C# Interview Questions and Answers
C#, sometimes also called as C sharp, is a component-oriented, general-purpose computer programming language that encompasses strong typing, declarative, imperative, and object-oriented disciplines. This information has been asked quite a few times recently in C# interview questions. It is a multi-paradigm language that was initially designed for Common Language Infrastructure (CLI).
C# allows the developers to build reusable components for a huge variety of applications. C# is an evolution or extension of C and C++ languages. However, it has taken much of its features from other programming languages as well, including Delphi and Java. When you analyze the basic syntax of C# and Java and C++, it will look very similar, which is intentional and not a coincidence.
Most Frequently Asked C# Interview Questions
Here in this article, we will be listing frequently asked C# Interview Questions and Answers with the belief that they will be helpful for you to gain higher marks. Also, to let you know that this article has been written under the guidance of industry professionals and covered all the current competencies.
C sharp is a component-oriented, general-purpose computer programming language that encompasses strong typing, declarative, imperative, and object-oriented disciplines. It is a multi-paradigm language that was initially designed for Common Language Infrastructure (CLI)
Why It is used for?
You can write desktop applications, Console applications, ASP.NET applications, and scalable cloud apps. These are only a few of the uses of C#; a skilled developer can do a lot more than this.
Some of the features of C# include:
- Properties
- Indexers
- Constructors and Destructors
- Arrays
- XML Documentation
- Passing Parameters
- Main
It was developed by Microsoft around the year 2000.
| S.no | C# | .NET |
|---|---|---|
| 1. | Programming language | Framework on which the language is built |
| 2. | Runs on the .NET framework | Primarily runs on Windows |
| 3. | One of the many languages in the .NET Framework | Includes various languages under it |
The term "sharp" is inspired by music notation that indicates that the musical note should be higher in pitch. This has been applied to the language C++, where "++" indicates that its performance will ideally be improved or increased by 1. The sharp symbol resembles four "+" symbols (in a grid of two-by-two), that may imply to some that C# is an advanced or improved version of C++. We have the most extensive question bank to help you answer C# interview questions.
Winforms, or Windows Forms, are a graphical user interface or application programming interface (API) that are included in Microsoft's .NET Framework.
- Easy to understand
- Object and component-oriented
- Faster and safer
- Part of Microsoft's .NET framework
An Interface in C# is an abstract class that has no implementation and contains abstract public methods. These methods have a declaration and not a definition, and are implemented in inherited classes.
In C#, the different types of classes are Partial class, Sealed class, Abstract class, and Static class.
| S.no | Dynamic type variables | Object type variables |
|---|---|---|
| 1. | Introduced in C# 4.0 | Introduced in C# 1.0 |
| 2. | Handle-type checking at runtime | Handle type checking at compile time |
| 3. | Casting not required | Cast object variables to original types |
This information is usually asked in C# technical interview questions. In C#, there are mainly three kinds of comments - single line, multiple lines, and XML comments.
| S.no | Constant variables | Read-only variables |
|---|---|---|
| 1. | Declared at compile time | Used to assign a value at run time |
| 2. | Value cannot be changed | Value can be changed |
| S.no | finally | finalize |
|---|---|---|
| 1. | Called after execution of block | Called before garbage collection |
| 2. | Used for exception handling. | Used for performing clean up operations |
| 3. | Usually contains clean-up code | Automatically called when an instance is not called subsequently. |
Programming errors in C# are mainly of three types - Syntax Errors, Run time Errors, and Logic Errors.
This information can be asked during C# interview questions and answers.
| S.no | Public | Static | Void |
|---|---|---|---|
| 1. | An access modifier | A type modifier | |
| 2. | Declared variables are accessible from anywhere | Declared variables are globally accessible | Variable does not return value |
A jagged array, also called an Array of arrays, contains different elements of a type array. The elements in a jagged array can be of different dimensions and sizes.
Value types in C# are stored in a Stack. For example, int, byte, double.
Reference types in C# are stored on a heap. For example, string, interface.
A constructor in C# is a member function of a class that contains the same name as its parent class. This function gets automatically invoked when an object class gets created. A constructor constructs values in data members while initializing the parent class.
There are five types of constructors - Static constructor, Private constructor, Copy constructor, Default constructor, and Parameterized constructor.
The access modifiers usually used in C# include Public, Private, Protected, Internal and Protected internal.
This is one of the frequently asked C# interview questions.
| S.no | Struct | Classes |
|---|---|---|
| 1. | Value-type | Reference types |
| 2. | Inheritance not supported | Inheritance supported |
| 3. | Members public by default | Members private by default |
This class is used for creating classes or objects that do not contain a specific data type. This kind of data type is assigned during the runtime.
It is a collection of keys or value pairs that contains values based on keys.
Converting a specific value type to a particular reference type is known as Boxing.
Whereas, explicit conversion of same reference types, that were created during boxing, back to the same value type is known as Unboxing.
Polymorphism refers to the same method that gives different implementations. In C#, Polymorphism is of two types - Compile-time and Runtime.
StreamReader and StreamWriter are two different classes in namespace System.IO. Both of these classes are used when the user wants to read or write charact90 and Reader-based data, respectively.
Members of StreamReader inlcude, Close(), Read(), Readline().
Members of StreamWriter include, Close(), Write(), Writeline().
This is an essential topic in C# interview questions for experienced professionals. Some of the basic string operations in C# are Concatenate, Modify, Compare and Search.
A Delegate in C# is a variable, which holds a reference to a specific method. This also makes a delegate a function pointer of a reference type. All the Delegates are derived from the System. Delegate namespace.
Delegates are of three types -
- Single Delegate
- Multicast Delegate
- Generic Delegate
Synchronous is one of the ways to create a thread-safe code in C# where only one thread is able to access resources at any time.
Asynchronous call waits for a method to get completed before continuing with program flow. In an Asynchronous operation, the method call immediately returns so that the program can perform operations while the called method finished its task.
| S.no | System.Array.Clone() | System.Array.CopyTo() |
|---|---|---|
| 1. | Used for creating a new array containing elements of the original array | Elements of existing array get copied into another existing array. |
| 2. | Does not require a destination array to exist | Destination array must exist |
"is" operator
- Used to check compatibility of the object with a given type
- Returns result as Boolean.
"as" operator
- Used for the casting of the object to type or class
Hiring managers will be impressed if you have this information during C# interview questions. A Thread in C# is a set of guidelines or instructions that are executed, and enable the program to do concurrent processing. The concurrent processing of a program helps the developers handle more than one operation at a given time.
The different states of thread are listed below-
- Unstarted
- Running
- WaitSleepJoin
- Suspended
- Aborted
- Stopped
In C#, there is a special data type called the nullable types. To this data type, the developers can assign a normal range of values as well as null range of values.
In C#, you can sort an array using the Using Array.sort(array) function. This function will sort the elements in the entire one-dimensional Array using IComparable implementation for each element of the given Array.
In C#, Stack is used during the static memory allocation. The variables that are allocated on the stack are stored directly in memory and access to this memory is fast. Heap is used during the dynamic memory allocation. The variables that are allocated on heap have memory allocated during runtime and access to this memory is slow.
Note: If you are preparing for a C# interview, you can read our C# technical interview questions for in-depth knowledge.