Advanced Web Programming

.NET Framework is a platform created by Microsoft for building, deploying, and running applications and services that use .NET technologies, such as desktop applications and Web services.

• It is a platform for application developers.
• It is a Framework that supports Multiple Language and Cross language integration.
• It has IDE (Integrated Development Environment).
• Framework is a set of utilities or can say building blocks of our application system.
• .NET Framework provides interoperability between languages i.e. Common Type System (CTS).
• .NET Framework also includes the .NET Common Language Runtime (CLR), which responsible for maintaining the execution of all applications developed using the .NET library.
• The .NET Framework consists primarily of a gigantic library of code.

Components of the .Net Framework:

User Interface and Program:

We can create various type of application using .net framework such as

• Console Application
• Windows Application
• Web application

Base class Library:

Base class library is one of component of .Net Framework. It supplies a library of base classes that we can use to implement applications quickly.

CLR (Common Language Runtime)

Common Language Runtime (CLR) is the programming (Virtual Machine component) that manages the execution of programs written in any language that uses the .NET Framework, for example C#, VB.Net, F# and so on.

We can say that it is heart and soul of .Net Framework or backbone

Explain CLR in detail.

• Common Language Runtime (CLR) is the programming (Virtual Machine component) that manages the execution of programs written in any language that uses the .NET Framework, for example C#, VB.Net, F# and so on.
• We can say that it is heart and soul of .Net Framework or backbone.
• Programmers write code in any language, including VB.Net, C# and F# then they compile their programs into an intermediate form of code called CLI in a portable execution file (PE) that can be managed and used by the CLR and then the CLR converts it into machine code to be will executed by the processor.
• The information about the environment, programming language, its version and what class libraries will be used for this code are stored in the form of metadata with the compiler that tells the CLR how to handle this code.
• The CLR allows an instance of a class written in one language to call a method of the class written in another language.

Components of the CLR:

CTS

Common Type System (CTS) describes a set of types that can be used in different .Net languages in common. That is, the Common Type System (CTS) ensure that objects written in different .Net languages can interact with each other. For Communicating between programs written in any .NET complaint language, the types must be compatible on the basic level.

These types can be Value Types or Reference Types. The Value Types are passed by values and stored in the stack. The Reference Types are passed by references and stored in the heap.

CLS

CLS stands for Common Language Specification and it is a subset of CTS. It defines a set of rules and restrictions that every language must follow which runs under .NET framework. The languages which follow these set of rules are said to be CLS Compliant. In simple words, CLS enables cross-language integration or Interoperability.

For Example if we take C-Sharp and VB.net in C# each statement must have to end with a semicolon it is also called a statement Terminator but in VB.NET each statement should not end with a semicolon (;). So, these syntax rules which we have to follow from language to language differ but CLR can understand all the language Syntax because in.NET each language is converted into MSIL code after compilation and the MSIL code is language specification of CLR.

It is language independent code. When you compile code that uses the .NET Framework library, we don't immediately create operating system - specific native code.

Instead, we compile our code into Microsoft Intermediate Language (MSIL) code. The MSIL code is not specific to any operating system or to any language.

Advantages:-

• MSIL provide language interoperability as code in any .net language is compiled on MSIL
• Same performance in all .net languages
• support for different runtime environments
• JIT compiler in CLR converts MSIL code into native machine code which is executed by OS

Functions of the CLR

• Garbage Collector
• Exception handling
• Type safety
• Memory management (using the Garbage Collector)
• Security
• Improved performance

What is namespace? How to create namespace and alias?

A namespace is designed for providing a way to keep one set of names separate from another. The class names declared in one namespace does not conflict with the same class names declared in another.

Defining a Namespace

A namespace definition begins with the keyword namespace followed by the namespace name as follows:

namespace namespace_name

{

// code declarations

}

Example:

using System;

namespace first_space

{

class namespace_cl

{

public void func()

{

Console.WriteLine("Inside first_space"); }

}

}

namespace second_space

{

class namespace_cl

{

public void func()

{

Console.WriteLine("Inside second_space");

}

}

}

class TestClass

{

static void Main(string[] args)

{

first_space.namespace_cl fc = new first_space.namespace_cl();

second_space.namespace_cl sc = new second_space.namespace_cl();

fc.func();

sc.func();

Console.ReadKey();

}

}

The using Keyword

The using keyword states that the program is using the names in the given namespace. For example, we are using the System namespace in our programs. The class Console is defined there. We just write:

Console.WriteLine ("Hello there");

We could have written the fully qualified name as:

System.Console.WriteLine("Hello there");

Alias of Namespace:

using A=System.Console;

class Test

{

static void Main()

{

A.Write("Craetion of Alias");

A.ReadKey();

}

Explain different types of data types in C#. OR Explain primitive and nonprimitive data types in C#

The data types in C# are categorized into the following types:

• Value types
• Reference types
• Pointer types

Value Type

Value type variables can be assigned a value directly. They are derived from the class System.ValueType.

The value types directly contain data. Some examples are int, char, and float, which stores numbers, alphabets, and floating-point numbers, respectively. When you declare an int type, the system allocates memory to store the value. Reference Type

The reference types do not contain the actual data stored in a variable, but they contain a reference to the variables.

In other words, they refer to a memory location. Using multiple variables, the reference types can refer to a memory location. If the data in the memory location is changed by one of the variables, the other variable automatically reflects this change in value. Example of built-in reference types are: object, dynamic, and string.

Explain the implicit and explicit conversion of data types with examples

The process of converting from one data type to another data type is called conversion.

Conversion can be 2 types as follows:

When one type of data is assigned to another type of variable, an implicit type conversion will take place automatically if

o The two types are compatible.

o The destination type has a range that is greater than the source type.

When these two conditions are met, a widening conversion takes place. For example, the int type is always large enough to hold all valid byte values, and both int and byte are compatible integer types, so an implicit conversion can be applied.

For widening conversions, the numeric types, including integer and floating-point types, are compatible with each other.

For example, the following program is perfectly valid since long to double is a widening conversion that is automatically performed.

using System;

class LtoD

{

static void Main()

{

long L; double D;

L = 100123285L;

D = L;

Console.WriteLine("L and D: " + L + " " + D);

}

}

Casting Incompatible Types

Although the implicit type conversions are helpful, they will not fulfil all programming needs because they apply only to widening conversions between compatible types. For all other cases we must employ a cast. A cast is an instruction to the compiler to convert the outcome of an expression into a specified type. Thus, it requests an explicit type conversion.

A cast has this general Form:

(target-type) expression

Here, target-type specifies the desired type to convert the specified expression to. For

Example

double x, y;

if you want the type of the expression x/y to be int, you can write (int)(x/y)

Here, even though x and y are of type double, the cast converts the outcome of the expression to int. The parentheses surrounding x / y are necessary. Otherwise, the cast to Int would apply only to the x and not to the outcome of the division.

The cast is necessary here because there is no implicit conversion from double to int. When a cast involves a narrowing conversion, information might be lost.

Explain Boxing and Unboxing with reference to value type and reference type.

Boxing:

Any type, value or reference can be assigned to an object without explicit conversion. When a compiler fined a value where it needs a reference type, it creates an object ‘box’ into which it places the value of the value type. Example: - int m = 10; object om = m;

When executed, this code creates a temporary reference _type ‘box’ for the object on heap. We can also use a C-style cast for boxing.

int m = 10;

object om = (object) m;

Note that the boxing operation creates a copy of the value of the m integer to the object om. Both the variables exist but the value of om resides on the heap. This means that the values are independent of each other.

Example

int m =10; object om = m; m = 20;

Console.WriteLine(m); // m= 20

Console .WriteLine(om); //om=10

Unboxing:

Unboxing is the process of converting the object type back to the value type. Remember that a variable can be unboxed only if it has been previously boxed. In contrast to boxing, unboxing is an explicit operation.

Example:-

int m = 100;

object om = m; //boxing

int n = (int) om; //unboxing

When performing unboxing, C# checks the value type we request is actually stored in the object under conversion. Only if it is, the value is unboxed.

List and explain the comparison and logical operators in C#.

Comparison operators:

It is also called as relational operator. They are used to compare at least two operands.

Below is the list of relational operators as follows:

Logical operators

Logical operators are used to combine two or more condition. Below is list of logical operators used in C#.

Explain flow control, explain what is break and continue statement

The statements inside your source files are generally executed from top to bottom, in the order that they appear. Control flow statements, however, break up the flow of execution by employing decision making, looping, and branching, enabling your program to conditionally execute particular blocks of code.

Break Statement

The break statement is used to exit from loops and switch statements. The break statement terminates the execution control from a loop or a switch statement to the next statement after the loop or switch statement.

The general format is:

Example:-Write a program to generate the following triangle

1

1 2

1 2 3

using System; class demo

{

public static void Main()

{

for(int i=1;i<=5;i++)

{

for(int j=1;j<=5;j++)

{

Console.Write(" "+j); if(j==i)

{

break;

}

}

Console.WriteLine(" ");

}

}

}

Continue Statement

The continue statement causes early iteration of a loop. It skips the remaining statements after the continue statement and moves the execution control to the next iteration of the loop.

The general format is:

using System; class demo

{

public static void Main()

{

for(int i=1;i<=25;i++)

{

if(i%2!=0)

{

continue;

}

else

Console.Write(" "+i);

} }

}

Use the break keyword to stop the loop and the continue keyword to skip one loop cycle and continue to the next.

using System;

public class Program

{

public static void Main()

{

Console.WriteLine("Demonstrating the use of break.\n");

for (int x = 1; x < 10; x++)

{

if (x == 5) break;

Console.WriteLine("Number " + x);

}

Console.WriteLine("\nDemonstrating the use of continue.\n");

for (int x = 1; x < 7; x++)

{

if (x == 5)

continue;

Console.WriteLine("Number " + x);

} }

}//code end here

Demonstrating the use of break.

Number 1

Number 2

Number 3

Number 4

Demonstrating the use of continue.

Number 1

Number 2

Number 3

Number 4

Number 6

Give general form of switch statement. Explain with example.

The switch statement is similar to if statement in that it executes code conditionally based on the value of a test. However, switch enables us to test for multiple values of a test variable in one go, rather than just a single condition.

This test is limited to discrete values, rather than clauses such as ‘‘greater than X,’’ so its use is slightly different; but it can be a powerful technique.

The basic structure of a switch statement is as follows:

switch (<testVar>)

{

case<comparisonVal1>:

<code to execute if <testVar> == <comparisonVal1>>

break;

case<comparisonVal2>:

<code to execute if <testVar> == <comparisonVal2>>

break;

. . . case<comparisonValN>:

<code to execute if <testVar> == <comparisonValN>>

break;

default:

<code to execute if <testVar> != comparisonVals> break;

}

Example:

class SwitchEg

{

static void Main(string[] args)

{

const string myName = "karli";

const string sexyName = "angelina";

const string sillyName = "ploppy";

string name;

Console.WriteLine("What is your name?");

name = Console.ReadLine();

switch (name.ToLower())

{

case myName:

Console.WriteLine("You have the same name as me!");

break;

case sexyName:

Console.WriteLine("My, what a sexy name you have!");

break;

case sillyName: Console.WriteLine("That’s a very silly name.");

break;

}

Console.WriteLine("Hello {0}!", name);

Console.ReadKey();

}

}

Give syntax of foreach loop. Explain with example.

A foreach loop mostly used with array and collection such ArrayList. A foreach loop enables us to address each element in an array using this simple syntax:

foreach (<baseType><name> in <array>)

{

// can use <name> for each element

}

This loop will cycle through each element, placing it in the variable <name> in turn, without danger of accessing illegal elements. We don’t have to worry about how many elements are in the array, and we can be sure that we get to use each one in the loop.

The main difference between using this method and a standard for loop is that foreach gives us read-only access to the array contents, so we can’t change the values of any of the elements. Example

using System;

class Abc

static void Main(string[] args)

{

string[] friendNames = { "Robert Barwell", "Mike Parry", "Jeremy Beacock" };

Console.WriteLine("Here are {0} of my friends:", friendNames.Length);

foreach (string friendName in friendNames)

{

Console.WriteLine(friendName);

}

Console.ReadKey();

}

Difference between for and foreach loop

A for loop executes a statement or a block of statements repeatedly until a specified expression evaluates to false. There is need to specify the loop bounds (minimum or maximum).

Example:

int j = 0;

for(int i=1;i<=5;i++)

{

j= j + i ;

}

The foreach statement repeats a group of embedded statements for each element in an array or an object collection. You do not need to specify the loop bounds minimum or maximum.

Example:

int j = 0;

int[] tempArr = new int[] { 0, 1, 2, 3, 5, 8, 13 };

foreach (int i in tempArr )

{

j = j + i ;

}

Explain variable sized array with suitable example. OR Explain jagged array with example.

Jagged array is also called Array of Array or variable sized array. In a jagged array, each row may have different number of columns.

It is equivalent to an array of variable sized one-dimensional arrays. The Length property is used to get the length of each one-dimensional array.

A jagged array can be declared and initialized as follows:

datatype[][] arrayname=new datatype[rowsize][];

arrayname[0]=new datatype[]{val1,val2,val3, …};

arrayname[1]=new datatype[]{val1,val2,val3, …};

arrayname[2]=new datatype[]{val1,val2,val3, …};

Example:-

class numadd

{

public static void Main()

{

int[][] x=new int[4][];

x[0]=new int[2]{5,13};

x[1]=new int[3]{7,8,11};

x[2]=new int[4]{2,3,4,5};

x[3]=new int[1]{9};

for(int i=0;i<4;i++)

{

for(int j=0;j<x[i].Length;j++)

{

Console.Write(x[i][j]+"\t");

}

Console.Write("\n");

}

}

Explain ref parameter and out parameter

Reference Parameter:

It is used as a call by reference in C#. It is used in both places; when we declare a method and when we call the method. In this example we create a function (cube) and pass a ref parameter in it, now we look at the value before we call the function and after we call the function.

classAbc

{

public void cube(ref int x)

{

x= x * x * x;

}

}

class Program

{

static void Main(string[] args)

{

TryRef tr = new TryRef();

int y = 5;

Console.WriteLine("The value of y before the function call: " + y);

tr.cube(ref y);

Console.WriteLine("The value of y after the function call: " + y);

Console.ReadLine();

}

}

Output Parameter:

Sometimes we do not want to give an initial value to the parameter; in this case we use the out parameter. The declaration of the out parameter is the same as the ref parameter. But it is used to pass the value out of a method. Now we look at the:

classAbc

{

public int mul(int a, out int b)

{

b = a * a; return b;

}

}

class Program

{

static void Main(string[] args)

{

tryout to = new tryout(); int x,y;

x = to.mul(10, out y);

Console.WriteLine("The output is: "+x);

Console.ReadLine();

}

}

Is Multiple Main () allowed in C#? Justify

We can use more than on Main Method in C# program, But there will only one Main Method which will act as entry point for the program.

using System; class A

{

static void Main(string[] args)

{

Console.WriteLine("I am from Class A");

Console.ReadLine();

}

}

class B

{

static void Main(string[] args)

{

Console.WriteLine("I am from Class B");

Console.ReadLine();

}

}

Try to execute Program as given below:

csc filename.cs /main:classname

As in given program there are two classes A and B in which each containing A Main Method.

We may write as.

csc filename.cs /main:A [ for Class A Main Execution ] or,

csc filename.cs /main:B [ for Class B Main Execution]

Need of enumerator data type in C#

• An enum is a value type with a set of related named constants often referred to as an enumerator list.
• The enum keyword is used to declare an enumeration. It is a primitive data type, which is user defined.
• Enums type can be integer (float, int, byte, double etc.). But if you used beside int it has to be cast.
• The keyword enum is used to create numeric constants in .NET framework.
• There must be a numeric value for each enum type.
• The default underlying type of the enumeration elements is int. By default, the first enumerator has the value 0, and the value of each successive enumerator is increased by 1.

Example:-

using System;

enumDays {Sat, Sun, Mon, Tue, Wed, Thu, Fri};

class Abc

{

public static void main()

{

Console.WriteLine((int)Days.Wed);

Console.WriteLine((Days)4);

}

}

Explain inheritance and polymorphism.

Inheritance

Inheritance is the concept we use to build new classes using the existing class definitions. Through inheritance we can modify a class the way we want to create new objects. The original class is known as base or parent class & the modified class is known as derived or subclass or child class. The concept of inheritance facilitates the reusability of existing code & thus improves the integrity of programs & productivity of programmers.

Polymorphism.

Polymorphism is the ability to take more than one form. For example, an operation may exhibit different behavior in different situations. The behavior depends upon the types of data used on the operation. Polymorphism is extensively used while implementing inheritance.

Two types

Compile time polymorphism

Runtime time polymorphism

What are sealed classes and sealed methods? Why are they used?

The methods declared with a sealed keyword in its header are known as sealed methods. Such method provides a complete implementation to its base class virtual method using the override keyword.

Characteristics

A method cannot be defined as sealed unless that method is an override of a method in its base class.

A sealed method cannot be overridden further.

Sealed methods are useful to avoid problems caused by overriding the existing functionality. It prevents the user from changing the internal functionality of a class.

Example:

using system; class A

{

public virtual void F()

{

Console.WriteLine("A.F");

}

public virtual void G()

{

Console.WriteLine("A.G");

}

}

class B: A

{

sealed override public void F()

{

Console.WriteLine("B.F");

}

override public void G()

{

Console.WriteLine("B.G");

}

}

class C: B

{

override public void G()

{

Console.WriteLine("C.G");

}

}

The class B provides two override methods: an F method that has the sealed modifier and a G method that does not. B's use of the sealed modifier prevents C from further overriding F.

Sealed Classes:

Generally if we create classes we can inherit the properties of that created class in any class without having any restrictions.

In some situation we will get requirement like we don’t want to give permission for the users to derive the classes from it or don’t allow users to inherit the properties from particular class.

For that purpose we have keyword called “sealed” in OOPS.

When we defined class with keyword “Sealed” then we don’t have a chance to derive that particular class and we don’t have permission to inherit the properties from that particular class.

A sealed class cannot be inherited.

It is an error to use a sealed class as a base class.

Use the sealed modifier in a class declaration to prevent inheritance of the class. It is not permitted to use the abstract modifier with a sealed class.

Example:

using System;

sealed class MyClass

{

public int x;

public int y;

}

class MainClass

{

public static void Main()

{

MyClass mC = new MyClass();

mC.x = 110;

mC.y = 150;

Console.WriteLine("x = {0}, y = {1}", mC.x, mC.y);

}

}

What are the rules in defining a constructor? Explain static constructor with example.

Rules for constructor:

A constructor should have the same name as that of its class.

Constructors can take any number of arguments.

Constructor cannot return any value.

A static constructor is used to initialize static variables of a class. It is declared using the static keyword. A class can have only one static constructor.

Static Constructor:

The general syntax of a static constructor is shown below.

static classname()

{

//static member initializations;

}

Also note that a static constructor is parameter less and no access modifiers are allowed with its declaration. The exact timing of static constructor execution is implementationdependent, but is subject to the following rules:

The static constructor for a class executes before any instance of the class is created.

The static constructor for a class executes before any of the static members for the class are referenced.

The static constructor for a class executes after the static fields initializes for the class. The static constructor for a class executes at most one time during a single program execution.

Example:

class A

{

static A()

{

Console.WriteLine("static constructor A is invoked");

}

public static void Main()

{ } }

Explain various Types of Constructors in C#

Default and Parameterized

• When constructor does not accept any parameter then it is referred as default constructor or zero parametrized.
• When constructor accepts the parameter then it is referred as parametrized constructor.

Example:

using System;

class test

{

double length,breadth;

Public test()

{

Console.WriteLine("default cons");

}

public test(double l, double b)

{

Console.WriteLine("paramaterized cons");

length = l; breadth = b;

}

public double area()

{

return (length * breadth);

}

}

class testmain

{

public static void Main()

{

test defaultcon =new test();//calls default cons

test t1 = new test(10.05, 100.45);

double result = t1.area();

Console.WriteLine("area of rectangle-->" + result);

Console.ReadLine();

}

}

Private constructor

• Private constructors are used to restrict the instantiation of object using ‘new’ operator.
• A private constructor is a special instance constructor. It is commonly used in classes that contain static members only.
• This type of constructors is mainly used for creating singleton object.
• If you don't want the class to be inherited we declare its constructor private.

Example:

using System;

class test

{

private test()

{

Console.WriteLine("private cons ");

}

public test(int x)

{

Console.WriteLine("non private cons--->"+ x);

}

}

class testmain

{

public static void Main()

{

test t1 = new test();//Error'test.test()' is inaccessible due to its protection level

test t2 = new test(10);

Console.ReadLine();

} }

Static Constructor

• There can be only one static constructor in the class.
• The static constructor should be without parameters.
• It can only access the static members of the class.
• There should be no access modifier in static constructor definition.

Example:

using System;

class test

{

static int x;

static test()

{

Console.WriteLine("static cons ");

x = 10;//set the values for static member here

}

public static void show()

{

Console.WriteLine("show of x--->" + x);

}

}

class testmain

{

public static void Main()

{

test.show();

Console.ReadLine();

} }

Copy Contructor

When constructor accepts the object as parameter then it is referred as copy constructor.

Example:

using System; class test

{

double length, breadth;

public test()

{

Console.WriteLine("default cons");

}

public test(double l, double b)

{

//Console.WriteLine("paramaterized cons");

length = l; breadth = b;

}

public test(test t1)

{

length = t1.length;

breadth = t1.breadth;

}

public double area()

{

return (length * breadth);

} }

class testmain

{

public static void Main()

{

test defaultcon = new test();//calls default cons

test t1 = new test(10,10);

double result = t1.area();

Console.WriteLine("area of rectangle t1-->" + result);

test t2 = new test(20, 20);

double result1 = t2.area();

Console.WriteLine("area of rectangle t2-->" + result1);

test t3 = new test(t2);

double result_copy = t3.area();

Console.WriteLine("area of rectangle t3 is copy_con of t2-->" + result_copy); Console.ReadLine();

}

}

How multiple inheritance achieved using interfaces?

C# does not support multiple inheritance. However, you can use interfaces to implement multiple inheritance. The following program demonstrates this:

Example:

using System;

class Shape

{

public void setWidth(int w)

{

width = w;

}

public void setHeight(int h)

{

height = h;

}

protected int width;

protected int height;

}

public interface PaintCost

{

int getCost(int area);

}

class Rectangle : Shape, PaintCost

{

public int getArea()

{

return (width * height);

}

public int getCost(int area)

{

return area * 70;

} }

class RectangleTester

{

static void Main(string[] args)

{

Rectangle Rect = new Rectangle();

int area;

Rect.setWidth(5);

Rect.setHeight(7);

area = Rect.getArea();

Console.WriteLine("Total area: {0}", Rect.getArea());

Console.WriteLine("Total paint cost: ${0}" , Rect.getCost(area));

Console.ReadKey();

}

}

}

When is explicit interface necessary?

• C# does not support multiple inheritances, but a class has the option of implementing one or more interfaces.
• One challenge with interfaces is that they may include methods that have the same signatures as existing class members or members of other interfaces.
• Explicit interface implementations can be used to disambiguate class and interface methods that would otherwise conflict.
• Explicit interfaces can also be used to hide the details of an interface that the class developer considers private.
• To explicitly implement an interface member, just use its fully qualified name in the declaration.
• A fully qualified interface name takes the form InterfaceName.MemberName

Example:

interface I1

{

void A();

}

interface I2

{

void A();

}

class C : I1, I2

{

public void I1.A()

{

Console.WriteLine("A() from I");

}

void I2.A()

{

Console.WriteLine("A() from I2");

}

}

Explain the similarities and differences between Interfaces and Abstract classes

Similarities:

• Both abstract classes and interfaces may contain members that can be inherited by a derived class.
• Neither interfaces nor abstract classes may be directly instantiated, but we can declare variables of these types. If we do, we can use polymorphism to assign objects that inherit from these types to variables of these types.
• In both cases, we can then use the members of these types through these variables, although we don’t have direct access to the other members of the derived object.

Differences:

• Derived classes may only inherit from a single base class, which means that only a single abstract class can be inherited directly. Conversely, classes can use as many interfaces as they want
• Abstract classes may possess both abstract members and non-abstract members. Interface members conversely, must be implemented on the class that uses the interface they do not possess code bodies.
• Moreover, interface members are by definition public but members of abstract classes may also be private (as long as they aren’t abstract), protected, internal, or protected internal. In addition, interfaces can’t contain fields, constructors, destructors, static members, or constants.

Explain method overriding with example

• Method overriding in C# is achieved through inheritance.
• If a class is inherited by a derived class, then the derived class can override the base class method. This concept is termed as Method Overriding.
• Method Overriding is implemented in C# using the keywords virtual and override. The base class method that has to be overridden must be marked as virtual or abstract (if the base class is an abstract class).
• The derived class method that overrides the base class method should be marked with the keyword override.

Example:

Class A;

{

public virtual void Test()

{

Console.WriteLine("A::Test()");

}

}

class B : A

{

public override void Test()

{

Console.WriteLine("B::Test()");

}

}

class C : B

{

public override void Test()

{

Console.WriteLine("C::Test()");

}

}

class Program

{

static void Main(string[] args)

{

A a = new A();

B b = new B();

C c = new C();

a.Test(); // output --> "A::Test()"

b.Test(); // output --> "B::Test()"

c.Test(); // output --> "C::Test()"

a = new B();

a.Test(); // output --> "B::Test()"

b = new C();

b.Test(); // output --> "C::Test()"

Console.ReadKey();

}

}

Differentiate Overloading and Overriding

Overloading

• Method Overloading means having two or more methods with the same name but with different signature (different parameters list and different type of parameters) in same class or in different classes. Method Overloading forms compile-time polymorphism.

Overriding

• Method overriding means having two methods with same name and same signature, one method in base class and other method in derived class.
• A subclass inherits methods from a base class. Sometimes, it is necessary for the subclass to modify the methods defined in the base class. This is referred to as method overriding.
• This can be achieved by using the virtual and override keywords. We have to use the virtual keyword for the method which in base class and override keyword for the method in subclass.
• By default functions are not virtual in C# and so you need to write “virtual” explicitly.

Explain method hiding with example.

In a C# program a derived class can have methods with the same signature as that of its base class methods. This hides the base class methods by its derived class counterparts and gives a warning.

This warning can be suppressed by using the new keyword with the derive class methods. This means that the members of the base class are made intentionally hidden by the members having the same signature in the derived class. The new function will never be invoked by a base class pointer.

Example:-

class demo

{

public void disp()

{

System.Console.WriteLine("From disp method of base class");

}

}

class test:demo

{

new public void disp()

{

System.Console.WriteLine("From disp method of derived class");

}

public static void Main()

{

test t=new test();

t.disp();

}

}

What is the difference between overriding methods and hiding methods?

Overriding methods:

• In method overriding we can override a method in base class by creating similar method in derived class this can be achieved by using inheritance principle and using “virtual & override” keywords.
• If we want to override base class method then we need to declare base class method with “virtual” keyword and the method which we created in derived class to override base class need to declare with “override” keyword like as shown below

Example:-

class SampleA

{

public virtual void Show()

{

Console.WriteLine("Sample A Test Method");

}

}

class SampleB:SampleA

{

public override void Show()

{

Console.WriteLine("Sample B Test Method");

}

}

class Program

{

static void Main(string[] args)

{

SampleA a=new SampleA();

SampleB b=new SampleB();

a.Show();

b.Show();

a = new SampleB();

a.Show();

Console.ReadLine();

}

}

}

Hiding methods:

To hide base class methods in derived classes we can declare derived class methods with new keyword. To use new keyword, we need to write the code like as shown below

Example:-

class SampleA

{

public void Show()

{

Console.WriteLine("Sample A Test Method");

}

}

class SampleB:SampleA

{

public new void Show()

{

Console.WriteLine("Sample B Test Method");

}

}

class Program

{

static void Main(string[] args)

{

SampleA a=new SampleA();

SampleB b=new SampleB();

a.Show();

b.Show(); a = new

SampleB(); a.Show();

Console.ReadLine();

}

}

Define each of the following terms:

Derived class

The functionality of an existing class can be extended by creating a new class from it. The new class is then called a child class or derived class. The derived class inherits the properties of the base class.

Abstract class

An Abstract class is a non-instantiable class which is either partially implemented, or not at all implemented. It can have abstract methods as well as non-abstract methods. Abstract classes require subclasses to provide implementations for the abstract methods. It provides default functionality to its sub classes.

Static class

A static class is class whose objects cannot be created and must contain only static members.

Sealed class

A sealed class is a class which cannot be inherited. In C#, the sealed modifier is used to define a class as sealed.

Partial class

It is possible to split the definition of a class over two or more source files. Each source file contains a section of the type or meth

Write a short note on Assembly.

• An assembly in ASP.NET is a collection of single-file or multiple files. The assembly that has more than one file contains either a dynamic link library (DLL) or an EXE file. The assembly also contains metadata that is known as assembly manifest.
• The assembly manifest contains data about the versioning requirements of the assembly, author name of the assembly, the security requirements that the assembly requires to run, and the various files that form part of the assembly.
• The biggest advantage of using ASP.NET Assemblies is that developers can create applications without interfering with other applications on the system. When the developer creates an application that requires an assembly that assembly will not affect other applications.
• The assembly used for one application is not applied to another application. However, one assembly can be shared with other applications. In this case the assembly has to be placed in the bin directory of the application that uses it.
• This is in contrast to DLL in the past. Earlier developers used to share libraries of code through DLL. To use the DLL that is developed by another developer for another application, we must register that DLL in our machine. In ASP.NET, the assembly is created by default whenever we build a DLL. We can check the details of the manifest of the assembly by using classes located in the System.Reflection namespace.
• Thus, we can create two types of ASP.NET Assemblies in ASP.NET: private ASP.NET Assemblies and shared assemblies. Private ASP.NET Assemblies are created when you build component files like DLLs that can be applied to one application.
• Shared ASP.NET Assemblies are created when you want to share the component files across multiple applications. Shared ASP.NET Assemblies must have a unique name and must be placed in Global Assembly Cache (GAC). The GAC is located in the Assembly directory in WinNT.
• You can view both the manifest and the IL using ILDisassembler (ildasm.exe).

List and Explain the Components of assemblies.

An assembly is a fundamental building block of any .NET framework application. It contains the code that is executed by common language runtime. For example, when we build a simple C# application, Visual Studio creates an assembly in the form of a single portable executable (PE) file, specifically an EXE or DLL.

Every assembly has a file called ‘manifest’ file that stores all information about that assembly. This information’s are known as metadata.

The manifest file contains all the metadata needed to specify the assembly's version requirements, security identity, and all metadata needed to define the scope of the assembly and resolve references to resources and classes.

Components of Assembly

Manifest

It describes the assembly. The manifest file contains all the metadata needed to specify the assembly's version requirements, security identity, and all metadata needed to define the scope of the assembly and resolve references to resources and classes.

Type Metadata

It contains metadata, which describes each type (class, structure, enumeration, and so forth)

MSIL

It contains Intermediate language code.

Resources

It contains bitmaps, icons, audios and other types of resources.

Difference between public assembly and private assembly

ArrayList is a non-generic type of collection in C#. It can contain elements of any data types. It is similar to an array, except that it grows automatically as you add items in it. Unlike an array, we don't need to specify the size of ArrayList.

Example: Initialize ArrayList

ArrayList myArryList = new ArrayList();

Properties and Methods of ArrayList

Presentation Layer

The presentation layer consists of the Asp.net page that manages the appearance of application. This layer can include bound data controls and ObjectDataSource objects that bind data controls to the data.

Middle Layer

The middle layer contains the data access classes that manage the data access for the application. This layer can also contain business objects that represent business entities such as customers, products or employee and that implement business rules such as credit and discount policies.

Database Layer

This layer consists of the database that contains the data for the application. Ideally the SQL statement that do the database access should be saved in stored procedure within the database, nut the SQL statement are often stored in the data access classes.

ASP.NET life cycle specifies, how:

ASP.NET processes pages to produce dynamic output

The application and its pages are instantiated and processed

ASP.NET compiles the pages dynamically

When a page is requested, it is loaded into the server memory, processed and sent to the browser. Then it is unloaded from the memory. At each of this steps, methods and events are available, which could be overridden according to the need of the application

This is an input control which is used to take user input. To create TextBox either we can write code or use the drag and drop facility of visual studio IDE.

This is server side control, asp provides own tag to create it. The example is given below.

< asp:TextBoxID="TextBox1" runat="server" ></asp:TextBox>

This control has its own properties that are tabled below.

Text

It is used to set text to be shown for the control.

MaxLength

It is used to set maximum number of characters that can be entered.

Readonly

It is used to make control readonly.

TextMode

It used to determine behavior of control. Possible value are Single / Multiline / Password

CausesValidation

true/false – It is used to enable or disable validation effect on control

Example:

Assign a text to TextBox control when Button click event fires using c#

These controls differ only in how they appear to the user. A button displays text within a rectangular area. A Link button displays text that look like a hyperlink and an image button displays an image.

LinkButton control is a control just like a Button control along with the flexibility to make it look like a Hyperlink. It implements an anchor <a/> tag that uses only ASP.NET postback mechanism to post the data on the server. Despite being a hyperlink, we can't specify the target URL.

ImageButton control is used to post the form or fire an event either client side or server side. It’s like a asp:Button control, the only difference is, we have the ability to place our own image as a button.

ImageButton control is generally used to post the form or fire an event either client side or server side.

Button control is used to post the form or fire an event either client side or server side. Button control is generally used to post the form or fire an event either client side or server side. When it is rendered on the page, it is generally implemented through <input type=submit> HTML tag.

CheckBox:

CheckBox control is an asp.net web server control. CheckBox control visually as square on web forms. The Checkbox control allow user to check square or uncheck square.

In CheckBox control check and uncheck checkbox specify by the checked property of check box true or false. Basic syntax for check box:

<asp:CheckBox ID= "chkoption" runat= "Server">

</asp:CheckBox>

CheckBox properties:

AutoPostBack:Specifies whether the form should be posted immediately after the Checked property has changed or not. Default is false

CausesValidation:Specifies if a page is validated when a Button control is clicked

Checked:Specifies whether the check box is checked or not

Id:A unique id for the control

Text: The text next to the check box

Event:

OnCheckedChanged

The name of the function to be executed when the checked property has changed

RadioButton

Radiobutton isasp.net web server control. Radiobutton is used to allow user to select a single radiobutton from group of radiobutton. In asp.net generally we use more than one radiobutton and select only one radiobutton at a time from all the radiobutton control. On other hand in checkbox control we can check and uncheck multiple check box at a time.

Basic syntax for radio button:

<asp:RadioButton ID= "rdboption" runat= "Server"></asp:

RadioButton>

RadioButton properties:

AutoPostBack:A Boolean value that specifies whether the form should be posted immediately after the Checked property has changed or not. Default is false

Checked : A Boolean value that specifies whether the radio button is checked or not id a unique id for the control

GroupName : The name of the group to which this radio button belongs

Text :The text next to the radio button

The basic syntax of adding an AdRotator is as follows:

<asp:AdRotator runat = "server" AdvertisementFile = "adfile.xml" />

The advertisement file is an XML file, which contains the information about the advertisements to be displayed.

There are the following standard XML elements that are commonly used in the advertisement file:

The Calendar control when rendered to a user browser, it generates an HTML <table> element and a set of associated JavaScript. The Calendar control can be used to select a single date or multiple dates. The SelectionMode property is used for this.

The SelectionMode properties are as:

Example:

In this below example we will simply check the length of the string in the TextBox.

Custom Text:<br />

<asp:TextBox runat="server"

id="txtCustom" />

<asp:CustomValidator

runat="server" id="cusCustom" controltovalidate="txtCustom" onservervalidate="cusCustom_ServerValidate" errormessage="The text must be exactly 8 characters long!" />

<br /><br />

protected void cusCustom_ServerValidate(object sender, ServerValidateEventArgs e)

{

if(e.Value.Length == 8)

e.IsValid = true;

else

e.IsValid = false;

}

Explain Menu control in ASP.NET

The Menu control is used to create a menu of hierarchical data that can be used to navigate through the pages. The Menu control conceptually contains two types of items. First is StaticMenu that is always displayed on the page, second is DynamicMenu that appears when opens the parent item.

Following steps are used to create Menu Control:

Toolbox > Navigation > Menu or add the following few lines of code snippet.

<asp:Menu ID="Menu1" runat="server"

Orientation="Horizontal">

<Items>

<asp:MenuItem Text="HOME" NavigateUrl="~/Default.aspx"

Selected="true" />

<asp:MenuItem Text="HTML"

NavigateUrl="~/HTML.aspx">

<asp:MenuItem

Text="HtmlTagList"

NavigateUrl="~/HtmlTagList.aspx" />

</asp:MenuItem>

<asp:MenuItem Text="CSS"

NavigateUrl="~/CSS.aspx">

<asp:MenuItem Text="CssSelectors" NavigateUrl="~/CssSelectors.aspx" />

</asp:MenuItem>

</Items>

</asp:Menu>

Below are the various Properties of Menu Control

When to use TreeView control in ASP.NET

ASP.NET TreeView Web control is used to display hierarchical data (such as a table of contents) in a tree structure in a Web page.

The TreeView control is made up of TreeNode objects. The TreeView control can be bound to data.

It supports the following features:

Automatic data binding, this allows the nodes of the control to be bound to hierarchical data, such as an XML document.

Site navigation support through integration with the SiteMapDataSource control.

Node text that can be displayed as either selectable text or hyperlinks.

Customizable appearance through themes, user-defined images, and styles.

Programmatic access to the TreeView object model, which allows you to dynamically create trees, populates nodes, set properties, and so on.

Node population through client-side callbacks to the server (on supported browsers).

The ability to display a check box next to each node.

<asp:TreeView ExpandDepth="1" runat="server">

<Nodes>

<asp:TreeNode Text="Employees">

<asp:TreeNode Text="Bradley" Value="ID-1234" />

<asp:TreeNode Text="Whitney" Value="ID-5678" />

<asp:TreeNode Text="Barbara" Value="ID-9101" />

</asp:TreeNode>

</Nodes>

</asp:TreeView>

Each node in the Tree is represented by a name/value pair (not necessarily unique), defined by the Text and Value properties of TreeNode, respectively. The text of a node is rendered, whereas the value of a node is not rendered and is typically used as additional data for handling postback events.

This example also uses the ExpandDepth property of TreeView to automatically expand the tree 1 level deep when it is first rendered.

The TreeView control is made up of one or more nodes. Each entry in the tree is called a node and is represented by a TreeNode

Explain SiteMapPath control in ASP.NET

The SiteMapPath control basically is used to access web pages of the website from one webpage to another. It is a navigation control and displays the map of the site related to its web pages.

This map includes the pages in the particular website and displays the name of those pages. We can click on that particular page in the Site Map to navigate to that page. We can say that the SiteMapPath control displays links for connecting to URLs of other pages.

The SiteMapPath control uses a property called SiteMapProvider for accessing data from databases and it stores the information in a data source.

The representation of the SiteMapPath control is as follows:

Root Node->Child Node

Following steps are used to create Menu Control:

Toolbox > Navigation >SiteMapPath

Following are some important properties that are very useful.

ParentLevelsDisplayed :

It specifies the number of levels of parent nodes and then displays the control accordingly related to the currently displayed node.

RenderCurrentNodeAsLink :

It specifies whether or not the site navigation node that represents the currently displayed page is rendered as a hyperlink.

PathSeperator :

It specifies the string that displays the SiteMapPath nodes in the rendered navigation path.

Style properties of the SiteMapPath class

CurrentNodeStyle :

It specifies the style used for the display text for the current node.

RootNodeStyle :

It specifies the style for the root node style text.

NodeStyle :

It specifies the style used for the display text for all nodes in the site navigation path.

Sitemap file has been included in our project and we can see it in the Solution Explorer. And now we have to set the URL and title attributes in the sitemap file.

<?xml version="1.0" encoding="utf-8" ?>

<siteMap xmlns="http://schemas.microsoft.com/AspNet/SiteMap- File-1.0" > <siteMapNode url="Default.aspx" title="myhomepage" description="">

<siteMapNode url="myweb1.aspx" title="myfirstpage" description="" />

<siteMapNode url="myweb2.aspx" title="mysecondpage" description="" /> </siteMapNode>

</siteMap>

Difference between Structures and Classes.

It provides the following information at the top:

• Session ID

• Status Code

• Time of Request

• Type of Request

• Request and Response Encoding

The status code sent from the server, each time the page is requested shows the name and time of error if any. The following table shows the common HTTP status codes: The class of a status code can be quickly identified by its first digit:

1xx: Informational

2xx: Success

3xx: Redirection

4xx: Client Error

5xx: Server Error

When debugging is enabled, the following lines of codes are shown in the web.config:

<system.web>

<compilation debug="true">

<assemblies>

..............

</assemblies>

</compilation>

</system.web>

The Debug toolbar provides all the tools available for debugging:

Breakpoints

Breakpoints specifies the runtime to run a specific line of code and then stop execution so that the code could be examined and perform various debugging jobs such as, changing the value of the variables, step through the codes, moving in and out of functions and methods etc.

To set a breakpoint, right click on the code and choose insert break point. A red dot appears on the left margin and the line of code is highlighted as shown:

Next when you execute the code, you can observe its behavior.

At this stage, you can step through the code, observe the execution flow and examine the value of the variables, properties, objects, etc.

We can modify the properties of the breakpoint from the Properties menu obtained by right clicking the breakpoint glyph:

Application State:

§ If the information that we want to be accessed or stored globally throughout the application, even if multiple users access the site or application at the same time, then we can use an Application Object for such purposes.

§ It stores information as a Dictionary Collection in key - value pairs. This value is accessible across the pages of the application / website.

§ There are 3 events of the Application which are as follows

Application_Start

Application_Error

Application_End

Example - Just for an example, I am setting the Page title in the Application Start event of the Global.asax file.

Code for setting value to the Application Object - "PageTitle" is the Key and "Welcome to State Management Application" is the value.

Code for reading value from the Application Object

After adding the theme folder, add the SkinFile.skin file by right-clicking on the ASP.Net theme folder. The Solution Explorer will then look as follows:

Now add the ASP.Net controls inside the SkinFile.Skin and assign the Style to the controls using their properties as in the following

1. A control Id cannot be assigned to ASP.Net controls inside the SkinFile.skin.

2. SkinId must be assigned to the ASP.Net controls inside the SkinFile.skin.

3. The SkinId should be uniquely defined because duplicate SkinId's per control type are not allowed in the same theme. 4. Only one default control skin per control type is allowed in the same theme.

To use existing ASP.Net Skins in an ASP.Net page we need to assign the existing theme at page level as in the following.

In the preceding source code, we are assigning the existing ASP.Net Skin File at page level, the existing ASP.Net Skin automatically appears in the box after using the Themes property in the page header.

Assigning the Skin to the ASP.Net Controls to assign the skin to the ASP.Net controls, you need to assign it to the control's SkinId Property as in the following:

The master pages can be used to accomplish the following:

Creating a set of controls that are common across all the web pages and attaching them to all the web pages.

§ A centralized way to change the above created set of controls which will effectively change all the web pages.

§ To some extent, a master page looks like a normal ASPX page.

§ It contains static HTML such as the <html>, <head>, and <body> elements, and it can also contain other HTML and ASP.NET server controls.

§ Inside the master page, you set up the markup that you want to repeat on every page, like the general structure of the page and the menu.

§ However, a master page is not a true ASPX page and cannot be requested in the browser directly it only serves as the template that real web pages called content pages

§ One difference is that while web forms start with the Page directive, a master page starts with a

Master directive that specifies the same information, as shown here

Windows-based authentication:

§ It causes the browser to display a login dialog box when the user attempts to access restricted page. § It is supported by most browsers.

§ It is configured through the IIS management console.

§ It uses windows user accounts and directory rights to grant access to restricted pages.

Forms-based authentication:

§ Developer codes a login form that gets the user name and password.

§ The username and password entered by user are encrypted if the login page uses a secure connection.

§ It doesn’t reply on windows user account.

To set an application to use forms authentication, follow these steps:

1. Click Select Authentication Type.

2. Choose the From the Internet option.

3. Click Done. The appropriate <authorization> tag will be created in the web.config file.

Next, it’s time to define the authorization rules. To do so, click the Create Access Rules link

§ UpdatePanel is a container control. A page can have multiple update panels.

§ The UpdatePanel control enables you to create a flicker free page by providing partial-page update support to it.

§ It identifies a set of server controls to be updated using an asynchronous post back.

§ If a control within the UpdatePanel causes a post back to the server, only the content within that UpdatePanel is refreshed.

<asp:UpdatePanel ID="UpdatePanel1" runat="server">

<ContentTemplate>

</ContentTemplate>

</asp:UpdatePanel

ScriptManager

§ The ScripManager Control manages the partial page updates for UpdatPanel controls that are on the ASP.NET web page or inside a user control on the web page.

§ This control manages the client script for AJAX-enabled ASP.NET web page and ScripManager control support the feature as partial-page rendering and web-service calls.

§ The ScriptManager control manages client script for AJAX-enabled ASP.NET Web pages.

§ Although this control is not visible at runtime, it is one of the most important controls for an Ajax enabled web page.

§ There can be only one ScriptManager in an Ajax enabled web page.

<asp:ScriptManager ID="ScriptManager1" runat="server" />