.NET Developer Interview Questions

.NET is Microsoft’s leading development platform for creating quality software solutions. First released in 2002 as a Windows-based framework, it’s one that’s evolved over time to include cross-platform support and an extensive open-source community and ecosystem that now support its use.

For teams and businesses, this means the developers they need to build the same kind of software the framework has always supported is changing. While a Microsoft expert with extensive experience in only .NET technologies might have been an ideal fit in the past, it’s a role better suited today to a more well-rounded engineer with diverse experience and broader specializations.

Open-source technologies have changed how the framework operates and also the team of developers best suited to utilizing it.

To build a team of .NET developers that can enhance your firm, first you have to understand what the technology is and how it can deliver for your teams. Just knowing the fundamentals of .NET development can create an opportunity to understand the kind of developer you need for the role and provide the knowledge and tooling necessary to generate the great conversations that can lead to hiring them.

Starting with what .NET development is and how it can enhance your organization, we’ve created this guide with 7 .NET developer interview questions you should ask to ensure your incoming developers really know their stuff when it comes to the framework.

.NET Development Guide

Over the last 20 years, .NET has evolved into a rich software development platform for creating applications for desktop environments, the web, mobile, and cloud-based platforms. The latest version of the framework, .NET 6, is now entirely open-source, cross-platform, and includes a rich and diverse ecosystem of libraries and tools for teams to lean on.

As a framework, it’s one that’s become highly valued by developers for its near unbeatable scalability and productivity while providing all the tooling and libraries engineers need to create exceptional applications.

The advantages and benefits the framework provides have led it to being nominated as the most highly appreciated tool amongst developers for the last two years in a row.

When it comes to hiring developers to take advantage of the benefits of .NET, organizations have to take care to find the right fit. The developers you choose should have a strong knowledge and familiarity with the framework’s unique advantages. This could mean experience in libraries such as Xamarin, ML.NET, or ASP.NET and a portfolio filled with highly effective applications utilizing these tools.

Finding out about a candidate’s past experience and how they’ve leveraged it to success, is key to understanding the developers you hire and the skills they can bring to your firm. To help you understand, discover, and investigate this experience in the teams you hire, we've put together some key interview questions that can help you get the best from your candidates and find out who you should bring in to build up your teams.

.Net Developer Interview Questions:

1. What’s Your Experience in .NET?

The .NET framework is an exceptionally broad tool when it comes to application development. As a result, the ways developers will have applied it to create applications and services are likely to vary widely.

A great place to start to find the experience you need is to find out what your candidate has done with the framework in the past. This can include the experience they have built up using the various libraries and tools relating to the language and is ideally demonstrated with a portfolio of apps to show.

Relatively unique to .NET, these experiences may range across several languages from Visual Basic and Perl to C# and F#. Look for diverse experiences and applications to create a well-rounded team that can handle most challenges your firm is likely to throw at them.

2. What’s the Difference Between .NET Framework and .NET Core?

Part of the evolution of .NET has inevitably included some shifts in convention and name changes that have left even .NET developers searching for the right terminology. .NET Core is the latest iteration of the .NET framework—a suite of tools that has been simplified and streamlined into a unified ecosystem over the last 10 years. This change also marks a shift to the framework as one that’s open-source and cross-platform, something most candidates should have an interest in and good knowledge of.

Modern characteristics of .NET core include:

• Open-source development. .NET core is now freely distributed under MIT and Apache licenses
• Cross-platform. Development using Windows, Linux, and macOS is now supported with tooling to match
• Consistent API. A single API model written in .NET standard can now be applied across all .NET applications across multiple platforms and languages
• Compatibility. .NET Core tools are now shared across the .NET framework, Mono, and Xamarin through .NET standard

3. What Are the Significant Components that Go Into .NET Core?

Typically, .NET core can be broken down into 5 major components. These are:

• Common Language Runtime (CLR). An execution engine that runs code and provides background services essential to modern application development. Services provided by the CLR include memory management, garbage collection, exception handling, and type safety amongst others
• Framework Class Library (FCL). A useful helper library for developers, the FCL contains predefined methods and properties to implement functions used by .NET applications. Database connections, file input and output, and base types all lean on the FCL
• Base Class Library (BCL). A wider collection than the FCL, the BCL has a large collection of libraries and functions for implementing various languages that .NET supports
• Common Type System (CTS). Allowing developers to define data types across multiple languages, the CTS ensures interoperability between types across multiple languages
• Common Language Specification (CLS). A subset of the CTS, the CLS defines rules for all .NET languages to interact and share data with each other regardless of syntax differences

4. What’s the Difference Between Managed and Unmanaged Code?

Managed code is executed in the CLR, providing additional features and functionality to ensure the reliability and performance of code written by developers. Unmanaged code, in comparison, is run in the operating system targeted by the developer. Writing unmanaged code allows developers to lean on languages and tools independent of the .NET framework.

The advantages of managed code include better system security, more robust applications and platform independence by running within the CLR engine.

5. How Does Garbage Collection Work in .NET?

Garbage collection is common in many modern language tools such as .NET or Java. It’s a method for optimizing memory use and removing unnecessary data to enhance efficiency.

in .NET, memory is divided into three generations: zero, one, and two. Objects in generation 0 are cleaned from memory frequently while one and two store objects for a comparatively long term. To perform this operation, the garbage collector maintains a list of live objects and their references. Objects still live without reference are cleaned from memory and their space is freed for alternate uses.

6. Describe Linq

Language-Integrated Query (LINQ) is a Microsoft programming model that offers a way to sort, filter, and index data using a LINQ-specific syntax to interact with a wide variety of data sources. It’s a tool regularly used by .NET developers to retrieve filtered data from SQL databases, data sets, collections, and XML documents.

7. Explain, in the Simplest Terms Possible, how .NET Applications Are Run

A .NET application is commonly written in one of the frameworks supported languages such as C#, F#, or Visual Basic. When this code is ready it’s compiled to a Common Intermediate Language (CIL) by a native compiler specific to the language being written.

With this assembly file compiled, the CLR takes this and compiles it again into machine code using a Just in Time (JIT) compiler to execute the code on whichever platform it’s being run on.

How to Choose and Interview a .NET Developer

Here, we’ve covered a sample of some of the most critical .NET framework interview questions you can ask to ensure candidates have a thorough knowledge of the .NET ecosystem. Far from complete, there are many other areas of expertise you’d want your next developer to have before choosing to hire them into your firm.

Some of the specific skills and knowledge you might expect a .NET developer to come with might include:

• Object-oriented programming knowledge and experience
• Domain-specific experience in mobile app, web app, or desktop application development
• Evidence of working well in a team environment creating high-quality apps
• Good architecture and design practices when it comes to creating software commercially
• Interpersonal ‘soft skills’ that can add to the team and build a healthy environment

There’s rarely a one-size-fits-all solution when it comes to hiring any kind of developer. Allow room for candidates to surprise you with different sets of skills applicable to your teams or broaden your horizons when it comes to who you plan to hire.

Take a close look at the portfolio and any publicly available code as a key indicator of what a candidate is likely to produce and how they’ll be able to perform within your organization.