Technical interview questions and answers help you perform well in any C# Interview because companies test your understanding of .NET concepts, OOPs, collections, delegates, LINQ, and error handling. C# is widely used in enterprise applications, making it a key skill for software development roles. Companies like TCS, Wipro, Infosys, Cognizant, and Capgemini frequently ask core C# questions to evaluate your coding skills and understanding of the .NET ecosystem. This guide includes commonly asked C# interview questions with detailed explanations to help freshers and job seekers strengthen their technical foundation. These questions will support your preparation for coding rounds, technical interviews, and project-related discussions.
C# developers can expand their Microsoft technology stack by learning .NET framework architecture and Windows programming techniques
2. Are private class-level variables inherited?
Answer: Yes, but they are not accessible, so looking at it you can honestly say that they are not inherited. But they are.
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3. C# provides a default constructor for me. I write a constructor that takes a string as a parameter, but want to keep the no parameter one. How many constructors should I write?
Answer: Two. Once you write at least one constructor, C# cancels the freebie constructor, and now you have to write one yourself, even if there
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4. Can multiple catch blocks be executed?
Answer: No, once the proper catch code fires off, the control is transferred to the finally block (if there are any), and then whatever follows the finally block.
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5. Can you allow class to be inherited, but prevent the method from being over-ridden?
Answer: Yes, just leave the class public and make the method sealed.
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6. Can you change the value of a variable while debugging a C# application?
Answer: Yes, if you are debugging via Visual Studio.NET, just go to Immediate window.
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7. Can you declare the override method static while the original method is non-static?
Answer: No, you can
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9. Can you override private virtual methods?
Answer: No, moreover, you cannot access private methods in inherited classes, have to be protected in the base class to allow any sort of access.
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10. Can you prevent your class from being inherited and becoming a base class for some other classes?
Answer: Yes, that
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14. How can you overload a method?
Answer: Different parameter data types, different number of parameters, different order of parameters.
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15. How can you sort the elements of the array in descending order?
Answer: By calling Sort() and then Reverse() methods.
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16. How do you debug an ASP.NET Web application?
Answer: Attach the aspnet_wp.exe process to the DbgClr debugger.
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17. How do you generate documentation from the C# file commented properly with a command-line compiler?
Answer: Compile it with a /doc switch.
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18. How do you inherit from a class in C#?
Answer: Place a colon and then the name of the base class. Notice that it
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19. How
Answer: When overriding, you change the method behavior for a derived class. Overloading simply involves having a method with the same name within the class.
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20. How
Answer: Assembly versioning allows the application to specify not only the library it needs to run (which was available under Win32), but also the version of the assembly.
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21. If a base class has a bunch of overloaded constructors, and an inherited class has another bunch of overloaded constructors, can you enforce a call from an inherited constructor to an arbitrary base constructor?
Answer: Yes, just place a colon, and then keyword base (parameter list to invoke the appropriate constructor) in the overloaded constructor definition inside the inherited class.
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23. What are advantages and disadvantages of Microsoft-provided data provider classes in ADO.NET?
Answer: SQLServer.NET data provider is high-speed and robust, but requires SQL Server license purchased from Microsoft. OLE-DB.NET is universal for accessing other sources, like Oracle, DB2, Microsoft Access and Informix, but it
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24. What are the ways to deploy an assembly?
Answer: An MSI installer, a CAB archive, and XCOPY command.
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25. What are three test cases you should go through in unit testing?
Answer: Positive test cases (correct data, correct output), negative test cases (broken or missing data, proper handling), exception test cases (exceptions are thrown and caught properly).
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26. What connections does Microsoft SQL Server support?
Answer: Windows Authentication (via Active Directory) and SQL Server authentication (via Microsoft SQL Server username and passwords).
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28. What does assert() do?
Answer: In debug compilation, assert takes in a Boolean condition as a parameter, and shows the error dialog if the condition is false. The program proceeds without any interruption if the condition is true.
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29. What does Dispose method do with the connection object?
Answer: Deletes it from the memory.
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30. What does the keyword virtual mean in the method definition?
Answer: The method can be over-ridden.
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31. What does the parameter Initial Catalog define inside Connection String?
Answer: The database name to connect to.
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32. What does the This window show in the debugger?
Answer: It points to the object that
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33. What is a pre-requisite for connection pooling?
Answer: Multiple processes must agree that they will share the same connection, where every parameter is the same, including the security settings.
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35. What namespaces are necessary to create a localized application?
Answer: System.Globalization, System.Resources.
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36. What
Answer: A delegate object encapsulates a reference to a method. In C++ they were referred to as function pointers.
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38. What
Answer: When you write a multilingual or multi-cultural application in .NET, and want to distribute the core application separately from the localized modules, the localized assemblies that modify the core application are called satellite assemblies.
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39. What
Answer: A class that cannot be instantiated. A concept in C++ known as pure virtual method. A class that must be inherited and have the methods over-ridden. Essentially, it
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43. What
Answer: StringBuilder is more efficient in the cases, where a lot of manipulation is done to the text. Strings are immutable, so each time it
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44. What
Answer: A catch block that catches the exception of type System.Exception. You can also omit the parameter data type in this case and just write catch {}.
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47. What
Answer: In the interface all methods must be abstract; in the abstract class some methods can be concrete. In the interface no accessibility modifiers are allowed, which is ok in abstract classes.
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48. What
Answer: System.String is immutable; System.StringBuilder was designed with the purpose of having a mutable string where a variety of operations can be performed.
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49. What
Answer: Documentation looks the same. Use Debug class for debug builds, use Trace class for both debug and release builds.
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50. What
Answer: The first one performs a deep copy of the array, the second one is shallow.
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52. What
Answer: It returns a read-only dataset from the data source when the command is executed.
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54. When do you absolutely have to declare a class as abstract (as opposed to free-willed educated choice or decision based on UML diagram)?
Answer: When at least one of the methods in the class is abstract. When the class itself is inherited from an abstract class, but not all base abstract methods have been over-ridden.
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55. When you inherit a protected class-level variable, who is it available to?
Answer: Classes in the same namespace.
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56. Where is the output of TextWriterTraceListener redirected?
Answer: To the Console or a text file depending on the parameter passed to the constructor.
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57. Which one is trusted and which one is untrusted?
Answer: Windows Authentication is trusted because the username and password are checked with the Active Directory, the SQL Server authentication is untrusted, since SQL Server is the only verifier participating in the transaction.
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58. Why are there five tracing levels in System.Diagnostics.TraceSwitcher?
Answer: The tracing dumps can be quite verbose and for some applications that are constantly running you run the risk of overloading the machine and the hard drive there. Five levels range from None to Verbose, allowing to fine-tune the tracing activities.
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59. Why can
Answer: They all must be public. Therefore, to prevent you from getting the false impression that you have any freedom of choice, you are not allowed to specify any accessibility, it
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60. Why is it a bad idea to throw your own exceptions?
Answer: Well, if at that point you know that an error has occurred, then why not write the proper code to handle that error instead of passing a new Exception object to the catch block? Throwing your own exceptions signifies some design flaws in the project.
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61. Why would you use untrusted verificaion?
Answer: Web Services might use it, as well as non-Windows applications.
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