C# Interview Questions And Answers: part-2


Ques 1. 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.


Ques 2. What’s a delegate?
Ans : A delegate object encapsulates a reference to a method. In C++ they were referred to as function pointers.


Ques 3. What’s a multicast delegate?
Ans : It’s a delegate that points to and eventually fires off several methods.


Ques 4. 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.


Ques 5. What are the ways to deploy an assembly?
Ans : An MSI installer, a CAB archive, and XCOPY command.


Ques 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.


Ques 7. What namespaces are necessary to create a localized application?
Ans : System.Globalization, System.Resources.


Ques 8. What’s the difference between // comments, /* */ comments and /// comments?
Ans : Single-line, multi-line and XML documentation comments.


Ques 9. How do you generate documentation from the C# file commented properly with a command-line compiler?
Ans : Compile it with a /doc switch.


Ques 10. What’s the difference between and XML documentation tag?
Ans : Single line code example and multiple-line code example.


Ques 11. Is XML case-sensitive?
Ans : Yes, so and are different elements.


Ques 12. 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.


Ques 13. What does the This window show in the debugger?
Ans : It points to the object that’s pointed to by this reference. Object’s instance data is shown.


Ques 14. 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.


Ques 15. What’s the difference between the Debug class and Trace class?
Ans : Documentation looks the same. Use Debug class for debug builds, use Trace class for both debug and release builds.


Ques 16. 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.


Ques 17. Where is the output of TextWriterTraceListener redirected?
Ans : To the Console or a text file depending on the parameter passed to the constructor.


Ques 18. How do you debug an ASP.NET Web application?
Ans : Attach the aspnet_wp.exe process to the DbgClr debugger.


Ques 19. 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).


Ques 20. Can you change the value of a variable while debugging a C# application?
Ans : Yes, if you are debugging via Visual Studio.NET, just go to Immediate window.


Ques 21. Explain the three services model (three-tier application)?.
Ans : Presentation (UI), business (logic and underlying code) and data (from storage or other sources).


Ques 22. 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.


Ques 23. What’s the role of the DataReader class in ADO.NET connections?
Ans : It returns a read-only dataset from the data source when the command is executed.


Ques 24. What is the wildcard character in SQL?
Ans : Let’s say you want to query database with LIKE for all employees whose name starts with La. The wildcard character is %, the proper query with LIKE would involve ‘La%’.


Ques 25. 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).


Ques 26. What connections does Microsoft SQL Server support?
Ans : Windows Authentication (via Active Directory) and SQL Server authentication (via Microsoft SQL Server username and passwords).


Ques 27. Which one is trusted and which one is untrusted?
Ans : 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.


Ques 28. Why would you use untrusted verificaion?
Ans : Web Services might use it, as well as non-Windows applications.


Ques 29. What does the parameter Initial Catalog define inside Connection String?
Ans : The database name to connect to.


Ques 30. What’s the data provider name to connect to Access database?
Ans : Microsoft.Access.


Ques 31. What does Dispose method do with the connection object?
Ans : Deletes it from the memory.


Ques 32. What is a pre-requisite for connection pooling?
Ans : Multiple processes must agree that they will share the same connection, where every parameter is the same, including the security settings.