(A) Where are all .NET Collection classes located ?
System.Collection namespace has all the collection classes available in .NET.
(A) What is ArrayList ?
Array whose size can increase and decrease dynamically.Arraylist can hold item of different
types.As Arraylist can increase and decrease size dynamically you do not have to use the
REDIM keyword.You can access any item in array using the INDEX value of the array
position.
(A) What’s a HashTable ? Twist :- What’s difference between HashTable and ArrayList ?
You can access array using INDEX value of array , but how many times you know the
real value of index.Hashtable provides way of accessing the index using a user identified
KEY value , thus removing the INDEX problem.
(A) What are queues and stacks ?
Queue is for first-in, first-out (FIFO) structures. Stack is for last-in, first-out (LIFO)
structures.
(B) What is ENUM ?
It’s used to define constants.
(B)What’s Operator Overloading in .NET? It provides a way to define and use operators such as +, -, and / for user-defined classes
or structs. It allows us to define/redefine the way operators work with our classes and
structs. This allows programmers to make their custom types look and feel like simple
types such as int and string.
VB.NET till now does not support operator overloading. Operator overloading is done
by using the “Operator” keyword.
(B)What’s the significance of Finalize method in .NET?
.NET Garbage collector does almost all clean up activity for your objects. But unmanaged
resources (ex: - Windows API created objects, File, Database connection objects, COM
objects etc) is outside the scope of .NET framework we have to explicitly clean our
resources. For these types of objects .NET framework provides Object.Finalize method
which can be overridden and clean up code for unmanaged resources can be put in this
section.
(A)Why is it preferred to not use finalize for clean up?
Problem with finalize is that garbage collection has to make two rounds in order to remove
objects which have finalize methods.
In this scenario there are three objects Object1, Object2 and Object3. Object2 has the
finalize method overridden and remaining objects do not have the finalize method
overridden.
Now when garbage collector runs for the first time it searches for objects whose memory
has to freed. He sees three objects but only cleans the memory for Object1 and Object3.
Object2 it pushes to the finalization queue.
Now garbage collector runs for the second time. He see’s there are no objects to be freed
and then checks for the finalization queue and at this moment it clears object2 from the
memory.
So if you notice that object2 was freed from memory in the second round and not first.
That’s why the best practice is not to write clean up Non.NET resources in Finalize
method rather use the DISPOSE.
(I)How can we suppress a finalize method?
GC.SuppressFinalize ()
(B)What’s the use of DISPOSE method?
Dispose method belongs to IDisposable interface. We had seen in the previous section
how bad it can be to override the finalize method for writing the cleaning of unmanaged
resources. So if any object wants to release its unmanaged code best is to implement
IDisposable and override the Dispose method of IDisposable interface. Now once your
class has exposed the Dispose method it’s the responsibility of the client to call the
Dispose method to do the cleanup.
(A)How do I force the Dispose method to be called automatically, as clients can forget to call Dispose method?
Call the Dispose method in Finalize method and in Dispose method suppress the finalize
method using GC.SuppressFinalize. Below is the sample code of the pattern. This is the
best way we do clean our unallocated resources and yes not to forget we do not get the hit
of running the Garbage collector twice.
Note:- It will suppress the finalize method thus avoiding the two trip.
Public Class ClsTesting
Implements IDisposable
Public Overloads Sub Dispose()Implements IDisposable.Dispose
' write ytour clean up code here
GC.SuppressFinalize(Me)
End Sub
Protected Overrides Sub Finalize()
Dispose()
End Sub
End Class
(I)In what instances you will declare a constructor to be
private?
When we create a private constructor, we can not create object of the class directly from
a client. So you will use private constructors when you do not want instances of the class
to be created by any external client. Example UTILITY functions in project will have no
instance and be used with out creating instance, as creating instances of the class would
be waste of memory.
(I)Can we have different access modifiers on get/set
methods of a property ?
No we can not have different modifiers same property. The access modifier on a property
applies to both its get and set accessors. (I)If we write a goto or a return statement in try and catch
block will the finally block execute ?
The code in the finally always runs even if there are statements like goto or a return
statements.
(A)What is Indexer ?
An indexer is a member that enables an object to be indexed in the same way as an array.
(A)Can we have static indexer in C# ?
No.
(A)In a program there are multiple catch blocks so can it
happen that two catch blocks are executed ?
No once the proper catch section is executed the control goes to finally block.So there
will not be any scenarios in which multiple catch blocks will be executed.
(A) What is the difference between System.String and
System.StringBuilder classes?
System.String is immutable; System.StringBuilder can have mutable string where a variety
of operations can be performed.
