1. Difference between an object and a class?
2. Difference between overloading and overriding?
3. Difference between delegate and events?
4. Difference between Interface and Abstract Class?
5. Difference between Class and Structure?
6. Difference between Reference Type and Value Type?
7. Difference between Generics and Non Generics
Collection?
8. Difference between Array and ArrayList?
9. Difference between List and ArrayList?
10. Difference between delegate and events?
11. Difference between string and stringbuilder?
12. Difference between ienumerable and iqueryable?
13. Difference between Private and Static Constructor?
14. Difference between properties and methods?
15. Difference between Singleton Pattern and static class?
16.Difference between IDisposable and Finalize?
17.
Difference
between Constant and Read-only
Difference between
Class and Object
S.No
|
Class
|
Object
|
1
|
It is a datatype that contains the programming logic.
|
It is a chunk of memory that implements the class
logic.
|
2
|
Class is visible in the source code and resides in hard
disk.
|
Object is in the RAM and not visible in source code.
|
3
|
Class is like a template or blueprint of the object. It
implements reusability, encapsulation, inheritance
|
It is the real world implementation of the class. Each
object has its own copy of data.
|
4
|
Example: Button is a class with properties like
Text, BackColor,
events like click, methods like Focus
|
Example: Button1, Button2 are the objects of
Button class.
|
5
|
We can create subclasses
|
We cannot create sub-objects
|
Difference between
Overloading and Overriding
S.No.
|
Overloading
|
Overriding
|
1
|
Having
same method name with different Signatures (parameters).
|
Methods
name and signatures must be same.
|
2
|
Overloading
is the concept of compile time polymorphism.
|
Overriding
is the concept of run time polymorphism.
|
3
|
Two
functions having same name and return type, but with different type and/or
number of arguments is called as Overloading.
|
When a
function of base class is re-defined in the derived class called as
Overriding.
|
4
|
It
doesn't need inheritance.
|
It needs
inheritance.
|
5
|
Method can be different access modifiers.
|
Method should be public.
|
6
|
Overloading = Multiple method signatures, same method
name
|
Overriding = Same method signature (declared virtual),
implemented in sub classes
|
Difference between
Interface and Abstract class
S.No.
|
Interface
|
Abstract
class
|
1
|
Interface support multiple inheritance
|
Abstract class does not support multiple inheritance
|
2
|
Interface doesn’t Contains Data Member
|
Abstract class contains Data Member
|
3
|
Interface doesn’t contains Constructors
|
Abstract class contains Constructors
|
4
|
An interface Contains only incomplete member (signature
of member)
|
An abstract class Contains both incomplete (abstract)
and complete member
|
5
|
An interface cannot have access modifiers by default
everything is assumed as public
|
An abstract class can contain access modifiers for the
subs, functions, properties
|
6
|
Member of interface cannot be Static
|
Only Complete Member of abstract class can be Static
|
Difference between
Structure and Class
S.No.
|
Structure
|
Class
|
1
|
The struct is value type in C# and it inherits from
System.ValueType
|
The class is reference type
in C# and it inherits from the System.Object Type
|
2
|
The struct value will be stored on the stack memory.
|
The class object is stored
on the heap memory. The object will be under garbage collection and
automatically removed when there is no reference to the created objects.
|
3
|
The struct use the array type and its good to use for
read only and light weight object.
|
The class uses the
collection object type and it can perform all the operations and designed for
complex data type storage.
|
4
|
The struct can't be base type to the classes and also
to the other structure.
|
The class can inherit
another class, interface and it can be base class to another class.
|
5
|
The struct can only inherit the interfaces
|
The class can inherit the
interfaces, abstract classes.
|
6
|
The struct can have only constructor.
|
The class can have the
constructor and destructor.
|
7
|
The struct can instantiated without using the new
keyword.
|
The new keyword should be
used to create the object for the class
|
8
|
The struct can't have the default constructor
|
The class will have the
default constructor
|
9
|
The struct is by default sealed class hence it will not
allow to inherit. It can't use the abstract, sealed, base keyword.
|
The class can be declared
as abstract, sealed class
|
10
|
The struct can't use the protected or protected
internal modifier.
|
The class can use all the
access modifiers.
|
11
|
The struct can't initialize at the time of declaration.
|
The class can have the
initializes fields.
|
Difference between Value type and Reference type
S.No.
|
Value type
|
Reference
type
|
1
|
They are
stored on stack
|
They are
stored on heap
|
2
|
Contains
actual value
|
Contains
reference to a value
|
3
|
Cannot contain
null values. However this can be achieved by nullable types
|
Can contain
null values.
|
4
|
Value type is
popped on its own from stack when they go out of scope.
|
Required
garbage collector to free memory.
|
5
|
Memory is
allocated at compile time
|
Memory
is allocated at run time
|
6
|
Ex. -int,
enum, structs.
|
Ex. -class,
interface, delegate, string, object, Array
|
Difference between Generic
and Non
generic collections
S.No.
|
Generic Collections
|
Non generic Collections
|
1
|
These are
the collections that can hold data of same type and we can decide what type
of data that collections can hold.
|
These are
the collections that can hold elements of different data types. It holds all
elements as object type.
|
2
|
Type
Safe, Secure, reduced overhead of type conversions.
|
It
includes overhead of type conversions.
|
3
|
examples of
Generic collections are List , Dictionary etc.
List<double> list = new List<double>();
|
examples of
non-Generic collections are ArrayList and Hash tables
ArrayList arr = new ArrayList();
|
4
|
Similar Generic Type
List<T>
Dictionary<TKey,TValue>
SortedList<TKey,TValue>
Queue<T>
Stack<T>
IEnumerable<T>
N/A (use IEnumerable<T> anything that extends it)
ICollection<T>
IList<T>
Collection<T>
ReadOnlyCollection<T>
N/A (just implement IDictionary<TKey,TValue>
SortedDictionary<TKey,TValue>
KeyedCollection<TKey,TItem>
LinkedList<T>
|
Non-Generic
ArrayList
Hashtable
SortedList
Queue
Stack
IEnumerable
ICollection
N/A
IList
CollectionBase
ReadOnlyCollectionBase
DictionaryBase
N/A
N/A
N/A
|
Difference between Array and ArrayList
collections
S.No.
|
Array
|
ArrayList
|
1
|
They are fixed
length.
|
They are
resizable and variable length.
|
2
|
They are
compiled strong type collection.
|
They are
flexible and can accommodate any data types.
|
3
|
Because arrays
are of fixed size and strong type collection
performance is faster.
|
In arraylist
lots of boxing and unboxing are done there for its
performance is slower.
|
4
|
They are fixed
length.
|
They are
resizable and variable length.
|
5
|
String [ ] str = new String [5]; // here you see that
the length is fixed as [5] and the data type is also defined as string.
|
ArrayList str =
new ArrayList (); // here you see that the length is not fixed and is not
tied up with a data type.
|
Difference between List and ArrayList collections
S.No.
|
Generic Lists (List<T>)
|
ArrayList
|
1
|
Generic List
(List<T>) belongs to the System.Collections.Generic
namespace using
System.Collections.Generic;
|
ArrayList
belongs to the System.Collections namespace
using System.Collections;
|
2
|
In Generic
List (List<T>), T means data type, i.e. string, int, DateTime, etc.
Thus it will store only specific types of objects based on what data type has
been specified while declarations i.e. it is Type Safe. Thus if you have a
Generic List of string you can only store string values, anything else will
give compilation error.
Below I had no
option other than having three different Generic Lists for three different
data types.
List<string> lstString = new List<string>();
lstString.Add("Mudassar Khan");
lstString.Add("Robert Hammond");
lstString.Add("Ramesh Singh");
List<int> lstInt = new List<int>();
lstInt.Add(991);
lstInt.Add(10);
lstInt.Add(4450);
List<DateTime> lstDateTime = new List<DateTime>();
lstDateTime.Add(DateTime.Now);
lstDateTime.Add(DateTime.Now.AddDays(20));
lstDateTime.Add(DateTime.Now.AddHours(-10));
|
ArrayList does
not have type restriction for storing data i.e. it is not Type Safe. You can
store anything in ArrayList. In fact same ArrayList can store multiple types
of objects.
ArrayList arrList = new ArrayList();
arrList.Add(921);
arrList.Add("Mudassar Khan");
arrList.Add(DateTime.Now);
|
3
|
Generic List
stores all data of the data type it is declared thus to getting the data back
is hassle free and no type conversions required.
C#
int number = lstInt[0];
string name = lstString[0];
DateTime dt = lstDateTime[0];
|
ArrayList
stores all data as object thus to get it back you must remember what you
stored where and correspondingly Type Cast it as per its original Type when
stored.
int number = Convert.ToInt32(arrList[0]);
string name = arrList[1].ToString();
DateTime dt = Convert.ToDateTime(arrList[2]);
|
4
|
Generic List
must be used instead of ArrayList unless specific requirement for projects
higher than .Net 2.0 Framework.
|
ArrayList is
mainly for .Net 2.0 Framework projects as during that period Generic List was
not invented.
|
5
|
While running
a Loop on Generic List again it is problem free as we exactly know what the
List contains.
foreach (int number in lstInt)
{
}
foreach (string name in lstString)
{
}
foreach (DateTime dt in lstDateTime)
{
}
|
While running
a Loop on ArrayList you need to use Object data type. Thus this is another
disadvantage as you again do not know what type of data particular item contains.
foreach (object o in arrList)
{
}
|
Difference between
Events and Delegates
S.No
|
Events
|
Delegates
|
1
|
Event can be used in an interface definition
|
Delegate cannot be used in an interface definition
|
2
|
Event can only be invoked from the class that declares
it
|
Delegates can be invoked from child classes and
clients.
|
3
|
Event comes with its pair of accessors i.e Add and
Remove. An event is always assigned and unassigned with a += and -= operator.
|
There is no pair of accessors concept in delegates.
|
4
|
Event has a restrictive signature and must always be of
the form Event (object source, EventArgs args)
|
Delegates do not have restrictive signature as like
events
|
Difference between
String and StrinbBuilder
S.No.
|
String
|
StrinbBuilder
|
1
|
It’s an immutable
|
It’s mutable
|
2
|
Performance wise string is slow because
every time it will create new instance
|
Performance wise stringbuilder is high
because it will use same instance of object to perform any action
|
3
|
In string we don’t have append keyword
|
In StringBuilder we can use append
keyword
|
4
|
String belongs to System namespace
|
Stringbuilder belongs to System.Text
namespace
|
5
|
string strMyValue = "Hello
Visitor";
// create a new string instance instead of changing the old one
strMyValue += "How Are";
strMyValue += "You ??";
|
StringBuilder sbMyValue = new
StringBuilder("");
sbMyValue.Append("Hello Visitor");
sbMyValue.Append("How Are You ??");
string strMyValue = sbMyValue.ToString();
|
Difference between
IEnumerable and IQueryable
S.No.
|
IEnumerable
|
IQueryable
|
1
|
IEnumerable
exists in the System.Collections namespace.
|
IQueryable
exists in the System.Linq Namespace.
|
2
|
IEnumerable is
suitable for querying data from in-memory collections like List, Array and so
on.
|
IQueryable is
suitable for querying data from out-memory (like remote database, service)
collections.
|
3
|
While querying
data from the database, IEnumerable executes "select query" on the
server-side, loads data in-memory on the client-side and then filters the
data.
|
While querying
data from a database, IQueryable executes a "select query" on
server-side with all filters.
|
4
|
IEnumerable is
beneficial for LINQ to Object and LINQ to XML queries.
|
IQueryable is
beneficial for LINQ to SQL queries.
|
5
|
IEnumerable
you get all the records at once
If you use IEnumerable to get the first 5 customers
you end up loading all 1000 and then selecting the first 5.
static void
Main(string[] args)
{
using (var db = new MyDbContext())
{
IEnumerable<Client> clients =
db.Clients.Take(5).ToList();
// ToList() executes the query
straight away
// All the list of clients is loaded
into memory (1000 clients)
// After that, only the first 5 are selected
}
}
|
IQueryable you
only get the records that you want
With IQueryable you only select the first 5 (saving
a lot of resources!)
static void
Main(string[] args)
{
using (var db = new MyDbContext())
{
IQueryable<Client> sameClients
= db.Clients.Take(5).ToList();
// ToList() executes the query
straight away
// The first 5 clients are loaded
into memory
}
}
|
Difference between Dispose & Finalize
Method
S. No.
|
Dispose()
|
Finalize
|
1
|
This dispose method will be used to free unmanaged resources like files, database connection etc.
|
This method also free unmanaged resources like database connections, files etc…
|
2
|
To clear unmanaged resources we need to write code manually to raise dispose() method.
|
It is automatically raised by garbage collection mechanism whenever the object goes out of scope.
|
3
|
This Dispose() method belongs to IDisposable interface.
|
This method belongs to object class.
|
4
|
If we need to implement this method for any custom classes we need to inherit the class from IDisposable interface.
|
We need to implement this method whenever we have unmanaged resources in our code and make sure these resources will be freed when garbage collection process done.
|
5
|
It will not show any effect on performance of website and we can use this method whenever we want to free objects immediately.
//Implement Dispose Method.
public class TestDispose : IDisposable
{
private bool disposed = false;
//Implement IDisposable.
public void Dispose()
{
Dispose(true);
}
protected virtual void Dispose(bool disposing)
{
if (!disposed)
{
if (disposing)
{
// clean unmanged objects
}
// clean unmanaged objects).
disposed = true;
}
}
}
|
It will show effect on performance of website and it will not suitable to free objects immediately.
// Implementing Finalize method
public class Sample
{
//At runtime destructor automatically Converted to Finalize method.
~Sample()
{
// your clean up code
}
}
|
Difference
between Constant and Read-only
S. No.
|
Constant
|
Read-only
|
1
|
Declared and
Initialized in Compile time.
|
The value will be initialized either declaration time or the
constructor of the class allowing you to pass the value at run time.
|
2
|
Const values will evaluate at
compile time only.
|
Read only values will evaluate at
runtime only.
|
3
|
Const value
can’t be changed these will be same at all the time.
|
Value can be changed in the constructor
of the class.
|
4
|
By default Constant is
static, Cannot be declared as static.
|
Can be declared as
Static.
|
5
|
static void Main(string[] args)
{
const
int a = 10;
const
int b = 20;
const
int c = a + b; // no error as both a and b are const variable
int z = 20;
const int d = a + z; // error message "The
expression being assigned to d must be const" on runtime as both a and z
are not Const variable.
Console.WriteLine("Result of a+b = "+c);
Console.ReadKey();
}
|
class Program
{
readonly int x = 10;
public Program()
{
x = 20;// changed the value in the constructor
}
}
|
