When preparing for a C# interview with five years of experience, it is crucial to focus on questions related to advanced concepts and best practices in C#. Here, I have compiled a list of 35 C# interview questions that are perfect for someone with five years of experience.
The average salary for a C# developer in the United States can vary widely depending on several factors, including experience, location, skill set, and the complexity of projects they can handle.
Experience Level | Average Annual Salary (USD) | Range (USD) |
---|---|---|
Entry-Level (0-2 years) | $50,000 – $70,000 | Varies by location |
Mid-Level (3-5 years) | $70,000 – $110,000 | $60,000 – $130,000 |
Senior-Level (6+ years) | $95,000 – $135,000 | $80,000 – $160,000+ |
For mid-level developers, here’s a breakdown by some of the major tech cities:
City | Average Salary for Mid-Level C# Developer (USD) |
---|---|
San Francisco | $100,000 – $150,000 |
New York City | $90,000 – $140,000 |
Seattle | $90,000 – $135,000 |
Chicago | $75,000 – $115,000 |
Austin | $70,000 – $110,000 |
C# Interview Questions and Answers for 5 Years Experience
Here is the list of 35 interview questions and answers for 5 years of experience in C#.
Q-1. Explain how LINQ improves code readability and maintainability
LINQ (Language Integrated Query) in C# allows us to query collections like arrays, lists, and databases in a declarative way. It improves code readability by enabling us to write queries similar to SQL syntax, and it reduces the amount of boilerplate code we have to write. Maintainability is improved because queries are concise and easier to understand, making it simpler to update or modify them in the future.
Q-2. Discuss the use of try-catch blocks in async methods
In C# async methods, exceptions are propagated via the returned Task. To handle exceptions in async methods, we can use try-catch blocks. The try block contains the async operations, and the catch block handles any exceptions that occur. This way, we can handle exceptions asynchronously and maintain the responsiveness of our application.
Q-3. Provide examples to illustrate the differences between IEnumerable and IQueryable
IEnumerable and IQueryable are both interfaces used for querying collections in C#. IEnumerable is used for querying in-memory collections like arrays and lists, while IQueryable is used for querying out-of-memory collections like databases. The main difference between them is that IEnumerable executes queries in memory, while IQueryable executes queries in the data source.
Q-4. Discuss how Dependency Injection supports better testability and maintainability
Dependency Injection (DI) is a technique used to achieve Inversion of Control (IoC). In DI, dependencies are injected into classes rather than being created within the classes. This improves testability because we can easily replace dependencies with mocks or stubs in tests. Maintainability is improved because dependencies are decoupled from classes, making it easier to change or update them in the future.
Q-5. Explain the code and benefits of using the Singleton Design Pattern
The Singleton Design Pattern ensures that a class has only one instance and provides a global point of access to that instance. The benefits of using the Singleton Design Pattern include improved control over global variables, reduced memory usage, and a single point of configuration.
Q-6. Discuss how async and await improve responsiveness in applications
The async and await keywords in C# enable us to write asynchronous code that doesn’t block the main thread. This improves the responsiveness of our applications, as the UI remains responsive while async operations are being performed in the background.
Q-7. Provide examples of exception handling in multi-threaded applications
In multi-threaded applications, exceptions can occur in any thread. We can use try-catch blocks in each thread to handle exceptions in multi-threaded applications. Additionally, we can use the AggregateException class to handle multiple exceptions that occur in parallel operations.
Q-8. Provide examples to illustrate the differences between a delegate and an event in C#
A delegate is a type that represents a method with a specific signature. An event is a member that enables a class to provide notifications to other classes or objects. The main difference between them is that while delegates can be used to call any method with a matching signature, events can only be used to call methods that have been explicitly added as event handlers.
Q-9. Discuss how yield supports stateful iteration over a collection
The yield keyword in C# is used to create an iterator block that returns an IEnumerable. When the iterator block is called, it returns an enumerator that can be used to iterate over the collection. The yield keyword allows us to maintain the state of the iterator between calls, making it easier to implement stateful iteration over a collection.
Q-10. Provide examples of the using statement in action
The using statement in C# is used to define a scope for objects that implement the IDisposable interface. When the scope exits, the Dispose method is called on the object, releasing any resources it holds. For example:
using (StreamWriter writer = new StreamWriter("file.txt"))
{
writer.WriteLine("Hello, world!");
}
In this example, the StreamWriter is automatically closed and disposed of when the using block exits.
Q-11. Provide examples to illustrate the differences between the “ref” and “out” keywords in C#
The “ref” and “out” keywords are used to pass parameters by reference. The main difference between them is that “ref” parameters must be initialized before being passed, while “out” parameters do not. For example:
void RefExample(ref int x)
{
x = x * 2;
}
void OutExample(out int x)
{
x = 42;
}
In this example, the RefExample method requires that the x parameter be initialized before being passed, while the OutExample method does not.
Q-12. Provide examples to illustrate the differences between “const” and “readonly” in C#
The “const” and “readonly” keywords are used to define constant and readonly fields in C#. The main difference between them is that “const” fields are evaluated at compile-time, while “readonly” fields are evaluated at runtime. For example:
class Example
{
const int ConstField = 42;
readonly int ReadonlyField;
public Example(int x)
{
ReadonlyField = x;
}
}
In this example, the ConstField is a compile-time constant, while the ReadonlyField is a runtime constant.
Q-13. Discuss the benefits of lazy loading and provide examples
Lazy loading is a technique used to delay the loading of resources until they are actually needed. The benefits of lazy loading include improved performance and reduced memory usage. For example:
Lazy<int> lazyInt = new Lazy<int>(() => 42);
int value = lazyInt.Value; // The lambda expression is evaluated here
In this example, the lambda expression is not evaluated until the Value property is accessed, delaying the loading of the resource.
Q-14. Provide examples to illustrate the differences between “dynamic” and “var” in C#
The “dynamic” and “var” keywords are used to define dynamic and implicitly-typed variables in C#. The main difference between them is that “dynamic” variables are evaluated at runtime, while “var” variables are evaluated at compile-time. For example:
dynamic dynamicVar = 42;
var varVar = 42;
In this example, the dynamicVar variable is a runtime variable, while the varVar variable is a compile-time variable.
Q-15. Discuss various strategies for handling errors in C# applications
There are several strategies for handling errors in C# applications, including try-catch blocks, exception filters, and custom exception classes. Try-catch blocks are used to catch and handle exceptions, while exception filters are used to specify conditions under which an exception should be caught. Custom exception classes can be used to define application-specific exceptions.
Q-16. Provide code examples and discuss the benefits of using the Observer Design Pattern
The Observer Design Pattern is used to define a one-to-many dependency between objects, where a change in one object results in a notification and automatic update of the dependent objects. For example:
class Observer : IObserver<int>
{
public void OnNext(int value)
{
Console.WriteLine($"Received: {value}");
}
}
class Observable : IObservable<int>
{
private List<IObserver<int>> observers = new List<IObserver<int>>();
public IDisposable Subscribe(IObserver<int> observer)
{
observers.Add(observer);
return new Unsubscriber(observers, observer);
}
public void Notify(int value)
{
foreach (var observer in observers)
{
observer.OnNext(value);
}
}
}
In this example, the Observer class is notified and updated whenever the Observable class calls the Notify method.
Q-17. Provide examples to illustrate the differences between a struct and a class in C#
A struct is a value type, while a class is a reference type. The main difference between them is how they are stored in memory. For example:
struct StructExample
{
public int Field;
}
class ClassExample
{
public int Field;
}
In this example, the StructExample is a value type, while the ClassExample is a reference type.
Q-18. Discuss various strategies for ensuring thread safety in C# applications
There are several strategies for ensuring thread safety in C# applications, including the use of locks, the Monitor class, and the Interlocked class. Locks are used to synchronize access to shared resources, the Monitor class provides a higher-level abstraction for locks, and the Interlocked class provides atomic operations for updating variables.
Q-19. Discuss the latest features in C# and how they improve the language
The latest version of C# includes several new features that improve the language, such as pattern matching enhancements, record types, and init-only setters. These features make it easier to write concise and expressive code in C#.
Q-20. Discuss strategies for identifying and fixing memory leaks in C# applications
Memory leaks in C# applications can be identified using tools like the .NET Memory Profiler and Visual Studio’s diagnostic tools. Once identified, memory leaks can be fixed by ensuring that objects are properly disposed of and that references to objects are released when they are no longer needed.
Q-21. Provide examples to illustrate the differences between “static” and “instance” methods in C#
“Static” methods are methods that belong to a class rather than an instance of the class. “Instance” methods are methods that belong to an instance of a class. For example:
class Example
{
public static void StaticMethod()
{
Console.WriteLine("Static method");
}
public void InstanceMethod()
{
Console.WriteLine("Instance method");
}
}
In this example, the StaticMethod is a static method, while the InstanceMethod is an instance method.
Q-22. Provide code examples and discuss the benefits of using the Factory Design Pattern
The Factory Design Pattern is used to create objects without specifying the exact class of the object that will be created. For example:
class Factory
{
public static Example CreateExample()
{
return new Example();
}
}
class Example
{
public void Method()
{
Console.WriteLine("Method");
}
}
In this example, the Factory class creates an instance of the Example class without specifying the exact class of the object.
Q-23. Discuss how volatile supports synchronization in multi-threaded applications
The “volatile” keyword in C# is used to ensure that a field is always accessed directly from memory, rather than from a CPU cache. This ensures that changes to the field are immediately visible to all threads, providing a simple form of synchronization in multi-threaded applications.
Q-24. Discuss various strategies for improving performance in C# applications
There are several strategies for improving performance in C# applications, including the use of parallel processing, lazy loading, and caching. Parallel processing allows us to take advantage of multiple CPU cores, lazy loading reduces the amount of resources that need to be loaded initially, and caching allows us to reuse previously calculated results.
Q-25. Discuss various strategies for handling configuration settings in C# applications
Configuration settings in C# applications can be handled using various strategies, including the use of configuration files, environment variables, and command-line arguments.
Configuration files allow us to store configuration settings in a separate file, environment variables allow us to store configuration settings in the environment, and command-line arguments allow us to pass configuration settings to the application at runtime.
Q-26. How do you handle exceptions in a C# application?
In C# applications, exceptions are handled using the try-catch-finally block. The try block contains the code that may throw an exception, the catch block handles the exception, and the finally block contains code that is executed after the try and catch blocks, regardless of whether an exception occurred or not.
Q-27. Can you provide an example of how to use async and await in C#?
Here’s an example of using async and await in C#:
async Task<int> ExampleAsyncMethod()
{
await Task.Delay(1000); // Simulate an asynchronous operation
return 42;
}
async Task CallerMethod()
{
int result = await ExampleAsyncMethod();
Console.WriteLine(result);
}
Q-28. What are some benefits and drawbacks of using asynchronous programming in C#?
Some benefits of using asynchronous programming in C# include improved application responsiveness and the ability to perform multiple operations concurrently. A drawback is that asynchronous code can be more complex to write and understand than synchronous code.
Q-29. Can you provide an example of a custom exception class in C#?
Here’s an example of a custom exception class in C#:
class MyException : Exception
{
public MyException() { }
public MyException(string message)
: base(message) { }
public MyException(string message, Exception inner)
: base(message, inner) { }
}
Q-30. How do you implement the Singleton Design Pattern in C#?
Here’s an example of implementing the Singleton Design Pattern in C#:
class Singleton
{
private static readonly Singleton instance = new Singleton();
private Singleton() { }
public static Singleton Instance
{
get { return instance; }
}
public void Method()
{
Console.WriteLine("Method");
}
}
Q-31. What is the difference between a class and a struct in C#?
A class is a reference type, while a struct is a value type. This means that when a class is assigned to a new variable, the new variable references the same object as the original variable, while when a struct is assigned to a new variable, the new variable gets a copy of the original variable’s value.
Q-32. How do you manage configuration settings in a C# application?
Configuration settings in a C# application can be managed using the ConfigurationManager class, which allows us to retrieve settings from an App.config or Web.config file.
Q-33. What is the difference between the “ref” and “out” keywords in C#?
The “ref” keyword is used to pass a variable by reference, allowing the method to modify the variable’s value. The “out” keyword is also used to pass a variable by reference, but it does not require the variable to be initialized before being passed to the method.
Q-34. Can you provide an example of using LINQ in C#?
Here’s an example of using LINQ in C#:
List<int> numbers = new List<int> { 1, 2, 3, 4, 5 };
var evenNumbers = from n in numbers
where n % 2 == 0
select n;
foreach (var number in evenNumbers)
{
Console.WriteLine(number);
}
Q-35. What is the difference between “const” and “readonly” in C#?
A “const” field is a compile-time constant, meaning its value is set at compile-time and cannot be changed. A “readonly” field is a runtime constant, meaning its value can be set at runtime, but once set, it cannot be changed.

Conclusion
The questions and answers provided above cover a range of topics that are relevant to C# developers with 5 years of experience, from basic concepts to advanced features and best practices. I hope that these questions and answers will be useful in preparing for your next C# interview and help you demonstrate your expertise in the language.
I hope these 35 C# Interview Questions for 5 Years Experience will help you get a job.
You may also like:
- C# Interview Questions and Answers for Experienced Professionals
- Best C# Interview Questions and Answers for Freshers
- .Net Core Interview Questions and Answers for Experienced Professionals
Bijay Kumar is a renowned software engineer, accomplished author, and distinguished Microsoft Most Valuable Professional (MVP) specializing in SharePoint. With a rich professional background spanning over 15 years, Bijay has established himself as an authority in the field of information technology. He possesses unparalleled expertise in multiple programming languages and technologies such as ASP.NET, ASP.NET MVC, C#.NET, and SharePoint, which has enabled him to develop innovative and cutting-edge solutions for clients across the globe. Read more…