Embed Size (px)
DESCRIPTION
c##
Citation preview
www.csetu
be.in
1
1
CS2041 / CS706 - C# and .NET Framework (Elective III)
VII-Sem-IT 2008-Regulations
TWO MARK Question & Answers
-------------------------------------------------------------------------------------------- UNIT-I
1) Define a) Problem Domain b) Solution Domain
Solving a problem involves conversion of problem domain or problem space to Solution domain.
The problem domain is a sector or sectors to which the problem belongs. It is an area of interest having clearly
defined boundaries. It forms an autonomous body describing high level features.
The Solution domain is the subject matter that is of concern to the computer system and the
implementor of the system. It describes the features in a manner which can be understood by the computer.
The problem domain refers to the scope of the problem being addressed by the software system. While
solving a problem using a computer ,its solution is in the form of a program.
2) Define in brief Object Oriented Principles.
OOP is based on three key principles: encapsulation, inheritance, and polymorphism.
1. Encapsulation binds together code and data.
2. Inheritance is the mechanism by which one class can inherit the functionality of another.
3. Polymorphism lets you define one interface that describes a general set of actions.
These attributes work together in a powerful way that enables the construction of reliable, reusable, and
extensible programs.
3) Define a)Abstraction b)Encapsulation
a) The essential features of an entity is known as abstraction. A feature may be either an attribute
reflecting a property(or state or data) or an operation reflecting a method( or a behavior or function).
Abstraction defines necessary and sufficient description rather than implementation.
An inteterface is an abstraction and is the separation of an interface and its implementation is an
example of abstraction.
b) From the user’s point of view ,a number of features are packaged in a capsule to form an entity.
This entity offers a number of services in the form of interfaces by hiding the implementation detail.
The adcantages of encapsulation are a) Information hiding b) Implementation independence
4) Differentiate an interface from its implementation.
Slno Interface Implementation
1 It is user’s view point. (What
part)
It is supplier’s view point.
(How part)
2 It is used to interact with the
outside world
It describes how the delegated
responsibility is carried out.
3 User is permitted to access the
interfaces only
Functions or methods are
permitted to access the data.
4 It
encapsulates the knowledge
about the object.
It provides the restriction of
access data by the user.
www.csetube.in
www.csetu
be.in
2
2
5) Define a) Class b) Object
A group of objects sharing common structure and behavior is called a class. A class is
a template for creating objects.
An object is an instance of a class. An object has identity,state and behavior.
A C# program is basically a collection of classes. A class is defined by a set of declaration statements
and methods containing instructions known as executable statements.
6) Differentiate an Object and a Class.
A class is a template for creating an object. An object is an instance of a class. An object
has memory and reference.
The class is C#'s basic unit of program functionality. However, it is more than that. It is also C#'s
foundation for object-oriented programming (OOP)
7) What are the advantages of OOP?
Code reuse
Seamless transition from different phases of s/w development
Modularity
8) What are the applications of C# ?
1) console applications
2) Winows applications
3) Developing windows controls
4) Developing ASP.NET projects
5) Creating Web Controls
6) Providing web services
7) Developiong .NET component library
9) What is .NET Framework?
o .NET represents an advanced new generation of software that will drive the Next
Generation Internet. Its purpose is to make information available any time, any place,
and on any device.
o Quick Definition
.NET is an initiative to integrate all Microsoft products with the “Next
Generation” web.
o .NET is a software framework that includes everything requiered for developing
software for web services. It integrates presentation technologies,component
technologies,and data technologies on a single platform so as to enable users to develop
internet applications as easily as thyey do on desktop systems.
o In brief .NET platform provides a new environment for creating and running
robust,scalable and distributed applications over the web.
o It consists of three distinct technologies
a)Common Language Runtime
o Framework base classes
o User and program Interfaces(ASP.NET and Winforms)
www.csetube.in
www.csetu
be.in
3
3
10) State the Charateristics of C#.
a) Simple – C# simplifies C++ by eliminating irksome operations such as →,:: and pointers
b) Consistent – C# supports unified type system
c) Modern – Automatic garbage Collection
Modern approach to debugging
Rich intrinsic model for error handling
Decimal data type for financial applications
Robust security model
d) Object Oriented
Supports encapsulation,Inheritance, and Polymorphism
In C#,every thing is an object. There is no global functions,variables and constants
e) Type Safe – promotes robust programs
Following are some type safe measures :
i. All dynamically allocated objects and arrays are initialized to zero
ii. Use of uninitialized variables produces an error message by the compiler
iii. Access to arrays are range checked and warned if it goes out-of bounds
iv. C# does not permit unsafe casts
v. C# enforces overflow checking in arithmetic operations
vi. Reference paramets that are passed are type-safe
vii. C# supports automatic garbage collection
f) C# is versionable – Making new versions of software modules work with existing applications
is known as versioning. C# provides support for versioning with the help of new and override
keywords. Using versioning,a programmer can guarantee that his new class library will maintain
binary compatibility with the existing client applications.
g) Compatible - C# enforces the .NET common Language specifications and therefore allows
inter-operation with other .NET languages. C# provides support for transparent acces to COM
and OLE automation
h) Interoperability – C# provides support for using COM objects
11) Write the compilation and execution commands of a C# source program.
Overview of a C# Program
Hello, world
The canonical “Hello, world” program can be written in C# as follows:
www.csetube.in
www.csetu
be.in
4
4
using System;
class Hello
{
static void Main()
{
Console.WriteLine(“Hello, world”);
}
}
Compiling and Running the Application
The default file extension for C# programs is .cs, as in hello.cs. Such a program can be
compiled with the command line directive
csc hello.cs
Which produces an executable program named hello.exe. The output of the program is:
Hello, world
12) What are tokens? What are the tokens supported in C# Language?
The smallest, non execuatable ,textual elements in a program are refered to as tokens. The compiler
recognizes them by building up expressions and statements.
In simple sterms,a C# program is a collection of tokens. C# includes the following five types of
tokens :
Keywords
Identifiers
Literals
Operators
Punctuators
Keywords are essential part of language definition. They implement specific features of the
language. They are reserved,and cannot be used as identifiers except when they are prefacedby
the @ character.
Few C# keywords are :
bool float namespace static
byte for new string
char foreach private this
catch finally override throw
13) What are Identifiers?
Identifiers are programmer-designed tokens. They are used for naming
classes,methods,variables,labels,namespaces,interfaces etc.
The rules for defining identifiers are :
www.csetube.in
www.csetu
be.in
5
5
a) They have alphabets,digits and underscore characters.
b) They must not begin with a digit.
14) What are Escape Sequences? Enumerate differenct Esc Sequences.
Escape sequences are special backslash character constants that are used in output methods. For
example '\n' stands for a newline character.
The following tables lists the common Escape Sequences used in C#.
Literal
constant
Meaning
'\a' alert
'\b' Back space
'\f' Form feed
'\n' New line
'\r' Carriage return
'\t' Horizontal tab
'\v' Vertical tab
'\'' Single quote
'\''' Double quote
'\\' Back slash
'\o' null
15) Explain the difference between a Value type and reference type. Illustrate with some
examples
Value types:
* Value types can be created at compile time.
* Stored in stack memory.
* Garbage collector can't access the stack
* value types holds the data directly
* No default values will be stored in value types
* Examples for value types: Predefined datatypes,structures,enums
Reference types:
* Reference types can be created at run time.
* Stored in heap memory
* Garbage collector can access heap
* Reference types holds the data indiredtly
* Reference types holds default value
* Examples for reference types: Classes,objects,Arrays,Indexers,Interfaces
www.csetube.in
www.csetu
be.in
6
6
16) Explain with example declaration of primitive data types in C#.
What is Data Type?
The type of data that a variable contains is called Data Type (type). A Data Type is a
classification of things that share similar type of qualities or characteristics or behavior.
C# is strongly typed language so every variable and object must have a type.
There are two types of data type in C#
1. primitive types (or) predefined
Ex: byte, short, int, float, double, long ,char, bool, DateTime, string, object etc..
2. non-primitive types (or) User Defined
Ex: class , struct , enum , interface, delegate, array.
In C#, based on what a variable contains there is two types of built-in data type
Value types
A variable holds actual values then that type of data types are value types. These value types are
stored in “stack” memory and these value types are fixed in size. If you assign a value of a
variable to another variable it will create two copies.
Ex: byte, short, int, float, double, long ,char, bool, DateTime.
Primitive data types are value types except string, object.
Object type is superior to all types. It can store any type or any size of data. It helps in
inheritance process.
Struct, enum are value types.
Reference types
A variable holds a reference to the value, then that type of data types are reference types. These
reference types are stored in “heap” memory and these types are not fixed in size. They are
maintained in system managed heap but it also uses stack to store reference of the heap. Two
primitive types (string and object) and non-primitive data types (class, interface & delegate) are
examples of reference type.
Ex: class, interface, delegate, string, object and array
17) Define a “Class” in C#.
A class is a user-defined data type with a template that serves to define it properties. Once a
class type has been defined, we can create variables of that type using declarations wich are
similar to basic type declarations. These variables are known as instances of classes, which are
actual objects.
www.csetube.in
www.csetu
be.in
7
7
The syntax for class definition is :
Class className
{
[ variables declaration;]
[ methods declaration;]
}
18) Differntiate Passing by reference and Passing by value.
Passing by Reference vs. Passing by Value
By default, when a value type is passed to a method, a copy is passed instead of the object itself.
Therefore, changes to the argument have no effect on the original copy in the calling method.
You can pass a value-type by reference by using the ref keyword.
When an object of a reference type is passed to a method, a reference to the object is passed.
That is, the method receives not the object itself but an argument that indicates the location of the
object. If you change a member of the object by using this reference, the change is reflected in
the argument in the calling method, even if you pass the object by value.
19) Differentiate value and reference parameters with an example.
Passing Parameters
In C#, arguments can be passed to parameters either by value or by reference. Passing by reference
enables function members, methods, properties, indexers, operators, and constructors to change the
value of the parameters and have that change persist in the calling environment. To pass a parameter by
reference, use the ref or out keyword. For simplicity, only the ref keyword is used in the examples in this
topic.
The following example illustrates the difference between value and reference parameters.
class Program
{
static void Main(string[] args)
{
int arg;
// Passing by value.
// The value of arg in Main is not changed.
arg = 4;
squareVal(arg);
Console.WriteLine(arg);
// Output: 4
// Passing by reference.
// The value of arg in Main is changed.
arg = 4;
www.csetube.in
www.csetu
be.in
8
8
squareRef(ref arg);
Console.WriteLine(arg);
// Output: 16
}
static void squareVal(int valParameter)
{
valParameter *= valParameter;
}
// Passing by reference
static void squareRef(ref int refParameter)
{
refParameter *= refParameter;
}
}
20) What is a signature of a method?
Method Signatures
Methods are declared in a class or struct by specifying the access level such as public or private, optional
modifiers such as abstract or sealed, the return value, the name of the method, and any method parameters.
These parts together are the signature of the method.
21) Explain with examples the purpose of Constructor/Destructor
Constructors are special methods, used when instantiating a class. A constructor can never return
anything, which is why you don't have to define a return type for it. A normal method is defined
like this:
For example, we have a Car class, with a constructor which takes a string as argument. Of
course, a constructor can be overloaded as well, meaning we can have several constructors, with
the same name, but different parameters. Here is an example:
public Car()
{
}
public Car(string color)
{
this.color = color;
}
If you run this code, you will see that the constructor with no parameters is called first. This can be
used for instantiating various objects for the class in the default constructor, which can be called
from other constructors from the class. If the constructor you wish to call takes parameters, you
can do that as well.
Here is a simple example:
www.csetube.in
www.csetu
be.in
9
9
public Car(string color) : this()
{
this.color = color;
Console.WriteLine("Constructor with color parameter called!");
}
public Car(string param1, string param2) : this(param1)
{
}
If you call the constructor which takes 2 parameters, the first parameter will be used to
invoke the constructor that takes 1 parameter.
Destructors
Since C# is garbage collected, meaning that the framework will free the objects that you no
longer use, there may be times where you need to do some manual cleanup. A destructor, a
method called once an object is disposed, can be used to cleanup resources used by the
object. Destructors doesn't look very much like other methods in C#. Here is an example of
a destructor for our Car class:
~Car()
{
Console.WriteLine("Out..");
}
Once the object is collected by the garbage collector, this method is called.
22) How will you create objects of a class?
Creating an object is referred to as instantiating an object. Objects in C# are created ujsing the new
operator.
EXAMPLE
Class Rectangle
{
Int length;
Int width;
Public void GetData(int x, int y)
{
Length = x;
Width = y;
}
}
Object creation steps :
(1) Declare class Rectangle as shown above.
(2) Create an object of type Rectangle :
Rectangle rect1; // declare the variable to hold reference
www.csetube.in
www.csetu
be.in
10
10
(3) Rect1 = new Rectangle(); // instantiate ( Assigns the object reference to the variable)
Steps (2) and (3) can be combined into one as shown below :
Rectangle rect1 = new Rectangle();
Action
Statement Result
Declare
variable
rect1 of
type
Rectangle
Rectangle rect1;
rect1
Rect1 is the variable to hold
the object reference
Instantiate Rect1 = new
Rectangle( );
rect1 Rectangle object
Rect1 points to object
instance
23) How will you access the members of a created object?
Rectangle rect1;
= new Rectangle( );
Rectangle rect2 = new rectangle( );
The instance variables of the Rectangle class may be
accessed and assigned values as follows :
rect1.length = 15; rect1.width = 10;
rect2.length = 20; rect2.width = 12;
We can also call the GetData method to set values for variable length and width as follows ;
Rect1.GetData(15,10); // calling the method
24) What are constructos? Give an example.
It should be noted that the objects that are created must be initialized. One approach would
be to use dot operator to access instance variables and assign values. It is a tedious approach to
initialize instance variable.
It would be simpler and more concise to initialize an object when it is first created.
C# supports a special type of method, called a constructor, that enables an object to initialize itself
when it is created.
Example
Class Rectangle
{
Public int length;
Public int width;
Public Rectangle(int x,int y) // constructor method
{
Length = x;
Width = y;
}
}
Null
www.csetube.in
www.csetu
be.in
11
11
Class test
{
Public static void Main()
{
Rectangle rect1 = new Rectangle(15,10); // calling constructor
….
}
25) Explain the usage of „this‟ reference.
this
The this keyword refers to the current instance of the class. Static member functions do not have
a this pointer. The this keyword can be used to access members from within constructors, instance
methods, and instance accessors.
The following are common uses of this:
To qualify members hidden by similar names:
example:
public Employee(string name, string alias)
{
this.name = name;
this.alias = alias;
}
26) What are access modifiers? Explain their purpose.
Access Modifiers
Access modifiers are keywords used to specify the declared accessibility of a member or a type.
public
protected
internal
private
public
The public keyword is an access modifier for types and type members. Public access is the most
permissive access level. There are no restrictions on accessing public members.
www.csetube.in
www.csetu
be.in
12
12
private
The private keyword is a member access modifier. Private access is the least permissive access
level. Private members are accessible only within the body of the class or the struct in which they
are declared.
protected
The protected keyword is a member access modifier. A protected member is accessible from
within the class in which it is declared, and from within any class derived from the class that
declared this member.
A protected member of a base class is accessible in a derived class only if the access takes place
through the derived class type. For example, consider the following code segment:
internal
The internal keyword is an access modifier for types and type members. Internal members are
accessible only within files in the same assembly.
A common use of internal access is in component-based development because it enables a group
of components to cooperate in a private manner without being exposed to the rest of the
application code. For example, a framework for building graphical user interfaces could provide
Control and Form classes that cooperate using members with internal access. Since these
members are internal, they are not exposed to code that is using the framework.
27) Differentiate static and non-static members of a class.
C# Static Method
Static methods have no instances. They are called with the type name, not an instance identifier.
They are slightly faster than instance methods because of this. Static methods can be public or
private. They cannot use the this instance expression.
Static Modifier
Key point:Static methods are called without an instance reference.
Example
This program defines both static methods and regular instance methods and calls them both. The
static methods use the static keyword somewhere in the method declaration signature, usually as
the first keyword or the second keyword after public.
Static methods cannot access non-static class level members and do not have a 'this' pointer.
Instance methods can access those members, but must be called through an object instantiation,
which causes another step and level of indirection.
www.csetube.in
www.csetu
be.in
13
13
28) What is enumeration?
Enumeration is a user-defined integer type which provide a way for attaching names to numbers.
29) Explain the syntax for declaring data type enumeration and give examples.
An enumeration (enum) is a value data type. It is a special integer data type. The declaration of this
data type defines a type name for a related group of symbolic constants. The associating integral data
type is known as underlying data type.
The syntax for defining enum is
Enum enumBase[:dataType]
{
Enumerator1,
Enumerator2,
….
enumeratorN
}
Where
Enum is a keyword indicating enumerator data type.
Enum Base is the name used to identify the specific enumeration.
Data type is one of the types from byte,sbyte,short,ushort,int,uint,long, or ulong.
Enumerator1,enumerator2,…enumeratorN are list of identifiers representing enum members.
EXAMPLE
enum Vehicle : byte
{
Car,bus,van,lorry
}
is an enumeration with underlying byte data type, and
enum Vehicle
{
Car,bus,van,lorry
}
is an enumeration with underlying int data type.
30) What is type conversion? Explain with examples.
A data type can be explicitly converted into a desired data type. This feature is known
as casting. It is accomplished by using the cast operator.
www.csetube.in
www.csetu
be.in
14
14
The general format for type conversion :
(data type) expression
Example
(long) (10+25) converts the integer constant 35 to long.
(float) 1 converts the integer constant 1 to the float value 1.0
31) Differentiate class and structure
Category Structure (struct) class
Data Type Value type Reference type
Storage type Stack Heap
Inheritance Not supported Supported
Default values zero Null
Field iniialization Not permitted permitted
Construcor Not allowed Allowed
Destructors Not supported Supported
Assignment
operation
Copies the values Copies the reference
32) What is type conversion? Explain with examples.
A data type can be explicitly converted into a desired data type. This feature is known
as casting. It is accomplished by using the cast operator.
The general format for type conversion :
(data type) expression
Example
(long) (10+25) converts the integer constant 35 to long.
(float) 1 converts the integer constant 1 to the float value 1.0
33) Explain boxing and unboxing. Boxing
Conversion of value type to an object type is known as boxing. Boxing permits an implicit conversion of
value type to an object type. Boxing a value means allocating an object instance , and the value of the
value type is copied into that object instance.
Example
The following is the value type declaration :
Int x = 256;
The following statement implicitly applies the boxing operation on the variable x :
Object obj = x;
The value of variable x is stored on stack and it can be directly accessed. The boxing of x results in
allocating memory on stack for obj reference and memory for data on heap.
www.csetube.in
www.csetu
be.in
15
15
Unboxing
Unboxing performs the opposite operationnof boxing. Conversion of object type to value type is known
as Unboxing.
Example
Object obj = 256;
Int x = (int)obj; // unboxing
34) Explain checked and unchecked operators.
Overflow checking for arithmetic operations and conversion of integer types are
controlled by checked and unchecked operators.
If an operation is checked, an overflow error will be thrown when an overflow occurs.
If it is not checked , the error is not reported and the overflowing bits are discarded.
Example
Int p = checked ( x * y ); // will check for the overflow if any, and an error is
reported(or an exception is thrown).
The code
Int p = unchecked ( x * y) ; // will result in loss of bits when an overflow occurs.
35) Explain with syntax and flowchart a) While loop construct b) Do while loop construct
c)for loop construct
While loop construct
While (boolExpr)
{
embedStmt;
}
Do While loop construct
Do
[
embedStmt;
}
While (boolExpr);
for loop construct
for (Expr_1; boolExpr; expr_2)
{
embedStmt;
}
36) What are exceptions and How exceptions are handled in C# programs?
During execution of a program, an unexpected situation or errors may occur and
they are called exceptions. When an exception occurs , the linear flow of control through the
program is altered. When an exception is thrown, the CLR searches for a method that
can handle the exception. An exception handler is used to catch the exception that is thrown. Exception handling is an in built mechanism in .NET framework to detect and handle run time
errors. Exceptions are defined as anomalies that occur during the execution of a program. The
.NET framework provides a rich set of standard exceptions that are used during exceptions
handling.
37) Give examples of predefined Exception classes in C#.
Sno Exception Type remarks
1 ArgumentException Invalid argument
2 ArithmeticException Arithmetic Overflow or Underflow
3 IndexOutOfRangeException An array index is out of range
4 StackOverflowException Stack overflow error
5 DivideByZeroException Error by dividing a value by zero
6 ArgumentNullException A null argument is passed to a method
resulting in an error
www.csetube.in
www.csetu
be.in
16
16
38) Explain briefly the exception handling mechanism in C#.
Exception handling is an in built mechanism in .NET framework to detect and handle run time
errors. The .NET framework contains lots of standard exceptions. The exceptions are anomalies that
occur during the execution of a program. They can be because of user, logic or system errors.
C# provides three keywords try, catch and finally to do exception handling. The try encloses the
statements that might throw an exception whereas catch handles an exception if one exists. The finally
can be used for doing any clean up process.
The general form try-catch-finally in C# is shown below
try
{
// Statement which can cause an exception.
}
catch(Type x)
{
// Statements for handling the exception
}
finally
{
//Any cleanup code
}
If any exception occurs inside the try block, the control transfers to the appropriate catch block and
later to the finally block.
39) Explain the syntax of a) the throw statement b) the try statement c) user defined exceptions
// try_catch_example.cs
using System;
class MainClass
{
static void ProcessString(string s)
{
if (s == null)
{
throw new ArgumentNullException();
}
}
static void Main()
{
try
{
string s = null;
ProcessString(s);
}
catch (Exception e)
{
www.csetube.in
www.csetu
be.in
17
17
Console.WriteLine("{0} Exception caught.", e);
}
}
}
---------------------------------------------------------- // try_catch_finally.cs
using System;
public class EHClass
{
static void Main()
{
try
{
Console.WriteLine("Executing the try statement.");
throw new NullReferenceException();
}
catch (NullReferenceException e)
{
Console.WriteLine("{0} Caught exception #1.", e);
}
catch
{
Console.WriteLine("Caught exception #2.");
}
finally
{
Console.WriteLine("Executing finally block.");
}
}
}
Sample Output Executing the try statement.
System.NullReferenceException: Object reference not set to an instance of an object.
at EHClass.Main() Caught exception #1.
Executing finally block.
40) Write C# program to illustrate exception handling a) for stack over flow b) divide by zero
exception
Example-2 using System;
class Program
{
static void Main()
{
try
{
int value = 1 / int.Parse("0");
Console.WriteLine(value);
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
www.csetube.in
www.csetu
be.in
18
18
}
}
}
The Program output
Attempt to divide by zero
41) Explain with an example how „DivideByZero‟ exception is handled in C#.
class ExceptionTest
{
static double SafeDivision(double x, double y)
{
if (y == 0)
throw new System.DivideByZeroException();
return x / y;
}
static void Main()
{
double a = 98, b = 0;
double result = 0;
try
{
result = SafeDivision(a, b);
Console.WriteLine("{0} divided by {1} = {2}", a, b, result);
}
catch (DivideByZeroException e)
{
Console.WriteLine("Attempted divide by zero.");
}
}
}
42) Define an array.
An array is a data structure that contains a number of subscripted variables. Each subscripted variable is
Known as an element of the array. All the elements are of the same data type.
An array is a reference data type in C#.
43) Explain array declaration and instantiation in C# with an example.
Syntax for array declaration
dataType[ ] arrayName; //declares a reference to an array
arrayName = new dataType[size]; // allocates memory
Example-1
Float[ ] x; // declaration of an array
X = new float[5]; // array has 5 elements
www.csetube.in
www.csetu
be.in
19
19
The first statement creates an one-dimensional array x. In the second statement , memory allocated
Using the new operator.
Example-2
Char[ ] str;
Str = new char[20];
Example-3
Int k = 25;
Float[] f;
F = new float[k];
44) Explain declaration and instantiation of a two dimensional array in C#.
Syntax for 2D array declaration ;
dataType [ , ] arrayName; // declaration of a 2D array
arrayName = new dataType[size1,size2]; // size1, and size2 are the no of rows
and no of columns resp.
Example-1
Int[ , ] s = new int[3,2]; // Defines a two-dimensional integer array a.
Example-2
Char[ , ] s = new char[10,20]; // 2D array to hold 200 elements
45) Write short notes on a) creation of three dimensional arrays b)creation of jagged arrays
The syntax for creating Three-dimensional array
dataType[ , , ] arrayName;
arrayName = new dataType[size1,size2,size3];
Example
Char[ , , ] book; // Declares a 3-dimensional array book
Book = new char[20, 40, 80]; // creates 3D array book
46) Tabulate the difference between regular and jagged arrays.
S. No Regular array Jagged array
1 Array of elements of non-array type Array of elements of array type
2 Multi dimensional array subscripts are
separated by comma within an open
and closing square brackets
Each array subscripts is enclosed
within separate square brackets
3 Shapes are regular Shapes are irregular
4 Declaration contains only one pair of
square brackets
Declaration contains two or more
pairs of square brackets
47) Differentiate „const‟ and „readonly‟ in C#.
www.csetube.in
www.csetu
be.in
20
20
const
A constant member is defined at compile time and cannot be changed at runtime. Constants are declared
as a field, using the const keyword and must be initialized as they are declared. For example;
public class MyClass
{
public const double PI = 3.14159;
}
PI cannot be changed in the application anywhere else in the code as this will cause a compiler error
readonly
A read only member is like a constant in that it represents an unchanging value. The difference is that a
readonly member can be initialized at runtime, in a constructor as well being able to be initialized as
they are declared. For example:
public class MyClass
{
public readonly double PI;
public MyClass()
{
PI = 3.14159;
}
}
48) What is ArrayList?
The main problem of traditional arrays is that their size is fixed by the number you specify when declaring
the array variable: you cannot add items beyond the specified dimension. Another limitation is that you
cannot insert an item inside the list.
To overcome this, you can create a linked list. Instead of working from scratch, the .NET Framework
provides the ArrayList class. With the ArrayList class, you can add new items to a list, insert items inside a
list, arrange items of a list, check the existence of an item in a list, remove an item from the list, inquire about
the list, or destroy the list. These operations are possible through various properties and methods.
The ArrayList class is defined in the System.Collections namespace.
EXAMPLE
using System.Collections;
class Program
{
static void Main()
www.csetube.in
www.csetu
be.in
21
21
{
//
// Create an ArrayList and add three elements.
//
ArrayList list = new ArrayList();
list.Add("One");
list.Add("Two");
list.Add("Three");
}
}
49) Differentiate an „array‟ and „arrayList‟ in C#.
C# : Difference between Array and Arraylist
System.Array System.Collections.ArrayList
1 Arrays are strongly typed.
That is all the elements have to be of the
same type. For example an array of integers
has to have all integers. It cannot have a
mix of integers and strings.
An arraylist is NOT strongly typed.
You can have a combination of built in types
(int,string etc) in your arraylist.
2 Cannot be dynamically resized.
(Note :Array.Resize() doesnot actually
resize the existing array. It infact creates a
new array with the required length and
copies values from the old array to new
array. Using the Resize is more memory
intensive than AddRange() in arraylist)
Can be dynamically resizedusing the method
Arraylist.AddRange()
3. Eg
int[] myIntArray = new int[2]
myIntArray[0]=10;
myIntArray[1]=20;
Eg
ArrayList leaderNames = new ArrayList();
leaderNames.Add("Obama");
leaderNames.Add(5);
www.csetube.in
