35+ Best [ C# ] Interview Questions & Answer [FREQUENTLY ASK]
C# Interview Questions and Answers

35+ Best [ C# ] Interview Questions & Answer [FREQUENTLY ASK]

Last updated on 04th Jul 2020, Blog, Interview Questions

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These C# Interview Questions have been designed specially to get you acquainted with the nature of questions you may encounter during your interview for the subject of C# . As per my experience good interviewers hardly plan to ask any particular question during your interview, normally questions start with some basic concept of the subject and later they continue based on further discussion and what you answer.we are going to cover top 100 C#  Interview questions along with their detailed answers. We will be covering C#  scenario based interview questions, Questions for interview to both freshers as well as experienced. 

1.What is C Sharp?


Developed by Microsoft, C# (pronounced “C-sharp”) is an object-oriented programming language that is both powerful and versatile. When it was first released in the early 2000s, C# was intended to be a powerful and effective language for creating a broad variety of applications, including web and desktop programs. Providing developers with an extensive collection of tools and libraries for application development, it is an essential part of the Microsoft.NET framework.

2. What is the C# “var” keyword used for?


In C#, you can declare local variables with implicit typing by using the “var” keyword. When developers use “var,” the compiler infers the variable type based on the assigned value, negating the need for them to explicitly state it. This preserves strong typing during compilation while improving code readability and flexibility, particularly when working with complex or generic types.

3. In C#, how does exception handling operate?


In C#, try, catch, and finally blocks are used for handling exceptions. The code where an exception might occur is enclosed in the “try” block; specific exceptions or a general exception are handled in the “catch” block; and code that always runs, regardless of whether an exception occurred or not, is contained in the “finally” block. This structure increases the robustness and dependability of C# applications by ensuring a controlled response to unusual circumstances.

4. Value types and reference types differ in the following ways:


  • Storage Location: Heaped Storage on the Stack
  • Data storage keeps track of the actual data as well as references to it.
  • Memory Handling Automatically controlled by the system; garbage collection is necessary.
  • Instances: int, char, bool, float, class, interface, delegate, and array
  • Impact on PerformanceFaster allocation and access in general somewhat slower as a result of heap management.

5. What does C#’s “using” statement accomplished?


In C#The “using” statement provides a simple method for managing resources automatically. It guarantees that items that use the IDisposable interface are disposed of properly. Resource management in C# applications are made efficient and error-proof by enclosing the use of disposable resources inside a “using” block, which allows the system to release the resources when they go out of scope.

6. What distinguishes “readonly” from “const” in C#?


“Readonly” and “const” have different functions when it comes to variable declaration in C#. “const” offers a convenient way to declare immutable values by defining compile-time constants whose values cannot be changed after compilation. Conversely, “readonly” variables are those that stay constant after being assigned during runtime or inside a constructor. They provide flexibility in situations where an object’s lifetime requires an unchanging value to be determined at runtime.

7. What distinguishes “StringBuilder” from “String” in C#?


In C#, a string C# StringBuilder
1 Unchangeable data format. Changeable kind of data.
2 After creation, values cannot be altered. Crafted to manipulate strings effectively.
3 A new string object is created after every modification. Enables the string’s content to be changed dynamically.
4 Ineffective when concatenating a large number of strings. Increased efficiency when concatenating or modifying large strings.
5 Ideal for situations where there aren’t many string changes. Especially helpful for handling regular and dynamic string manipulations.

8. What function does C#’s “abstract” keyword serve?


When defining abstract classes and methods in C#, the “abstract” keyword is essential. Abstract classes are intended to be subclassed because they cannot be instantiated on their own. Concrete implementations of abstract methods declared in the abstract class must be provided by subclasses.

9. In C# What are indexers?


Similar to arrays, indexers in C# offer a way to access the elements of a class or struct instance. They make it possible to define unique access patterns by treating objects as though they were arrays. Developers can improve the readability and usability of code by giving their classes more expressive and intuitive interfaces by overloading the indexing operator.

10. Describe the idea behind “boxing and unpacking.”


In C#, boxing and unboxing require value types to be converted to reference types. Wrapping a value type into an object on the heap so that it can be used as a reference type is known as boxing. On the other hand, unboxing is the process of removing the original value type from the packaged item. These operations allow value-type and reference-type systems in the C# language to integrate seamlessly, and they are essential when working with collections or interfaces that need reference types.

11. What function does C#’s “params” keyword serve?


In C#, a method can accept a variable number of parameters by using the “params” keyword. By enabling the caller to supply a variable number of arguments of a particular type without explicitly creating an array, it streamlines method calls. This makes the code more readable and flexible, especially in situations where the precise number of arguments might change.

12. The “is” operator in C# differs from the “as” operator.


“Is” Operator:

  • Utilized to verify type.
  • Gives back a Boolean value that indicates if an object belongs to the given type.
  • doesn’t actually convert types in any way.
  • useful for branching conditionally depending on the type of object.

“as” Operator:

  • utilized in safe type casting.
  • makes an effort to convert an object to a particular type.
  • Returns null in the event that the cast fails.
  • helpful for converting types without throwing exceptions.

13. In C# How does garbage collection operate?


Memory management in C# is automatically handled by a garbage collector. The garbage collector locates and recovers memory that has been occupied by inoperable or out-of-service objects. It compacts the memory to lessen fragmentation, releases memory from objects that are no longer referenced, and periodically scans the managed heap.

14. What does the C# term “delegates” mean?


In C#delegates act as type-safe function pointers that make callback mechanisms and events possible to implement. They facilitate the assignment of methods as variables or parameters, which enhances the design flexibility of modular and extensible code. In order to facilitate communication between various components of a program, delegated programming is essential.

15. What does C#’s “using” directive serve as?


In C#, the “using” directive is used to include a namespace in the program. It removes the hassle of having to completely qualify every usage by offering a convenient way to reference types and members from a particular namespace. This is an essential component for arranging and structuring C# code since it improves code readability and minimizes possible naming conflicts.

16. Which C# access modifiers are available?



  • Permits entry from any other code.
  • Members are observable beyond the classroom.


  • limits entry within the type that is being contained.
  • Members cannot be seen outside of the classroom.


  • permits access to both the derived types and the containing type.
  • Members are hidden from view from below the class hierarchy.


  • restricts who can enter the current assembly.
  • It is impossible to see members outside of the assembly.

17. How is multithreading implemented in C#?


There are several ways to implement multithreading in C#: the Task Parallel Library (TPL) for easier asynchronous programming; the Thread class for low-level threading control; and ThreadPool for effective resource management in the thread pool. These choices address various scenarios, enabling developers to select the best course of action in accordance with the demands of their application.

18. What do the C# terms “async” and “await” mean?


The C# keywords “async” and “await” are crucial for asynchronous programming. The term “await” is used inside a method to designate points at which execution can return control to the caller while awaiting the completion of an asynchronous operation. The “async” keyword is used to declare a method as asynchronous. This feature allows for the effective use of resources and enhances application responsiveness by preventing blocking.


  • public async Task MyAsyncMethod()
  • {
  • // Asynchronous code goes here
  • }


  • public async Task MyAsyncMethod()
  • {
  • // Asynchronous code before await
  • // Await an asynchronous operation
  • var result = await SomeAsyncMethod();
  • // Code after the awaited operation
  • }

19. Describe the idea of C# polymorphism.


In C#, objects of different types can be treated as objects of the same type thanks to polymorphism. Mechanisms like inheritance and interfaces help achieve this. A single interface, or base class, can define a set of common behaviours through polymorphism, and derived classes can offer particular implementations. This encourages the ability to write more generic and maintainable code as well as code reuse and flexibility.

20. What distinguishes “IQueryable” from “IEnumerable” in LINQ?



  • Ideal for performing queries on in-memory collections.
  • Executes client-side queries.
  • Gets every piece of information from the data source before filtering it.


  • Utilized for database queries.
  • carries out server-side query execution.
  • generates optimized queries by performing deferred execution.

21. What is the C# meaning of the keyword “sealed”?


In C#, the “sealed” keyword is used to stop a class from being further derived or a method from being overridden. It indicates that a class cannot be inherited when applied to it. It stops further overrides in derived classes when applied to a method. This limitation is helpful in cases where the design aims to complete specific elements, making sure that particular implementations or extensions are prohibited above a predetermined class hierarchy point.

22. Describe the function of the C# “yield” keyword.


In C#, iterator methods use the “yield” keyword to make the process of creating custom iterators easier. It enables the method to iteratively generate a series of values, pausing execution and giving the caller control back after each value is generated. Because the entire sequence doesn’t have to be generated at once, this makes it easier to write more readable and memory-efficient code when working with large datasets or complex computations.

23. What is the operation of the C# event handling mechanism?


The event handling mechanism in C# allows objects to communicate with each other through events. A class publishes events that other classes, referred to as subscribers, can sign up for. The publisher calls each subscribed subscriber’s event handler methods to notify them when an event happens. By separating the components, this encourages a flexible and modular architecture that allows various program components to react to particular events independently of one another.

24. What function does the “finally” block serve in handling exceptions?


  • Guarantees that the code specified is run whether or not an exception arises.
  • Perfect for carrying out cleanup tasks or resource releases.
  • Assures the completion of a step following the try and catch blocks.
  • Vital to preserving a stable state in extraordinary circumstances.

25. What is the C# keyword “volatile” used for?


  • shows that more than one thread may be modifying the same field.
  • makes sure that the field is not cached for reads or writes.
  • stops compiler optimizations that could remove or reorder accesses to volatile fields.
  • helpful in multithreaded scenarios to preserve data consistency for variables shared between threads.

26. What is the “Lambda” expression in C# server purpose?


A succinct way to write anonymous methods in C# is to use lambda expressions. To create delegates or implement functional interfaces, they provide a more condensed syntax. For LINQ queries, event handling, and other situations requiring a brief inline function, lambda expressions are frequently utilized. In particular, when the method logic is simple and doesn’t require a distinct named method, their conciseness and expressiveness make the code easier to read and maintain.

Lambda expression in C# server

27. Describe how to use the C# “ref” keyword.


When passing parameters to a method by reference in C#, use the “ref” keyword. Any modifications made to a parameter inside a method have an impact on the original variable outside the method when the parameter is passed by reference. This enables more dynamic and interactive programming, especially when a method needs to change a variable’s value and have that change reflected in the calling code.

28. What distinguishes “Deep Copy” from “Shallow Copy”?


Shallow copy:

  • makes a fresh object.
  • keeps allusions to the original’s underlying objects.
  • may result in mutual references.
  • Modifications made to shared objects affect the copy as well as the original.

Deep Copy:

  • makes a fresh object.
  • Duplicates the entire object graph recursively.
  • makes sure the copy and the original have no shared references.
  • eliminates unexpected dependencies by offering a fully independent copy.

29. Why are the C# “Checked” and “Unchecked” keywords there?


In integral-type arithmetic operations, overflow checking is managed by the C# “Checked” and “Unchecked” keywords. Overflow checking is enabled by the “Checked” keyword, which results in exceptions being thrown in the event of an overflow. The “Unchecked” keyword, on the other hand, prevents overflow checking, enabling arithmetic operations to continue without raising errors. These keywords provide flexibility in how arithmetic operations are handled depending on the particular needs of the application.

30. How is dependency injection implemented in C#, and what does it entail?


A design pattern called dependency injection (DI) aims to create loose coupling between software system components. Typically, constructor injection or method injection are used to implement DI in C#. Whereas method injection provides dependencies via method parameters, constructor injection provides dependencies as parameters to a class’s constructor. DI promotes flexibility and facilitates component replacement by enabling external dependency configuration, which improves code maintainability, testability, and scalability.

31. What does the C# “lock” statement?


In C#The “lock” statement is essential for handling situations involving multiple threads. It keeps race situations and data corruption in shared resources at bay by guaranteeing that a block of code is only executed by one thread at a time. Other threads are compelled to wait until the lock is released when a thread obtains the lock, giving it exclusive access to the code block. In concurrent programming, this synchronization mechanism is crucial to preserving data integrity and consistency.

32. The “Extension” methods in C# serve what purpose?


Without changing the source code of already-existing types, C#extension methods offer a way to add new methods. They cut down on the need to create derived types by allowing developers to increase the functionality of classes, interfaces, and structures. The purpose of extension methods is to modify the functionality of types from system assemblies or third-party libraries without changing the way they were implemented in the first place.

33. What distinguishes properties in C# from fields?



  • Give private fields restricted access.
  • Applied using the set and get methods.
  • Permit extra computations, validation, or logic to occur during access.
  • Enable the underlying data to be encapsulated.
  • Encourage a more regulated and flexible interface.


  • Keep data directly in a class.
  • usually private to keep implementation specifics contained.
  • Provide direct data access without the need for extra reasoning.
  • Not being able to impose restrictions while gaining access.

34. How do IDisposable objects and the “using” statement interact?


In C#, the “using” statement is specifically made for manipulating objects that have the IDisposable interface implemented. Declaring an object inside a “using” block guarantees that when the block is exited, either normally or as a result of an exception, the object’s Dispose method is automatically called.

35. What does the C# “throw” statement?


In a block of code, raising an exception manually is done with the “throw” statement in C#. By clearly indicating that an error has occurred, it enables developers to handle unusual circumstances or error scenarios. Exceptions allow programmers to control program flow and provide meaningful error messages in the event of unexpected situations. This helps with error handling and debugging.

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36. What is the C# implementation of the “Singleton” pattern?


In C#, a class is guaranteed to have a single instance and a global point of access through the Singleton pattern. Typically, a static instance variable is used to store the single instance and a private constructor is used to prevent external instantiation. To increase efficiency, the pattern frequently incorporates lazy initialization, which creates the instance only when it is first requested.

37. In C#, how does method overloading operate?


In C#, a class can define multiple methods with the same name but distinct parameters thanks to method overloading. It lets developers create variations of their methods that take varying kinds or counts of parameters, giving users flexibility in how they use them. Different parameter lists, with varying parameters in terms of quantity, kind, or order, are required for overloaded methods.

38. What is the performance difference between “String” and “StringBuilder”?



  • Unchangeable data format.
  • Changes result in new string objects.
  • Not suitable for large-scale concatenation.
  • StringBuilder:

  • changeable kind of data.
  • crafted to manipulate strings effectively.
  • alters the already-existing object.
  • increased efficiency for lengthy concatenation.

39. What are the In C# attributes?


In C#, attributes offer a way to give code elements metadata. They provide a means of adding extra information to annotate and enhance classes, methods, properties, and other elements. Tools, frameworks, or runtime environments can use this metadata to modify how the annotated elements behave or are configured. The `[AttributeName]} syntax is used to define attributes, which can be used for a number of tasks like validation, serialization, and creating custom code.

40. Describe the inversion of control (IoC) idea in C#.


The design principle known as Inversion of Control (IoC) involves inverting a system’s control flow. A higher-level framework or container gains control over the application’s flow instead of the individual components. In C#dependency injection, or DI, is a popular way to implement constructivity of dependencies (IoC). Instead of creating dependencies inside the class, DI injects them from outside the class. In the design of software systems, this encourages modularity, testability, and flexibility.

41. In C#, how can a thread-safe singleton pattern be put into practice?


To guarantee that only one instance of a class is created, particularly in multithreaded scenarios, it is imperative to implement a thread-safe singleton pattern in C#. Leveraging the `Lazy} class, which offers a thread-safe and effective way to implement lazy initialization, or employing strategies like double-check locking can accomplish this. Preventing race conditions and ensuring that a single instance is created and used correctly depend on thread safety.

42. What is the C# “as” operator used for?


In C#, safe type casting is accomplished with the “as” operator. If the cast cannot be completed, it returns null. It tries to cast an object to a given type. When the type of an object is unknown and you want to prevent exceptions that the standard cast operator might throw, this operator comes in handy. “as” is frequently used in situations where the outcome is uncertain because it offers a more accommodating method of handling type conversions.

43. What distinguishes “First” in LINQ from “FirstOrDefault”?



  • If no element that matches is found, an exception is thrown.
  • appropriate when a result is anticipated.
  • Perfect in situations where a match is assured.

First Or Default:

  • If no match is found, returns the element type’s default value.
  • offers a more secure choice for situations where matching elements might not be present.
  • helpful when it’s acceptable for there to be no match.

44. Regarding automatic properties, how is it handled by the C# compiler?


Without explicitly declaring the backing field, properties can be defined in C# using a succinct syntax thanks to automatic properties. Along with the standard getter and setter methods, the compiler automatically creates the backing field. Code readability is improved, boilerplate code is decreased, and property declaration is made simpler thanks to this feature.

45. Describe the function of the C# “volatile” keyword in relation to multithreading.


When referring to a field that can be updated by several threads in a multithreaded application, the C# the keyword “volatile” is utilized. This ensures that each thread reads and writes to the actual memory location rather than using cached values by preventing some compiler optimizations that might reorder or cache the variable. In situations where several threads access a shared variable, the “volatile” keyword is essential for preserving consistency and preventing unexpected behavior brought on by caching.

46. What distinguishes the “using” directive in C# from the “using” statement?


“Using” directive:

  • Utilized to add a namespace to the software.
  • Allows access to types in the namespace without requiring full qualification of their names.
  • Minimizes the need for fully qualified type names and improves the readability of code.

“Using” Statement:

  • Utilized in resource management, particularly in relation to IDisposable object disposal.
  • Assures that resources are properly cleaned up when they cross their scope.
  • Frequently employed in resource management to handle exceptions in conjunction with try-catch blocks.

47. Describe the C# concept of boxing and unpacking.


In C#, value and reference types are involved in the boxing and unboxing processes. The process of boxing entails changing a value type into a reference type so that it can be handled like an object. Conversely, unboxing is the process of returning a value type from a reference type. These operations serve as a bridge between the value-type and reference-type worlds in the C# programming language, and are essential when working with collections or interfaces that demand reference types.

48. What C# members are expression-bodied? Give an illustration.


In C#, members with expression bodies offer a simple syntax for defining methods, properties, and other members. The member is defined with a single expression as opposed to the conventional block syntax. A property could be defined like this, for instance: `public int DoubleValue => Value * 2; `For basic members in particular, this succinct syntax improves code readability and minimizes boilerplate.

49. In C# generics, talk about the concepts of covariance and contravariance.


Flexibility when working with types in a hierarchy is made possible by covariance in C# generics, which permits using a more derived type than was initially defined. The keyword “out” is used to accomplish it. Using the “in” keyword, however, achieves contravariance, which permits the use of a less derived type. With these ideas, generic types become more compatible and more versatile code can be written for a range of specificity levels.

50. What are the functions of the C# generic types’ “in” and “out” keywords?


“in” Keyword (Contravariance):

  • Permits the use of a generic type parameter as a contravariant type.
  • Allows the generic parameter to be assigned to more general types.
  • Increases adaptability by accepting a wider range of assignments.

“Out” Keyword (Covariance):

  • Enables generic types to be covariant.
  • Enables the generic parameter to be assigned to more specialized types.
  • Increases compatibility by allowing narrower, more derived type assignments.

51. What role does C#’s “Lazy<T>” class play in performance optimization?


In C#, the “Lazy<T>” class helps to optimize performance by holding off on creating an instance until it’s really needed. Lazy initialization helps minimize needless resource usage and enhances startup efficiency in situations where initializing an object could be expensive. The “Lazy” class effectively manages resources by delaying instantiation until the instance is first requested, particularly in situations where the creation of the object may be optional or infrequently required.

52. What does the “with” statement in C# do?


  • Creates immutable objects more easily.
  • Allows property changes while keeping the original instance.
  • Code readability is improved, and boilerplate code is reduced.
  • This is especially useful in scenarios where object properties are changed frequently.
  • Encourages the use of a clear and concise syntax for object modification.

53. How does the “record” type in C# make it easier to create immutable objects?


  • Immutable objects are defined in a concise manner.
  • Generates properties, equality methods, and a deconstructor automatically.
  • Boilerplate code associated with immutable object patterns is reduced.
  • Improves the readability and maintainability of code.
  • Ideal for situations where immutability is a design requirement.

54. What are channel and pipeline patterns in C#?


Channels and pipelines are C# design patterns for creating scalable and modular communication architectures. The channel pattern involves the exchange of messages between different components, promoting decoupling and independent communication. This pattern is frequently used in scenarios requiring efficient and asynchronous communication.

55. Explain the significance of “Covariant Returns” in C#.


  • Allows for the replacement of a base class method with a more derived return type.
  • Increases the flexibility with which class hierarchies can be designed.
  • Increases the expressiveness of the code by returning more specific types in derived classes.
  • Improves integration with polymorphic behavior.
  • Useful in situations where a more specialized result in derived classes is expected.

56. What role does the “Span<T>” type play in improving memory efficiency in C#?


“Span<T>” is a lightweight type in C# that represents a contiguous region of memory, contributing to improved memory efficiency. This type is intended for efficient data manipulation without the need for redundant copying. It is especially useful in scenarios requiring high-performance data processing, as it supports operations like slicing, indexing, and direct memory manipulation.

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57. Discuss the advantages and disadvantages of asynchronous programming in C#.



  • Increases the scalability and responsiveness of the system.
  • Allows for non-blocking execution, which improves overall performance.
  • Allows for parallelism and efficient resource use.


  • Deadlocks and race conditions could be introduced.
  • Because of the asynchronous nature, code complexity has increased.
  • Debugging and error handling may become more difficult.

58. What role does the “CallerMemberName” attribute play in C# programming?


  • Logging and debugging tasks are made easier.
  • The name of the calling member is automatically provided.
  • It eliminates the need to explicitly pass member names as arguments.
  • Reduces the number of hardcoded member names, which improves code maintainability.
  • Useful in scenarios requiring dynamic or runtime information about the calling member.

59. Describe “pattern matching” in C# terms.


C#’s pattern matching feature makes code simpler by offering more concise and expressive methods for checking types and extracting information from objects. It has features like “switch” expressions for handling multiple cases based on patterns and “is” expressions for type checking. This feature makes code more readable by enabling developers to more succinctly express their intentions; it is especially helpful in situations where conditional logic entails intricate object deconstruction or type checks.

60. What does the “in” modifier in the method parameters of a C# code mean?


  • Signifies that a parameter is read-only inside the method but is passed by reference.
  • Enhances performance by preventing needless duplication of complicated or big structures.
  • Helpful when a procedure needs read-only access to a parameter so that it cannot be changed.

61. Differences Between “ValueTuple” and Traditional “Tuple” in C#:



  • ValueTuple is a lightweight value-type replacement.
  • A reference type is Classic Tuple.


  • ValueTuple does not use heap allocations.
  • Heap allocations are used in classic Tuple.


  • Because it avoids heap allocations, ValueTuple is more efficient.
  • Due to heap allocations, Classic Tuple may incur performance overhead.

62. Provide an example of “C# Interpolated Strings” and explain the concept.


C# Interpolated Strings allow you to embed expressions directly into string literals, improving readability and expressiveness. $”The sum is a + b” is an example of an interpolated string. The expressions contained within the curly braces in this example are evaluated and seamlessly integrated into the resulting string, simplifying string formatting and concatenation.

63. Discuss the advantages of using the “MemoryCache” class in C# for data caching.


In C#, the “MemoryCache” class provides a simple and efficient in-memory caching mechanism that contributes to improved application performance. Repetitive computations or data retrievals can be avoided by caching data in memory, reducing the overall workload on the application and improving response times.

64. Discuss the use of “Memory” in C# and its advantages.


“Memory” Usage:

  • It allows you to work with contiguous memory blocks.
  • Allows for efficient data manipulation while avoiding unnecessary allocations.
  • This is especially useful in scenarios involving large datasets or stream processing.


  • Reduces memory allocations by allowing the reuse of memory blocks.
  • Increases performance by avoiding unnecessary data copying.
  • Suitable for scenarios requiring fine-grained memory control.

65. How does C#’s “ref readonly” feature improve performance?


In C#, the “ref readonly” feature allows the passing of a value type by reference while preventing modifications. This feature improves performance by eliminating the need for unnecessary value type copying. When dealing with large value types, avoiding unnecessary copies becomes critical for optimizing performance, making “ref readonly” a useful feature in scenarios requiring both pass-by-reference semantics and readonly constraints.

66. What are the “in” and “ref” keywords in C# 7.x and later versions for?


The keyword “in”

  • Used for read-only reference parameters.
  • This value indicates that the parameter was passed by reference.
  • Modifications to the parameter are not permitted within the method.

“ref” is a keyword.

  • For use with writable reference parameters.
  • This value indicates that the parameter was passed by reference.
  • Allows for parameter changes within the method.
  • Allows values to be passed by reference for both reading and writing.

67. Explain what “C# Local Functions” are and when they are useful.


In C#, local functions are functions that are declared within another function, providing encapsulation and reducing code complexity. They are useful for code organization in a limited context. Local Functions improve readability by grouping related logic together, encourage encapsulation by limiting visibility, and contribute to cleaner code structure.

68. Discuss the role of “Default Interface Methods” in C# and how they affect compatibility.


Default Interface Methods in C# are critical in the evolution of interfaces over time. They make it possible to add new methods to interfaces without breaking existing implementations. This feature improves backward compatibility by allowing classes that implement an interface with a default method to continue to function without modification.

69. In C#, what are “Attributes” and how are they used for metadata?


In C#, attributes are metadata tags that provide extra information about code elements. They are used in code to add metadata or behavior. Attributes can be applied to different elements such as classes, methods, or properties to influence their behavior or provide information to tools and compilers. Serialization attributes, which control how objects are serialized, and compiler directives, which guide compilation processes, are two examples.

70. Explain the concept of “C# Indexers” and give an example of how they are used.


C# indexers enable objects to be indexed like arrays, allowing access to elements via square bracket notation. An indexer is an example:

  • public class MyCollection
  • {
  • private int[] array = new int[10];
  • public int this[int index]
  • {
  • get => array[index];
  • set => array[index] = value;
  • } }

In this example, the MyCollection class includes an indexer that allows direct access to array elements. Indexers improve the usability and syntax of classes by making them behave similarly to arrays when accessing elements.

71. What role does the “Memory Pool” pattern play in memory efficiency in C#?


The Memory Pool pattern in C# entails reusing previously allocated chunks of memory to reduce memory fragmentation and allocation overhead, resulting in improved performance. This pattern reduces the chances of memory fragmentation by recycling memory rather than constantly allocating and deallocating, which can lead to more efficient memory use.

72. What is the purpose of the “Stackalloc” keyword in C#?


The “stackalloc” keyword in C# is used to allocate memory on the stack, providing a quick but limited way to allocate memory for temporary buffers. It is especially useful when a short-lived memory buffer is required and the performance benefits of stack allocation outweigh the limitations associated with the size and lifespan of the allocated memory.

73. Discuss the distinctions between “Asynchronous Streams” and “Synchronous Streams” in C#.


Asynchronous Streams:

  • Enable asynchronous sequence production and consumption.
  • Appropriate for asynchronous data handling.
  • Supports asynchronous operations, which improves responsiveness.

Synchronous Streams:

  • Simpler, but it prevents calling code from being executed until the entire sequence is completed.
  • It is necessary to wait for each element to be produced before processing.
  • Because of the blocking, resource utilization may be less efficient.

74. What is the “Pipeline” pattern and how does it improve code modularity and scalability in C#?


The Pipeline pattern in C# entails breaking complex processes down into a series of stages or steps, which contributes to improved code modularity and scalability. The pipeline’s stages each perform a specific task, and the output of one stage becomes the input for the next. This pattern improves code organization, allows for parallel or sequential execution, and makes maintenance easier.

75. What are “Anonymous Types” in C#, and when do they come in handy?


Anonymous Types in C# enable the dynamic definition of types without explicitly declaring a class. They come in handy when dealing with temporary data structures or when the type is only known at runtime. Anonymous Types provide a concise syntax for creating objects on the fly, often simplifying code in situations where the data structure is straightforward and a full-fledged class definition would be considered excessive.

76. What distinguishes “C# Local Static Functions” from regular local functions?


Local Static Functions in C#:

  • Common to all instances of a class.
  • Located in a single memory location.
  • When the logic is the same for all instances, provide performance benefits.

Ordinary Local Functions:

  • Affixed to each instance of a class.
  • Tied to the state of the specific instance.
  • Suitable for situations in which function behavior varies by instance.

77. What does the C# “in” keyword mean when it comes to read-only structs?


  • Used as a method parameter with read-only structs.
  • Shows passing without alteration by reference.
  • Improves efficiency and prevents needless duplication.
  • Especially helpful for sizable read-only structures.
  • Guarantees effective management of struct instances.

78. Talk about the benefits and difficulties of utilizing “Expression Trees” in C#.



  • Permit code to be represented as data structures.
  • Provide robust scenarios such as query translation for LINQ.


  • Trees are complicated to understand and build.
  • Possible effect of the extra abstraction on performance.

79. In C# asynchronous programming, how does the “CancellationToken” help with effective cancellation?


  • Permits asynchronous operations to be canceled cooperatively.
  • Improves resource management and responsiveness.
  • Allows for clean cancellation without interrupting the thread.
  • Works well with a variety of asynchronous patterns.
  • Enables asynchronous task termination with grace.

80. What are the effects on expressiveness and code safety of the “C# Nullable Reference Types” feature?


Introduced in C# 8, C# Nullable Reference Types have a significant effect on both code safety and expressiveness. The feature reduces runtime errors related to null and improves code safety by explicitly defining nullable reference types. When there are possible nullability problems, the compiler alerts developers and tightens up null handling. This helps with expressiveness as well as code robustness by enabling developers to express their intentions about nullability clearly.

81. Describe the idea of “C# Attributes” and how code annotations and behaviour’s use them.


  • Used to give code elements additional behaviour or metadata.
  • You can alter runtime or compilation behaviour by annotating code.
  • Improve documentation and code readability.
  • Enable attribute-based conditional compilation.
  • Frequently used for diagnostics and code generation.

82. How does C#’s “Tail Call Optimization” affect recursion and what does it mean?


  • Optimization method that lowers the amount of stack space used by recursive calls.
  • Stops stack overflow when using tail-recursive functions in specific situations.
  • Makes it possible to manage memory during recursion more effectively.
  • Crucial for managing recursive deep algorithms.
  • Supported in particular tail-recursive patterns by the C# compiler.
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83. Discuss the advantages things to think about when utilizing “Value References” in C#.


Performance Enhancement:

  • The use of mutable structs with reference semantics is made possible by value references.
  • Reduce superfluous struct instance copying to increase performance.

Efficiency of Memory:

  • By avoiding unnecessary struct allocations, you can lower memory overhead.
  • Allow for more effective memory management in situations where struct modifications occur frequently.

Reference Semantics Simulated:

  • Give value types an interface to be used like reference types.
  • Permit changes to be made to the original struct instance by using the reference.

84. What function does the C# programming language’s “CallerLineNumber” attribute serve?


  • Gives the calling code’s line number.
  • Improves information for debugging and logging.
  • Makes it easier to pinpoint the exact location of the source.
  • Useful for thorough troubleshooting and error tracking.
  • Enhances problem-solving and code maintenance.

85. Describe “C# Stackalloc Arrays” and the scenarios in which they are used.


  • Set aside memory for temporary buffers on the stack.
  • Allocate memory quickly but in moderation.
  • Ideal for compact and transient arrays.
  • Effective in situations where stack memory is adequate.
  • Used in some circumstances to avoid heap allocation overhead.
  • Frequently used in code sections where performance is a concern.

86.For asynchronous programming in C#, what does the “IValueTaskSource” interface mean?


Developers can personalize the creation and management of tasks with the help of the IValueTaskSource interface in C# asynchronous programming. By giving users the option to customize the creation and completion of tasks, this interface facilitates more precise control over the asynchronous workflow. If the default task creation and management mechanisms aren’t working well in a given scenario, developers can use this interface to customize task behavior according to specific requirements.

87. What ways does the “C# IAsyncEnumerable” involving asynchronous streaming?


  • Asynchronous creation and consumption are made possible by “IAsyncEnumerable”.
  • Makes handling asynchronous sequences more effective.
  • Enhances scalability in situations where asynchronous streams are present.
  • Allows for responsive applications to support asynchronous operations.
  • Enables the use of well-known patterns to work with asynchronous streams by developers.

88. Talk about the function of “C# Unsafe Code” and its possible applications.


  • Allows pointer arithmetic and direct memory manipulation.
  • Required for scenarios requiring low-level control and where performance is critical.
  • should be used cautiously because of possible security vulnerabilities.
  • Permits getting around some of the managed code’s safety measures.
  • Frequently used in certain situations, such as low-level data processing or high-performance graphics.

89. How does C#’s “Strongly Typed Reflection” feature vary from conventional reflection methods?


Summary of Features:

  • Enables reflection operations to be validated at compile time.
  • Improves type safety and performance.
  • First appeared in C# 9 to address the drawbacks of conventional reflection.

Distinctions from Conventional Reflection:

  • At compile time, reflection operations are verified.
  • By enforcing type safety, runtime errors are decreased.
  • Increases code maintainability and developer experience.

90. Describe the idea of C# “Code Contracts” and how they help to increase code reliability.


Formally defined specification:

  • Declare in code the preconditions, postconditions, and invariants.
  • Specify the parameters that will govern the behavior of the method.

Enhancing Code Dependability:

  • Reliability is increased by runtime code contract checks.
  • During development, find and fix contract violations.
  • Help write code that is more reliable and consistent.

91. Discuss the advantages and disadvantages of utilizing “C# Source Generators” in code generation.



  • Code can be generated during compilation to enhance efficiency.
  • Minimize the overhead of reflection during runtime.
  • Increase the maintainability of your code by automating tedious tasks.


  • Add more intricacy to the process of development.
  • Learning curve for source generator comprehension and application.
  • Needs to be carefully considered for the right use cases.

92. Give instances of how to use “C# Pattern Matching” in your response.


  • Type-Pattern Switch Statements: Type-safe branching can be achieved in switch statements by using the “is” keyword to determine whether an object matches a particular type pattern.
  • Switch Expressions: New in C# 8, switch expressions allow for pattern-based matching that is both expressive and succinct, enhancing readability and cutting down on boilerplate code.
  • Case Statement Pattern Matching: By using patterns directly in case statements, more dynamic and type-aware conditions can be used in place of constant values.

93. What does “PipelineBuilder” do for C# pipelines, and what are the benefit of it?


The “PipelineBuilder” in C# is designed to make pipeline construction easier by utilizing a fluid and modular syntax. It makes the construction of intricate processing pipelines by developers easier to understand and more organized. The PipelineBuilder’s fluid interface allows processing steps to be added one after the other, increasing the code’s expressiveness and modularity. The ease with which each pipeline step can be extended, changed, or configured encourages code maintainability and flexibility.

94. In C# asynchronous, differentiate between value task and task.



  • ValueTask is a value type that can represent both synchronous and asynchronous results.
  • Optimized for scenarios where unnecessary allocations can be avoided.
  • Efficiency: Lightweight asynchronous operations are more efficient.


  • Task is a reference type that represents an asynchronous operation.
  • Generally used for a variety of asynchronous tasks.
  • Allocation: More allocations may be required, potentially affecting performance.
  • Overhead: Task may have more overhead than ValueTask.

95. Describe the C# serialization concept.


  • Objects can be serialized to create a stream of bytes for transmission or storage.
  • Enables data transfer between various platforms or the preservation of object state.
  • Frequently used when sending objects over networks or storing object state in files or databases.
  • XML and binary serialization are frequently used C# techniques.

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