Mostly Asked C# Interview Questions

 1.Does C# support multiple-inheritance? 

    No. But you can use Interfaces.

2.Where is a protected class-level variable available? 

    It is available to any sub-class derived from a base class

3.Are private class-level variables inherited? 

    Yes, but they are not accessible. 

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. 

6.Which class is at the top of .NET class hierarchy? 

    System.Object. 

7.What does the term immutable mean?

    The data value may not be changed. 

8.What’s the difference between System.String and System.Text.StringBuilder classes?

    System.String is immutable.

    System.StringBuilder was designed to have a mutable string where a variety of operations     can be performed. 

9.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.

10.Can you store multiple data types in the System? Array?

    No

11.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 identical object.

12.How can you sort the elements of the array in descending order?

      By calling Sort() and then Reverse() methods. 

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

14.What class is underneath the SortedList class?

    A sorted HashTable. 

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

16.What’s the C# syntax to catch any possible exception?
    A catch block that catches the exception of type System. Exception.

17.Can multiple catches blocks are executed for a single try statement?
    No. Once the proper catch block processed, control is transferred to the finally block.

18.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).