Windows Presentation Foundation (WPF) is one such tool that helps developers in building applications by separating the UI framework. It uses the Extensible Application Markup Language (XAML) with the .Net framework for development. In this post, we will explain about the top 30 WPF interview questions. Go through the below frequently asked WPF interview questions and answers to elevate your learning curve.
Ans: WPF architecture consists of 5 main components.
Ans: Content alignment is used to change the position of text in text boxes and buttons. The content alignment is of 2 types - horizontal content alignment and vertical content alignment. These properties are set in the System.Windows.Controls.Control class. The left and top are the default vertical and horizontal alignment of the content of a text box. The center is the default alignment of content on a button.
Ans: In WPF, resources enable the developers to reuse commonly defined objects and values. Using resources, we can set properties of multiple controls at a time. If we define a resource for an element, the same will be applied to the child elements of that element too.
Ans: WPF supports two types of documents.
Ans: The Extensible Application Markup Language (XAML) is used to instantiate .NET objects. It describes the objects, properties, and the relation between them. It helps in writing user interfaces for web applications by creating graphical and non-graphical objects. In WPF, XAML is used to encompass the elements of content like controls, documents, and vector graphics.
Ans: The styles in WPF are resources that allow developers to apply some properties to the controls all over the application. We can set the existing properties of an object like width, height, size, font, etc. The styles can be applied to the parent element, root element, current element, and on the application level.
Ans: A value converter works as a bridge between a target and a source. It is required when a target is bound with one source. The value converter can convert the string data to Boolean. To use a value converter, we should inherit it from the I Value Converter in the System.Windows.Data namespace.
Ans: Controls in WPF are of 4 types.
Ans: Xmlns is the default namespace used to resolve overall WPF elements. The xmlns:x is used to resolve the XAML language definition.
Ans: A freezable object is an object that has its state locked down, so it becomes unchangeable. When an object is frozen, we cannot modify it. When an object is unfrozen, it behaves like any other object. The freezable objects perform better, and they are safer to share between threads.
Ans: The DependencyObject has the following methods in it.
Ans: PRISM is a framework to create complex applications in Silverlight and WPF that have a single code base. It divides a complex application into simpler modules. It helps to build rich and flexible desktop applications easily. It uses Command Patterns, DI, IC, Separation of Concerns, MVVM, etc.
Ans: We can use Windows Forms in a WPF application. It can appear as a WPF popup. Instead of dropping controls on windows forms, we can place them beside WPF controls.
Ans: There are three assemblies in WPF.
Ans: WPF consists of three types of windows.
Ans: The syntax for resource is,
Ans: All the elements in a WPF application are set in an element tree relationship. Routed event is similar to a normal event, which helps with the hierarchy of the controls. Routed events help the events to tunnel down the tree to the target elements or bubble up to the root element. The routed events are of 3 types - bubbling events, tunneling events, and direct events.
Ans: The WPF comes with the below five built-in layout panels.
Ans: The following are the important subsystems in WPF.
Ans: When the built-in controls do not satisfy your needs, you can create a custom control. If you want to add extra functionality or an extra property, you can create a custom control. Custom control helps in creating feature-rich and customizable controls. The best way to make a control library is through custom control. It offers its own style, theme, and template defined in generic.xaml.
Ans: The command design pattern is under the behavioral design patterns category. It decouples the request of action from the object. It represents an action as an object. It does not contain an executable functionality. It promotes loose coupling by removing the direct link between the functionality and the command definitions. The command design pattern lets developers implement operations based on the user request. The members of the command design pattern are,
Ans: A Dispatcher object represents an object that is associated with a Dispatcher. When a WPF application is executed, it automatically creates a new Dispatcher object. Two threads will be created when a WPF application starts - Render thread and UI thread. The Dispatcher will be associated with the UI thread. The Dispatcher object can only be accessed directly through the thread that the Dispatcher was created on.
Ans: The view is the layout, structure, and appearance of what the user sees on the screen, i.e., the user interface. It receives user's interaction through a click, keyboard, gestures, etc. It uses data binding to forward these interactions to the view model.
The view model is actually a logic that functions as a link between model and view. It retrieves data from the model and exposes it to the view. It can be described as a state of the data in the model. The view model does not have a reference to the view. Instead, it binds directly properties on the view model.
Ans: A trigger is defined to perform an action on a change of any property value or when an event fires. They are used in styles, and they create a visual effect on controls. The following are the triggers provided in WPF.
Ans: Both commands and events are related to each other. Unlike events, commands can be associated with any number of UI Controls or Input Gestures. The events don't really fit into the MVVM paradigm. So, we generally use commands in WPF MVVM architecture.
Ans: An adorner is a special framework element that is bound to the UI element and rendered on a surface above the element. This surface is called an adorner layer. We can extend controls by adding extra visual functionality using adorners. They are also used to add handles to elements that provide visual clues to the user.
Ans: Strong skills in .NET programming is a prerequisite for WPF developers. If you are an experienced WPF developer, knowledge of coding implementation best practices, multithreading concepts, design patterns, integration testing, and unit testing will be an added advantage. You should be able to react to problems on the go and correct the program as necessary. The job opportunities for WPF are still high in number. So, prepare well and crack the interview for your dream job.
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