Top 50 C# Interview Questions and Answers
10/Oct/2020 | 15 minutes to read
Here is a List of essential C# Interview Questions and Answers for Freshers and mid level of Experienced Professionals. All answers for these C# questions are explained in a simple and easiest way. These questions will help you to clear your next Job interview.
C# Interview Questions and Answers
These interview questions are targeted for C# Programming language. A .NET Developer should know the answers of these C# questions to clear the interview.
1. What is latest version of C# with features?
C# 1.0 released in 2002. And latest version of C# is 9.0. For more you can visit Microsoft official site Releases . There are many new features in C# 9.0. For more you can visit What's new in C# 9.0.
2. What is the difference between const, readonly and static keyword?
3. What is the difference between in, ref and out keywords?
4. What is the Inheritance? Why C# does not support multiple Inheritance?
5. What is method shadowing or method hiding in C#?
6. Differentiate Var, Object and Dynamic keywords in C#.
7. Can Virtual or Abstract member be declare private in C#?
No, It will throw compile time error.
virtual void display() // will throw error here
{
// Implementation
}
8. What is Boxing and Unboxing in C# ?
9. What is Method Overloading in C#?
10. What is Value Type and Reference Type in C#?
10. What are the new features in C# 8.0?
To know more about C# 8.0 new features visit What's new in C# 8.0
11. What is Abstraction and Encapsulation in C#? How will you differentiate them?
12. What is the deference between Abstract class and Interface in C#? What is the need of these?
13. What is Polymorphism? What is static and Dynamic Polymorphism in C#?
14. What will be output of below program? Error Line will throw any error in below code?
class A
{
public virtual void display()
{ Console.WriteLine("A - display method"); }
}
class B:A
{
public override void display()
{ Console.WriteLine("B - display method"); }
}
class Test
{
static void Main()
{
A obj = new A();
obj.display();
A obj1 = new B();
obj1.display();
B o = new B();
o.display();
// B ob = new A(); Error Line
Console.ReadLine();
}
}
Output: 'Error Line' will throw error - Cannot implicitly convert type 'A' to 'B'. An explicit conversion exists (are you missing a cast?).
Output will be as below.
A - display method
B - display method
B - display method
16. Can Abstract class has constructor in C#? Below code will compile or not, or it will give any error in Error line 1 or 2.
class A
{
public virtual void display()
{
Console.WriteLine("A - display");
}
public virtual void disp()
{
Console.WriteLine("A - disp");
}
}
abstract class ab :A
{
public ab()
{ }
public abstract override void display(); Error Line 1
public sealed override void disp() Error Line 2
{
Console.WriteLine("disp is sealed now.");
}
}
Solution: Abstract class can contain the constructor. Constructor is used to instantiate the class instance members in C#.
Above code will compile successfully. In C#, we can add Abstract and Sealed keywords with the override keyword.
17. What is volatile keyword in C#?
18. What is the use of sealed keyword in C#?
19. Explain string interpolation in C#.
20. What is the difference between abstract and virtual keywords?
20. What are the new features in C# 7.0?
To know more about C# 7.0 new features visit What's new in C# 7.3
21. What is Covariance and Contravariance in C#?
Fore more Covariance and Contravariance in C#
22. What will be output of following program? or will throw any error?
public void display()
{
int x = 0;
int y = 10;
try
{
int z = y / x;
}
catch (Exception)
{
throw;
}
catch (DivideByZeroException)
{
throw;
}
finally
{
}
}
23. What points (related to try, catch and finally) you should keep in mind while implementing exception handling in C#?
24. What is Generics in C#? What are the benefits of Generics?
25. What is IDisposable Interface in C#? How to implement dispose method?
26. Explain Dispose Pattern in C#.
27. How does Garbage Collection work in C#? Explain Generations.
28. What is using statement in C#?
29. What is Finalizers in C#? Explain SupressFinalize() method.
30. What will be output of below code?
int a = 0;
try
{
int x = 4;
int y ;
try
{
y = x / a;
}
catch (Exception e)
{
Console.WriteLine("inner ex");
//throw; // Line 1
//throw e; // Line 2
//throw new Exception("divide by 0"); // Line 3
}
}
catch (Exception ex)
{
Console.WriteLine("outer ex");
throw ex;
}
31. What is Equals method?
32. What is the difference between Equality operator == and Equals() method in C#?
33. What is the use of new keyword rather than creating new object in C#?
34. What is the extension methods in C#?
35. Explain Partial class and methods.
36. In how many ways can you pass parameters in C#?
37. What is the difference between EXE and DLL file?
38. What is DLL hell Problem?
39. What is Asynchronous Programming?
40. What is async and await in C#?
44. What are the new features in C# 6.0?
To know more about C# 6.0 new features visit What's new in C# 6.0
Some General Interview Questions for C#
1. How much will you rate your self in C#?
When you attend an interview, Interviewer may ask you to rate your self in specific Technology like C#, So It's depend on your knowledge and work experience in C#.
2. What challenges did you face while working on C#?
This question may be specific to your technology and completely depends on your past work experience. So you need to just explain the challenges you faced related to C# in your Project.
3. What was your role in last Project related to C#?
It's based on your role and responsibilities assigned to you and what functionality you implemented using C# in your project. This question is generally asked in every interview.
4. How much experience do you have in C#?
Here you can tell about your overall work experience on C#.
5. Have you done any C# Certification or Training?
It's depend on candidate like you have done any C# training or certification. Certifications or trainings are not essential but good to have.
Conclusion
We have covered some frequently asked C# Interview Questions and Answers to help you for your Interview. All these Essential C# Interview Questions are targeted for mid level of experienced Professionals and freshers.
While attending any C# Interview if you face any difficulty to answer any question please write to us at info@qfles.com. Our IT Expert team will find the best answer and will update on portal. In case if we find any new C# questions, we will update the same here.