cables? The WPF / Silverlight binding framework revolves around the concept of dependency properties, you can make any property the source of a binding, but the target must be a dependency property (DP).