Hiring guide for C# Engineers

C# Developer Hiring Guide

C# is a modern, object-oriented programming language developed by Microsoft in 2000 as part of its .NET initiative (Microsoft, 2000). It was designed by Anders Hejlsberg, who also contributed to the development of Turbo Pascal and Delphi (Microsoft, 2000). C# is heavily influenced by C and C++, but it also incorporates elements from Java and other languages, aiming to simplify coding and enhance developer productivity (ECMA International, 2002). It is widely used for developing desktop applications, web services, and games, particularly on the Windows platform (Microsoft, 2020). C# continues to evolve, with regular updates providing new features and improvements to the language (Microsoft, 2020).

Ask the right questions secure the right C# talent among an increasingly shrinking pool of talent.

First 20 minutes

General C# app knowledge and experience

The first 20 minutes of the interview should seek to understand the candidate's general background in C# application development, including their experience with various programming languages, databases, and their approach to designing scalable and maintainable systems.

How would you declare a variable in C#?
You can declare a variable in C# by specifying the type followed by the variable name. For example, 'int myVariable;' declares a variable named 'myVariable' of type integer.
What are the different types of comments in C# and how are they used?
There are three types of comments in C#. Single line comments which are denoted by '//', multiline comments denoted by '/*' and '*/', and XML comments denoted by '///'. They are used to add descriptive text in the code for understanding and readability purposes.
How would you handle exceptions in C#?
In C#, exceptions are handled using try, catch, and finally blocks. The 'try' block contains the code that may potentially throw an exception. The 'catch' block contains the code that is executed when an exception occurs. The 'finally' block contains code that is always executed, regardless of whether an exception was thrown or not.
What is the difference between a struct and a class in C#?
The main differences between a struct and a class in C# are that structs are value types while classes are reference types, and structs do not support inheritance, but classes do. Also, a struct can't have a default constructor or destructor, but a class can.
What are delegates in C#?
Delegates in C# are similar to function pointers in C or C++. They are type-safe objects that reference methods with a particular parameter list and return type. Delegates allow methods to be passed as parameters.
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What you’re looking for early on

Does the candidate have a solid understanding of C# language fundamentals?
Is the candidate able to solve problems and think critically?
Has the candidate demonstrated the ability to work well in a team?
Can the candidate effectively communicate technical information?

Next 20 minutes

Specific C# development questions

The next 20 minutes of the interview should focus on the candidate's expertise with specific backend frameworks, their understanding of RESTful APIs, and their experience in handling data storage and retrieval efficiently.

How would you implement threading in C#?
Threading in C# can be implemented by using the 'System.Threading' namespace. The 'Thread' class is used to create and control a thread, get its status, and perform other operations like starting, pausing, and resuming a thread.
What is the difference between 'out' and 'ref' parameters in C#?
Both 'out' and 'ref' are used to pass arguments by reference. The difference is that 'ref' requires the variable to be initialized before it is passed while 'out' does not require the variable to be initialized before it is passed to the method.
What are generics in C#?
Generics in C# allow you to define type-safe data structures, without committing to actual data types. This results in a significant performance boost and higher quality code, because you get to reuse data processing algorithms without duplicating code.
How would you implement inheritance in C#?
Inheritance in C# is implemented by using the ':' symbol. For example, if you have a base class 'Animal' and a derived class 'Dog', you would declare the Dog class as 'public class Dog : Animal'. This means that 'Dog' inherits from 'Animal'.
What is the difference between 'is' and 'as' operators in C#?
'is' operator is used to check the compatibility of an object with a given type and it returns the result as Boolean. On the other hand, 'as' operator is used for casting of object to a type or a class. If the casting is not possible it returns null.
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The ideal back-end app developer

What you’re looking to see on the C# engineer at this point.

At this point, a skilled C# engineer should demonstrate strong problem-solving abilities, proficiency in C# programming language, and knowledge of software development methodologies. Red flags include lack of hands-on experience, inability to articulate complex concepts, or unfamiliarity with standard coding practices.

Digging deeper

Code questions

These will help you see the candidate's real-world development capabilities with C#.

What does the following C# code do?
int result = 5 + 7;
This code declares an integer variable named 'result' and assigns it the value of the sum of 5 and 7, which is 12.
What will be the output of the following C# code?
Console.WriteLine(5 == 7);
The output of this code will be 'False' because the equality operator '==' checks if the two numbers are equal, and since 5 is not equal to 7, it returns 'False'.
What does the following C# code do?
List numbers = new List {1, 2, 3, 4, 5};
This code creates a list of integers named 'numbers' with values 1, 2, 3, 4, 5. The 'Reverse' method is then called on the list which reverses the order of the elements in the entire list.
What does the following C# code do?
Thread thread = new Thread(() => {
Console.WriteLine('Hello, World!');
This code creates a new thread and assigns a lambda expression that prints 'Hello, World!' to the console as its thread start delegate. The 'Start' method is then called on the thread object, which causes the delegate to be invoked on the newly created thread.

Wrap-up questions

Final candidate for C# Developer role questions

The final few questions should evaluate the candidate's teamwork, communication, and problem-solving skills. Additionally, assess their knowledge of microservices architecture, serverless computing, and how they handle C# application deployments. Inquire about their experience in handling system failures and their approach to debugging and troubleshooting.

What are lambda expressions in C#?
Lambda expressions are a concise way to represent anonymous methods or functions. They can contain expressions and statements, and can be used to create delegates or expression tree types. They are particularly useful for writing LINQ query expressions.
How would you implement polymorphism in C#?
Polymorphism in C# can be implemented in two ways: compile-time polymorphism (also known as overloading) and runtime polymorphism (also known as overriding). Overloading is achieved by defining multiple methods with the same name but different parameters. Overriding is achieved by using the 'override' keyword to redefine a method in a derived class that has already been defined in the base class.
What is the difference between 'const' and 'readonly' in C#?
'const' and 'readonly' both are used to make a field constant which means once a value is assigned to them, it can't be changed. The difference is that 'const' is compile-time constant whereas 'readonly' is runtime constant. 'const' value is assigned at the time of declaration whereas 'readonly' value can be assigned either at the time of declaration or inside the constructor.

C# application related

Product Perfect's C# development capabilities

Beyond hiring for your C# engineering team, you may be in the market for additional help. Product Perfect provides seasoned expertise in C# projects, and can engage in multiple capacities.