C# Interview Questions


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General Questions

1.Does C# support multiple-inheritance?
Ans. No! It may be achieved however, using interfaces.
 
2.Who is a protected class-level variable available to?
Ans.It is available to any sub-class (a class inheriting
this class).
 
3.Are private class-level variables inherited?
Ans. 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”.
Ans. 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?
Ans.System.Object.
 
6.What does the term immutable mean?
Ans.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?
Ans.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?
Ans.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?
Ans.No.
 
10.What’s the difference between the
System.Array.CopyTo() and System.Array.Clone()?
Ans.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?
Ans.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?
Ans.HashTable.
 
13.What class is underneath the SortedList class?
Ans.A sorted HashTable.
 
14.Will the finally block get executed if an
exception has not occurred?¬
Ans.Yes.
 
15.What’s the C# syntax to catch 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 {}.
 
16.Can multiple catch blocks be executed for a
single try statement?
Ans.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.
Ans.Presentation (UI), Business (logic and underlying
code) and Data (from storage or other sources).

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