.net interview questions and answers - everyone who writes code

Here I am trying to compile some questions from many bloggers and provide answers to what I can. Even though this questions are asked in interview or not, I felt they are important for someone to know to do their job better.

(Source of Questions: Scott Hanselman and other blogs listed in my previous post).

Everyone who writes code

1. What is the difference between an EXE and a DLL?

   An EXE is an executable program by itself. The Operating system can load the instructions from EXE file and run it as a stand alone application. While a DLL is a Dynamic Link Library file that contains binary routines that other executable programs can load while they are run.
   
   P.S. this has nothing to do with .net.
   

2. What is a Windows Service and how does its lifecycle differ from a "standard" EXE?

   Windows Service is type of a cron job in Unix. Windows Service runs in the background and stays in the machine memory until it is unloaded. Windows Service can generate events for itself (e.g. time based events, or file operation based events, network port based events etc.) and then kick off when the event occurs - process the event and then go back to wait for next event. IIS (W3Svc) is such a windows service.
   EXE is generally user invoked program and runs in foreground.
   
   P.S. This has nothing to do with .Net.
   



3. What is the GAC? What problem does it solve?

   Global Assembly Cache. When a .Net program (or class files) run they use many functions available in other DLLs. GAC stores all these common (system) DLLs so that they don't have to be loaded everytime a program runs. One can add or remove DLLs in the GAC.
   

4. Describe the difference between a Thread and a Process?

   Process is a module or a program that operating system allocates memory and cpu for its execution. Process has its own space. Now, a process may want to do parallel processing within itself to perform a specific task. E.g. check spelling while user is typing. Different parallel execution units within a process are called threads. A process contain one or more threads. And each thread belongs to one process. In Windows Task manager one can see all the processes that are currently running.
   
   P.S. This has nothing to do with .Net.

5. What is a PID? How is it useful when troubleshooting a system?



PID is Process Id. It helps in debugging. Generally each system should log the errors with the PID so looking at log file one can find out what events caused a particular error. Many of the tracing tools display PID.

P.S. This has nothing to do with .Net.





6. What is strong-typing versus weak-typing? Which is preferred? Why?




Strong Typing means each of the object in the program has its type and type-casting is not used to cast object of one type to another. This way compiler will generate errors if an object of one type is being assinged to object of another type. This reduces run time errors.

Weak typing is where objects are dynamically created of a specific type and then assigned to objects of their base class types. Objects may change their type at the Run time. Compiler does not catch if there are any errors in assignments or comparison or any such operations on weakly typed objects.

What is preferable - depends entirely on the need. Though its common to avoid weak-typing unless you know what you are doing.

P.S. Again, this is not too much related to .net as such. This is common programming concept.




7. What is the maximum amount of memory any single process on Windows can address? Is this different than the maximum virtual memory for the system? How would this affect a system design?

Rather than reproducing this answer here is a link: Dotnet Doc Link
In short, maximum 4 GB memory but 2 GB for OS and 2 GB for process.


8. Corillian's product is a "Component Container." Name at least 3 component containers that ship now with the Windows Server Family.


I did not knew about this one earlier. So, here is a link to someone's answer:
Dotnet Doc Link

What that says in nutshell is- Component is the class that implements IComponent. Container is a class that implments IContainer and Container will contain the components.


9. How many processes can listen on a single TCP/IP port?

As far as I know, ONE.




10. Can DateTimes be null?
    

    No. You can use DateTime.MinValue if needed.

11. Is string a value type or a reference type?

reference type.

12. What is the difference between a Debug and Release build? Is there a significant speed difference? Why or why not?

Debug build will contain all the debug information that helps in debugging a program e.g. PDB files. Release mode does not contain any extra information. Some solutions may use compiler directives to execute different codes in DEBUG mode and in RELEASE mode.

There could be speed difference depending upon the size of the project. Its never a good idea to use DEBUG version in production environment.