C Sharp Interview Questions and Answers

1. What’s the advantage of using System.Text.StringBuilder over System.String?

Ans : StringBuilder is more efficient in the cases, where a lot of manipulation is done to the text. Strings are immutable, so each time it’s being operated on, a new instance is created.

2. What’s the C# equivalent of C++ catch (…), which was a catch-all statement for any possible exception?

Ans : 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 {}.

3. Can multiple catch blocks be executed?

Ans : 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.

4. Why is it a bad idea to throw your own exceptions?

Ans : 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.

5. How’s the DLL Hell problem solved in .NET?

Ans : 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.

6. What’s a satellite assembly?

Ans : 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.

7. What debugging tools come with the .NET SDK?

Ans : CorDBG – command-line debugger, and DbgCLR – graphic debugger. Visual Studio .NET uses the DbgCLR. To use CorDbg, you must compile the original C# file using the /debug switch.

8. What does assert() do?

Ans : 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.

9. Why are there five tracing levels in System.Diagnostics.TraceSwitcher?

Ans : 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.

10. What are three test cases you should go through in unit testing?

Ans : 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).

11. What are advantages and disadvantages of Microsoft-provided data provider classes in ADO.NET?

Ans : 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’s a .NET layer on top of OLE layer, so not the fastest thing in the world. ODBC.NET is a deprecated layer provided for backward compatibility to ODBC engines.

12. Explain ACID rule of thumb for transactions.

Ans : Transaction must be Atomic (it is one unit of work and does not dependent on previous and following transactions), Consistent (data is either committed or roll back, no “in-between” case where something has been updated and something hasn’t), Isolated (no transaction sees the intermediate results of the current transaction), Durable (the values persist if the data had been committed even if the system crashes right after).