10 C# Developer & Programmer interview questions and answers

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Describe the basic construction of a C# program. Write a simple program that outputs “Hello World” to the console.

A typical C# program consists of a namespace declaration, a class, methods, attributes, a main method, statements, expressions, and comments. A potential example for printing “Hello World” to the console is detailed below.

using System;
namespace HelloWorldApplication
  class HelloWorld
    static void Main(string[] args)
      Console.WriteLine("Hello World");

Can you name three ways to pass parameters to a method in C#?

The three ways to pass a parameter to a method are detailed below.

  • Value Parameters: Passing a parameter to a method by value creates a new storage location for the value parameter. Any changes to the value parameter by the method have no effect on the argument.
  • Reference Parameters: Passing a parameter to a method by reference can be achieved by using the ref keyword. Instead of creating a new storage location for the parameter, the method accesses the memory location of the argument and passes it as a parameter. Changes made to the parameter will also affect the argument.
  • Output Parameters: The out keyword allows a method to return two values from a function. It's similar to passing a reference parameter, except in this case data is being transferred out of the method.

Write a C# method to total all the even numbers in an array of ints.

This is an open-ended coding question that is likely to produce a variety of answers. What you’re really looking for is how the developer chooses to solve the problem. Do they settle for the obvious one-liner, return intArray.Where(i => i % 2 == 0).sum() or will they notice the high probability of overflow and instead opt for something more nuanced like the sample answer below?

static long TotalAllEvenInts(int[] intArray) {
  return (from i in intArray where i % 2 == 0 select (long)i).Sum();

Experienced C# developers will take this as an opportunity to show off their knowledge of C# language constructs that make simple solutions like the one above possible.

What is Operator Overloading and how does it work?

Most of the built-in operators available in C# can be overloaded or redefined using the operator keyword. The sample code below depicts the syntax used to implement the addition operator (+) for a user-defined class.

public static Rectangle operator+ (Rectangle b, Rectangle c)
  Rectangle rectangle = new Rectangle();
  rectangle.length = b.length + c.length;
  rectangle.breadth = b.breadth + c.breadth;
  rectangle.height = b.height + c.height;
  return rectangle;

What is the difference between dynamic type variables and object type variables in C#?

The difference between dynamic and object type variables has to do with when the type checking takes place during the application lifecycle. Dynamic type variables handle type checking at run time, while object type variables handle type checking during compile time.

How does C# handle encapsulation?

Encapsulation is a classic object-oriented design principle that reduces coupling between objects and encourages maintainable code. It involves enclosing objects within a logical package by limiting access to implementation details. In C#, this is accomplished through the access specifiers—public, private, protected, internal, and protected internal.

Predict the output of the code below.

delegate  void Iterator();

static void Main()
  List iterators = new List();
  For (int i = 0; i < 15; i++)
    iterators.Add(delegate { Console.WriteLine(i); });

  Foreach (var iterator in iterators)

This program tests the prospective developer on their experience working with loops and delegates. At first glance, one would expect the program to output the numbers 0 to 15, fifteen times. Instead, the number 15 is printed fifteen times. Since the delegate is being added within the for loop, and because the delegate is only referencing the variable i instead of the value itself, the loop sets the value of the variable i to 15 before it is invoked within each delegate.

Explain nullable types in C#.

Nullable types are data types that, in addition to their normal values, also contain a defined data type for null. Nullable types exist to help integrate C#, which generally works with value types, and databases, which often use null values. You can declare a nullable type in C# using the following syntax:

?  = null;

Explain the role of structs in C#. Why would you choose to define a type as a struct instead of a class?

Structs are used to create structures, a value type that is used to represent a record. Structs play a similar role to classes, which are a reference type in C#. Since structs are value types, they are allocated and deallocated on the stack or inline in containing types. This generally makes structs cheaper to allocate or deallocate than classes, which are reference types. Reference types are allocated on the heap and garbage-collected, which tends to take up more resources. If the instances of a type are small and short-lived, it makes sense to define a value type using structs. The opposite is true when it comes to boxing and unboxing. A value type can get boxed when it is cast to a reference type or some other interface it implements. Because boxes are objects allocated to the heap and deallocated via garbage collection, too much boxing and unboxing of a value can negatively impact performance. Reference types like classes are preferred in these situations.

What are some of the features of generics in C#?

Generics allow a developer to define a class or method that can work with virtually any data type by delaying specification of the programming elements' data types until they are needed. Generics come with a number of features.

  • They make C# code reusable, type safe, and performance optimized.
  • They allow the developer to create generic classes, methods, events, delegates, and interfaces.
  • They allow the developer to create generic collection classes in the System.Collections.Generic namespace.
  • They make it possible to get real-time information on the types used in a generic data type at runtime via reflection.
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    vsuc_fltilesrefresh_TrophyIcon C#
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  • $15 hourly
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    • 4.7
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    Surat, GJ
    vsuc_fltilesrefresh_TrophyIcon C#
    Ecommerce Website Development
    MVC Framework
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    I am here to apply myself and my experience in developing web applications with all my zeal, freedom & enhanced responsibilities. I have worked for various organization for past 6+ years primarily in web developments and have very good grip on OOPS Concept, Reflection, Binding etc.. I have experience of working with various technologies, programming languages & framework. 1. ASP.Net MVC 2. WPF (Windows Presentation Foundation) 3. HTML 4. Javascript 5. Jquery 6. React.JS 7. Bootstrap 8. CSS 9. Kibo eCommerce 10. Backbone js I attribute my hard working, sincerity & eagerness to learn to the success of my short career till now. I am flexible and open to suggestions every time and in every situation. Hoping to have a great career enhancement here at oDesk.
  • $95 hourly
    Stephen T.
    C# Developer & Programmer
    • 5.0
    • (40 jobs)
    Flourtown, PA
    vsuc_fltilesrefresh_TrophyIcon C#
    Microsoft Access
    Microsoft SQL Server
    Microsoft Power Automate
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    Process Design
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    My mission throughout my career is to build systems that help improve the speed, quality, and output of performing critical tasks. All businesses have clerical, complex, error-prone, and time-consuming tasks. Offloading this work onto a software tool or automation process will improve costs and schedule and avoid clerical errors. In many cases, it'll also improve your sanity! I'm a technology-focused engineer with 2+ years of freelancing full-time. Before that, I spent 11 years working in an enterprise manufacturing environment. I have a degree in Mechanical Engineering, but I am also a lifelong computer nerd. I started as an entry-level Project Engineer, becoming the Lead Project Engineering. I then changed roles to Lead Process Engineer and then to Lead Software/Automation Engineer. The trajectory shows my increasing interest and skillset in designing and building software tools to improve all business areas. I've created systems to support engineering, operations, accounting, supply chain, sales, and more, working closely with stakeholders and subject matter experts. This wide range of experiences has most notably developed two key strengths that allow me to serve my clients best: 1) Technical ability to generate effective and reliable software solutions 2) Ability to understand a wide range of key business processes, allowing me to design solutions geared toward specific goals and end-user needs. SOFTWARE AND IT EXPERIENCE - Expert-level user in Excel Automation and advanced VBA macros. (Including interfacing with SQL and other external data sources, files, and APIs) - ERP software integration with software tools above interfacing with ERP system data or supplementing ERP shortcomings. (Direct experience with SAP, Oracle, Kinaxis, Infor LN, and more) - Utilizing and developing all Microsoft Office 365 tools such as Power Automate, Power Apps, Power BI, Lists, Forms, Teams, etc. - SQL Administration (Primary experience with SQL Server and Azure SQL. Some experience with Postgres) - Python. Scripting automation of IT processes and data analytics (Pandas). Also, experience in building both desktop applications (PyQt5) and web applications (Flask and Plotly-Dash) - Sharepoint Administration. Experience launching and maintaining Sharepoint usage for department content, file management, and document control process. - C# / WPF / Winforms desktop applications I have developed custom software solutions to support business processes such as: - Engineering analysis, calculations, and validation (Custom Product Configurator) - Bill of Material and Labor detailed cost analysis tools - Quoting Process Automation (Request for Quote through Delivery) - Inventory and Supply Chain Data Tracking and Analysis - Accounting process automation - Automated PC processes. Document creation, data entry, and more - ERP data design and add-on tools (Baan and SAP experience) - Data mining, aggregation, cleaning, etc. ETL. (Including data migration processes) - API Integration with custom software tools with OAuth Authentication via Excel / VBA or Python - KPI Metrics, Charts, Pareto's, Animated Charts, Data Visualization - Order Confirmation, manufacturing instructions, inspection data processing, etc.
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