C# questions whit solutions

C#  questions whit solutions

This is a list of questions I have gathered from other sources and created myself over a period of time from my experience, many of which I felt where incomplete or simply wrong.  I have finally taken the time to go through each question and correct them to the best of my ability.  However, please feel free to post feedback to challenge, improve, or suggest new questions.  I want to thank those of you that have contributed quality questions and corrections thus far.

There are some question in this list that I do not consider to be good questions for an interview.  However, they do exist on other lists available on the Internet so I felt compelled to keep them easy access.

General Questions

1.    Does C# support multiple-inheritance?

No.
 

2.    Who is a protected class-level variable available to?
It is available to any sub-class (a class inheriting this class).
 

3.    Are private class-level variables inherited?
Yes, but they are not accessible.  Although they are not visible or accessible via the class interface, they are inherited.
 

4.    Describe the accessibility modifier “protected internal”.
It is available to classes that are within the same assembly and derived from the specified base class.
 

5.    What’s the top .NET class that everything is derived from?
System.Object.
 

6.    What does the term immutable mean?
The data value may not be changed.  Note: The variable value may be changed, but the original immutable data value was discarded and a new data value was created in memory.
 

7.    What’s the difference between System.String and System.Text.StringBuilder classes?
System.String is immutable.  System.StringBuilder was designed with the purpose of having a mutable string where a variety of operations can be performed.
 

8.    What’s the advantage of using System.Text.StringBuilder over System.String?
StringBuilder is more efficient in cases where there is a large amount of string manipulation.  Strings are immutable, so each time a string is changed, a new instance in memory is created.
 

9.    Can you store multiple data types in System.Array?
No.
 

10. What’s the difference between the System.Array.CopyTo() and System.Array.Clone()?
The Clone() method returns a new array (a shallow copy) object containing all the elements in the original array.  The CopyTo() method copies the elements into another existing array.  Both perform a shallow copy.  A shallow copy means the contents (each array element) contains references to the same object as the elements in the original array.  A deep copy (which neither of these methods performs) would create a new instance of each element's object, resulting in a different, yet identacle object.
 

11. How can you sort the elements of the array in descending order?
By calling Sort() and then Reverse() methods.
 

12. What’s the .NET collection class that allows an element to be accessed using a unique key?
HashTable.
 

13. What class is underneath the SortedList class?
A sorted HashTable.
 

14. Will the finally block get executed if an exception has not occurred?­
Yes.
 

15. What’s the C# syntax to catch any possible exception?
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 {}.
 

16. Can multiple catch blocks be executed for a single try statement?
No.  Once the proper catch block processed, control is transferred to the finally block (if there are any).
 

17. Explain the three services model commonly know as a three-tier application.
Presentation (UI), Business (logic and underlying code) and Data (from storage or other sources).
   

C#  questions whit solutions