Interviewing

How to Answer WPF Interview Questions With Examples

If you’re interviewing for a job such as a software engineer or web developer, WPF is an essential skill that employers want to make sure you have. If you are currently preparing for an interview, you might want to know the most commonly asked questions concerning this widely used application. This article shares some commonly asked interview questions concerning WPF, along with example answers.

Why do employers ask WPF questions?

Employers value tech professionals who know the latest trends and development of their industries. In the information technology sector, building applications is one of the most important fields. Given that WPF is a powerful framework to develop apps, interviewers want to verify that their candidates understand the key concepts.

Examples of WPF interview questions and answers

Here are some questions an interviewer may ask you to test your knowledge of WPF:

What is WPF?

Employers ask this question to verify that you know the basics of WPF. It is also a good way to test your communication skills and your ability to explain a technical term. When giving your answer, define the term as simply as possible. 

Example: ‘WPF stands for Windows Presentation Foundation. It is an application introduced by Microsoft. WPF provides the same functionality of Flash and HTML, a rich user interface and animation that boost application development. For example, WPF allows you to create and animate 3D graphics, download and play video and audio files and provide uniform graphical elements like color gradients.’

What is Prism in WPF?

Employers ask this question to check if you know the official method to use to build applications. To answer, start by stating what it is and what purpose it serves.

Example: ‘Prism is the official guide from the Microsoft practice and patterns team. It provides directions to build composite applications in WPF and Silverlight. It recommends a modular method to divide the complexity of large applications into simpler modules.’

Explain MVVM and its advantages

This is a more difficult question because it verifies both your theoretical and practical knowledge concerning WPF. By asking you to list the advantages, the employer tests your experience with the framework and your judgment abilities. To answer, start by breaking down the acronym and explain its different parts. Then, list the advantages. 

Example: ‘MVVM stands for Model View ViewModel. It is a framework used to make applications in WPF, allowing the developer and designer to work together. MVVM improves the structure of coding by dividing the user integration code into three parts: Model, View and ViewModel. Model is a set of classes containing data collected from databases, and View is the user interface, including the style and theme, the navigation page or controls. ViewModel presents all the data in an easily understandable manner. MVVM offers the advantage of being modular. It separates the business layer and UI as ViewModel and view. It allows code sharing between forms and pages. It is also easy to maintain. Moreover, it improves the design-develop workflow. The commercial application Microsoft Expression, for example, was built using MVVM.’

What is a value converter in WPF?

Among the concepts employers want you to know, the value converter and freezable objects definition are some of the most commonly asked questions. To answer, define the term and explain why it is useful.

Example: ‘A value converter is a function that creates a bridge between a target and a source. It is useful when a target is associated with one source.’

How can elements in a ListBox be sorted?

Interviewers ask this question to test your practical ability to use WPF and your tutorial skills. To answer, give a short and clear explanation of what a developer would see on the screen. 

Example: ‘You can sort elements by using a property of the ItemsCollection object. ItemsCollection includes a SortDescriptions attribute that defines the elements sorting.’

What is the difference between page and window controls in WPF?

Employers ask this question to check your understanding of the main difference between Page and Window controls. It’s important to make sure your answer to this question is simple and straightforward. 

Example: ‘The fundamental difference is that Page Control manages the hosted browser applications. However, Window Control controls Windows Application. Therefore, Window control can contain Page Control, but Page Control cannot hold Window Control.’

How is Silverlight different from the WPF browser application?

During your interview, the hiring manager may ask you to compare two application frameworks to see if you are informed about the industry you want to work in. The quality of your comparison will demonstrate your ability to make the best choices when you need to develop an application for the company.

Example: ‘One of the main differences is that Silverlight only needs the plug-in to run on the client machine, whereas WPF browser applications require a .NET framework. Another difference is that WPF applications depend on the OS, and .NET framework only runs on Windows. Silverlight plug-in, however, can be installed on a non-Windows operating system.’

What are resources in WPF?

When employers ask you about resources, they expect more than a definition. They want to verify that you fully understand what they allow a programmer to do. Illustrate your answer with examples to demonstrate your understanding of the concept. 

Example: ‘In WPF, resources enable establishing the properties of multiple controls at a time. For example, it is possible to set the background on various elements in a WPF application with only one resource. When you define a resource for an element, it also applies to their child elements. For example, when you define the background for a Window element that has a Grid as a child element, the grid element will have the same background. However, a resource you define for a child element only applies to the child element.’