JanaDotNet

Wednesday 1 June 2016

Top 10 Features In ASP.NET 4.5

1 - Enable Trace feature
Answer

Trace is an ASP. NET feature that displays some useful information that you can't get by using Debugger. The ASP. NET Trace feature traces the execution of a page and displays trace information. In addition to this, it also displays other information at the bottom of that page.

To use the Trace feature, you must first enable tracing. To active the Trace feature for a page, you should add a Trace attribute to the page directive at the top of the aspx file for the page and set its value to true to this attribute as shown below.

When you run the page, trace information will be displayed at the end of the page as an output. When you enable the Trace feature, it is enabled only for the current page, which is usually what you require. To enable tracing for another page, you must modify the page directive. Once this feature has been enabled for a page, ASP.NET adds trace output to the page whenever the page is requested.

For more details, click on the link:

Enable Trace Feature in ASP.NET

2 - Strongly Typed Data Controls

Answer
The benefit of the Strongly Typed Data Controls feature is that we can bind the data to the display controls with strong types and we can avoid the exceptions caused by the function Eval(expression), if the expression is not evaluated to a proper value.

This article discusses with the help of the sample code about how the data binding was programmed before ASP.NET 4.5 and in ASP.NET 4.5. This example uses Visual Studio 2012 and the project type created is a simple web site project (empty web site project). Add a default.aspx webform with code at the back end, if you do not see it in the project.

Before ASP.NET 4.5

ASPX page:
We used Eval(expression) to bind the data to the individual controls in the List view control, which is shown below:

<p><u>Normal ASP.NET Binding</u></p>
<asp:ListView ID="displayData" runat="server">
<LayoutTemplate>
<table id="Table1" runat="server">
<tr id="Tr1" runat="server">
<td id="Td1" runat="server">
Item ID
</td>
<td id="Td2" runat="server">
Item Name
</td>
</tr>
<tr id="ItemPlaceholder" runat="server">
</tr>
</table>
</LayoutTemplate>
<ItemTemplate>
<tr>
<td>
<asp:Label ID="Label1" runat="server" Text='<%# Eval("ID")%>'>
</asp:Label>
</td>
<td>
<asp:Label ID="Label2" runat="server" Text='<%# Eval("ItemName")%>'>
</asp:Label>
</td>
</tr>
</ItemTemplate>
</asp:ListView>

Code behind populating the data:
Create a class file called "Product" in a separate file and it will be added in "App_code" folder in the project. This type will be used in the code running at the back end for populating the data of the type "Product".

/// <summary>
/// Summary description for Product
/// </summary>
public class Product
{
public int ID
{
get;
set;
}
public string ItemName
{
get;
set;
}
}
/// <summary>
/// Page Load Method
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
protected void Page_Load(object sender, EventArgs e)
{
//bind the data to the list view by calling the method PopulateProducts.
displayData.DataSource = PopulateProducts();
displayData.DataBind();
}
/// <summary>
/// Method to create new product
/// </summary>
/// <returns></returns>
public IList < Product > PopulateProducts()
{
return new List < Product >
{
new Product
{
ID = 1, ItemName = "Item1"
},
new Product
{
ID = 2, ItemName = "Item2"
},
new Product
{
ID = 3, ItemName = "Item3"
},
new Product
{
ID = 4, ItemName = "Item4"
}
};
}

Code Execution:
Your output will look as follows:

For more details, click on the link:

Strongly Typed Data Controls in ASP.Net

3 –Performance Tuning in ASP.Net

Answer
The following are the points which one needs to check before collecting data as a .NET developer.

Set debug=false in web.config

When you create the ASP.Net Web Application, by default this attribute is set to "true" in the web.config file that is very useful when developing. However, when you are deploying your Application, always set it to "false". Setting it to "true" requires the pdb information to be inserted into the file and that results in a comparatively larger file and hence processing will be slow. Hence, always setdebug="false" before deployment.

Turn off Tracing unless until required

Tracing enables us to track the Application's trace and the sequences that the developer needs to monitor the trace. When Trace is enabled, it tries to add extra information to the page. Always set this to "false", unless you require monitoring the trace logging in the production web.config.

<trace enabled="false" requestLimit=”10” pageoutput=”false” traceMode=”SortByTime” localOnly=”true”>

Choose Session State management carefully
One extremely powerful feature of ASP.NET is its ability to store session state for the users for any Web Applications. Since ASP.NET manages session state by default, we pay the cost in memory, even if you don't use it. In other words, whether you store your data in process or on a state Server or in a SQL Database, session state requires memory and it's also time consuming when you store or retrieve data from it. You may not require session state, when your pages are static or when you do not need to store information captured in the page. In such cases, where there is no need to use session state, disable it on your Web form using the directive:

<@%Page EnableSessionState="false"%>

For more details, click on the link:

Performance Tuning in ASP.Net Web Applications

4 - ASP.NET Web API
Answer
The ASP.NET Web API is one of the Microsoft open source technologies to build the powerful REST Services which will communicate across all the platforms and devices over HTTP.

Step 1: Create ASP.NET Web API Service.

After adding the MVC project, the Solution Explorer will look as shown below:

After creating the ASP.NET Web API project, the preceding folder structure and files are added into the project by default, which are the same as MVC project, so let us learn about them in brief as depicted below:

App_Start folder

This folder contains the Application configuration details such as routing, authentication, filtering of URL and so on.
Controller
This folder contains the Controller and their methods. The Controller is responsible for processing the user request and returns output as a view.
Models
This folder contains the entities or properties used to store the input values.

Step 2: Create Model Class.

EmpModel.cs

public class EmpModel
{
public string Name { get; set; }
public string City { get; set; }
}

Step 3: Add Web API Controller.

HomeController.cs

using System;
using System.Web.Http;
namespace CreatingWebAPIService.Controllers
{
public class HomeController: ApiController
{
[HttpPost]
public bool AddEmpDetails()
{
return true;
//write insert logic
}
[HttpGet]
public string GetEmpDetails()
{
return "Vithal Wadje";
}
[HttpDelete]
public string DeleteEmpDetails(string id)
{
return "Employee details deleted having Id " + id;
}
[HttpPut]
public string UpdateEmpDetails(string Name, String Id)
{
return "Employee details Updated with Name " + Name + " and Id " + Id;
}
}
}

The following is the default URL structure of ASP.NET Web API defined into the WebApiConfig.cs file.

Step 5: Testing Web API REST service using REST client.

Now let us test the application using REST client as:

POST:

In the image shown above Web API REST Service-HTTP POST method returns the 200 Status code which means REST service is successfully executed.

GET Method

In the image depicted above, Web API REST Service- HTTP GET method returns the 200 Status code which means REST service is successfully executed and returns the XML format output.

Note

The Web API REST service by default returns the output as per the browser default message header such as XML or JSON.

For more details, click on the link:

Creating ASP.NET Web API REST Service

5- Support for WebSockets protocol

Answer

Web Sockets

Create a single bi-directional connection between a Client & Server. It means that the client can send a request to the Server and forget, when the data is ready at the Server; where the Server will send it to the Client.
Native to the Browser, which makes them light weight and easy to implement.
Uses its own protocol and can tunnel thru Firewalls and Proxy with no extra effort. i.e Client does not use HTTP request but when a new WebSocket connection establishes, then the Browser establishes the HTTP connection with the Server and subsequently upgrades that connection to a dedicated WebSocket connection by setting a tunnel passing thru Firewall and Proxies.
Once the connection is established (as depicted above), it is a two way channel on which the Client and Server can communicate.

Creating a WebSocket is as easy as the code shown below:

var ws = new WebSocket("ws:<URL>");

Once the connection is established, there are the methods to control i terms off sending the data and monitoring the connection.

ws.onopen = function(){ } // Connection Open
ws.onmessage = function(){ } // received update
ws.onopen = function(){ } // Connection Close
//Funtions of WebSocket Object
ws.send(<text>);
ws.close();

Advantages:

Since the Firewall is bypassed, the streaming is very easy and can be done through any connection.
Does not need a separate connection for up-stream and down-stream.
Can be used with any client like AIR & Flex which comes with JavaScript support.

Limitations:

All Browsers do not support WebSockets as of now.

To see which Browser supports which feature of HTML5, you may refer to this link in wikipedia. It, however talks about the support in terms of a layout engine, which is an engine used to render the UI in the Browser. Though you can easily determine which Browser it uses; and which layout engine. Let me also provide it here for quick reference.

Browser	Layout Engine	Comments
Internet Explorer	Trident / MSHTML(DLL)	IE 8.0 = Trident4.0 = MSHTML DLL (8.0
Firefox	Gecko	http://en.wikipedia.org/wiki/Gecko_(layout_engine)
Chrome	Webkit	http://en.wikipedia.org/wiki/WebKit
Safari	webkit

For more details, click on link:

Websocket API in HTML 5

6 - Support for improved paging in ASP.NET 4.5 GridView control
Answer
When there are bulk records to show in the GridView, the developers often use paging to distribute the complete records with multiple pages to show the records in the GridView. This means that, when you change the page index, the GridView is bound everytime from the database to show the next records.

There are mainly two ways to implement paging in the GridView.

The first is, we can use Gridview's default paging by setting its property AllowPaging="true". The GridView will show the pager itself which depends on the PageSize and total records. This way is very tedious and degrades the performance of the Application because every time the PageIndex changes and the GridView will be bound with the complete data source that is not required at all, as we need to show only the data to the corresponding PageIndex.

To improve the performance of the web application, we usually create a custom paging control using many buttons or in any other way, since it binds the GridView with only relevant rows when the PageIndex changes. It was also very tedious to handle all the combinations of the clicks on the page links and write a lot of code-behind code in the .cs file.

Code of ASPX page.
The following mark to set GridView control.

For more details, click on the link:

Custom Paging With GridView in ASP.NET 4.5

7 - Enhanced support for asynchronous programming

Answer
In the current .NET Framework (4.5.1) and Windows Runtime, asynchronous programming has the power of the asynchronous support. The compiler performs the difficult work that the developer used to do and your Application retains a logical structure that resembles synchronous code. By using all of this, you can get the advantage of asynchronous programming.

What is Synchronous?

Synchronous represents a set of activities that starts happening together at the same time.
A synchronous call waits for the method to complete before continuing with the program flow.

In general, asynchronous programming makes sense in two cases as:

If you are creating a UI intensive application in which the user experience is the prime concern. In this case, an asynchronous call allows the user interface to remain responsive. Unlike as shown in Figure 1-1.
If you have other complex or expensive computational work to do, you can continue; interact with the application UI while waiting for the response back from the long-running task.

Asynchronous Programming Model Pattern

Relies on two corresponding methods to represent an asynchronous operation: BeginMethodName and EndMethodName.
Most often you must have seen this; while using delegates or method invocation from a Web Service.

For more details, click on the link:

Asynchronous Programming With C# 5.0

8 - Garbage Collector Improvements
Answer
A look through what MSDN has to say,

"The .NET Framework's garbage collector manages the allocation and release of memory for your application. The garbage collector's optimizing engine determines the best time to perform a collection, based upon the allocations being made. When the garbage collector performs a collection, it checks for objects in the managed heap that are no longer being used by the application and performs the necessary operations to reclaim their memory."

Each of us has heard about managed and unmanaged code. What is a managed code? OOPS basics, this is related to automatic memory management by Garbage Collection, so called GC.

GC in .NET is a very heavy process; this is improved in .NET 4.5. These improvements are intended to provide value for the developers who build large-scale Client and Server apps and many smaller apps, as well.

Garbage Collection till .NET 4.0

GC had many challenges in the older versions of .NET. The larger the application is, the more resources it will consume. ASP.NET applications run on the Server and a lot of Clients send requests to the Server which creates loads of objects, making the GC really work hard for cleaning up unwanted objects. This caused larger pause for the Application as it lowers the efficiency and the large object heap takes up more space.

To be clear, till the earlier version of .NET, i.e. .NET 4.0, when there are different threads doing their work and have managed code as well, at some point of time the GC runs creating a pause in the Application suspending all the application threads, making the Server less responsive.

What’s new in .NET 4.5 GC?
.NET 4.5 has overcome this problem, by introducing Server GC. This creates one more thread in the background, which cleans the objects. This handles only Gen 2 objects, reduces the load on main GC thread. The two threads running simultaneously reduces the suspension time and improves the Application throughput.

Enabling GC server

The GC server can be enabled by using GCServer XML tag in the web.config and enable it to true.

<configuration>
<runtime>
<gcServer enabled="true"/>
</runtime>
</configuration>

For more details, click on the link:

Garbage Collection In .NET 4.5

9 - Support for HTML5 form types
Answer
ASP.NET 4.5 provides excellent support for HTML5 form types. In HTML5, several new input types have been added and these new input types are: Sliders, Number Spinners, Popup Calendars, Color Choosers, Autocompleting suggestion boxes and more.

This article covers the new input types:

Color
Date
Datetime
Email
Month
Number
Range
Search
Tel
Time
URL
Week

In order to define, all these new input types the "<input>" Tag is used.

Input type Color

Description
This input type allows the collection of a color of the form. If a Browser supports this input type then the
intention is that clicking in the textfield will result in a Color Chooser that pops up.

The input element with a type attribute, whose value is "color" represents a color-well control to set the element's value to a string representing a simple color.

Note: Color keywords (for example, strings such as "red" or "green") are not allowed.

Syntax
<input type="color" name="some-name"/>

Example of color input type
1. <!DOCTYPE html>
3. <html lang="en" xmlns="http://www.w3.org/1999/xhtml">
5. <head>
6. <meta charset="utf-8" />
7. <title>Color</title>
8. </head>
10. <body>
11. <h2>Implementation Of color as New Input Type</h2>
12. <form action="form.asp">
13. Choose your favorite color:
14. <input type="color" name="favcolor"><br>
15. <br>
16. <input type="submit">
17. </form>
18. </body>
20. </html>
Input type Date

Description
The date type allows the user to select a date. The input element with a type attribute whose value is "date" represents a control for setting the element's value to a string, representing a date. In simple words, we can say that this input type allows collection of a date.

Syntax
<input type="date" name="some-name"/>
Input type DateTime

Description
The datetime type allows the user to choose a date and time (with time zone).The input element with a type attribute, whose value is "datetime" represents a control to set the element's value to a string representing a global date and time (with timezone information).

Syntax
<input type="datetime" name="some-name"/>
Input type Email

Description

The Email type is used for input fields that should contain an e-mail address. This gives liberty to have a field to fill E-mail address(es). This input type allows collection of an Email address. If the "list" attribute is not specified, then the intention is that the Browser supplies some help in entering a legal email address (e.g., the iPhone Browser uses an Email-optimized keyboard) and/or validation on submission.

Syntax
<input type="email" name="some-name"/>
<input type="email" list="email-choices" name="some-name"/>
<datalist id="email-choices">
<option label="First Person" value="abc@example.com">
<option label="Second Person" value="xyz@example.com">
<option label="Third Person" value="pqr@example.com">
...
</datalist>
Input type number

Description
The number type is for the input fields that should contain a numeric value. This input type allows a collection of a number (either integer or floating point). In other words, input type number means picking a number.
The input element with a type attribute, whose value is "number" represents a precise control for setting the element's value to a string representing a number.

Syntax
<input type="number" min="0" max="20" step="2" value="10" name="some-name"/>
Input type month
Description
The month type allows the user to choose a full month and an year.

The input element with a type attribute, whose value is "month" represents a control to set the element's value to a string representing a month.

Syntax
<input type="month" name="some-name"/>
Input type range
Description
This input type allows a collection of a number (either integer or floating point). All known Browsers that support this use a Slider. The exact value is not displayed to the user unless you use JavaScript.

Hence, use the number (Spinner) input type if you want to let the user choose an exact value. Browsers are supposed to use a Horizontal Slider unless you attach CSS, that specifies a smaller width than height, in which case, they are supposed to use a Vertical Slider that sets to a certain value/position.

Syntax
<input type="range" name="some-name"/>
Input type tel
Description

It is used to enter a telephone number.

This input type is intended to help you collect a telephone number. Since the format of telephone numbers is not specified, it is not clear how a normal Browser would help you with this. However, a cell phone might use an on-screen keyboard that is optimized for phone number input.

Syntax
<input type="tel" name="some-name"/>
Input type time
Description
It allows the user to select a time. The input element with a type attribute, whose value is "time" represents a control to set the element's value to a string representing a time (with no timezone information).

Syntax

<input type="time" name="some-name"/>
Input type week
Description

The week type allows the user to select a week and an year. In other words, it means picking up a specific week.

Syntax
<input type="week" name="some-name"/>
Input type Search

Description

This input type is intended to help you collect a string for a search. Since search queries are free-form text, there is never any help in inputting characters and you never have any validation on submission. However, on some platforms, search fields should look slightly different than regular textfields (e.g., with rounded corners instead of with square corners).

Define a search field (like a site search, or Google search).

Syntax

<input type="search" name="some-name"/>
Input type URL
Description

This input type allows a collection of an absolute URL. If the "list" attribute is not specified, then the intention is that the Browser supplies some help in entering a legal URL (e.g., the iPhone browser uses a URL-optimized keyboard) and/or validation on the submission.

If the "list" attribute is specified, then the intention is that the Browser allows the user to choose among a set of URLs defined separately with the "datalist" element.

Syntax
<input type="url" name="some-name"/>
<input type="url" list="url-choices" name="some-name"/>
<datalist id="url-choices">
<option label="HTML5 Spec" value="http://dev.w3.org/html5/spec/">
<option label="Some other URL" value="http://example.com/blah.html">
<option label="Yet Another URL" value="http://foo.bar.com/baz.html">
...
</datalist>

For more details, click on the link:

HTML5 New Input Types

10 - Bundling and Minification in ASP.NET

Answer

Bundling: In ASP.NET, bundling is a process of wrapping up all included files as a single downloadable resource so that the Browser's call for resources is minimized. Instead of making a one-for-one call for each file, the Browser gets all bundled files in a single call.

Minification: Minification is the process of the removal of all unnecessary characters like extra spaces, comments, new lines and so on, that has been added for readability, from the files to reduce the size of the files so that the data transfer can be minimized.

Let us understand it by an example. Suppose, we have a function for sum:

function sum(a,b)
{
return (a + b); //will return the sum of numbers
}

Generally, when we write this function in a file, the entire JavaScript file is downloaded as it is. With a minified JavaScript file, the code shown above will look like:

function sum(a,b){return (a+b);}

Clearly, it reduces the size of the file.

When to apply bundling

Having many common JavaScript/CSS files used throughout the Application
Too many JavaScript/CSS files in use in a page

For more details, click on the link:

Object Oriented Programming Using C# .NET

Chapter Objective

OOP's overview
Classes and Objects
Constructor and Destructor
Function Overloading
Encapsulation
Inheritance
Interface
Polymorphism

OOP's overview

Object-oriented programming (OOP) is the core ingredient of the .NET framework. OOP is so important that, before embarking on the road to .NET, you must understand its basic principles and terminology to write even a simple program. The fundamental idea behind OOP is to combine into a single unit both data and the methods that operate on that data; such units are called an object. All OOP languages provide mechanisms that help you implement the object-oriented model. They are encapsulation, inheritance, polymorphism and reusability. Let's now take a brief look at these concepts.

Encapsulation
Encapsulation binds together code and the data it manipulates and keeps them both safe from outside interference and misuse. Encapsulation is a protective container that prevents code and data from being accessed by other code defined outside the container.

Inheritance

Inheritance is the process by which one object acquires the properties of another object. A type derives from a base type, taking all the base type members fields and functions. Inheritance is most useful when you need to add functionality to an existing type. For example all .NET classes inherit from the System.Object class, so a class can include new functionality as well as use the existing object's class functions and properties as well.

Polymorphism
Polymorphism is a feature that allows one interface to be used for a general class of action. This concept is often expressed as "one interface, multiple actions". The specific action is determined by the exact nature of circumstances.

Reusability
Once a class has been written, created and debugged, it can be distributed to other programmers for use in their own program. This is called reusability, or in .NET terminology this concept is called a component or a DLL. In OOP, however, inheritance provides an important extension to the idea of reusability. A programmer can use an existing class and without modifying it, add additional features to it.

Simple "Hello World" C# Program

This simple one-class console "Hello world" program demonstrates many fundamental concepts throughout this article and several future articles.

C# code

using System;
namespace oops
{
//class definition
public class SimpleHelloWorld
{
//Entry point of the program
static void Main(string[] args)
{
//print Hello world"
Console.WriteLine("Hello World!");
}
}
}

So SimpleHelloWorld is the name of the class that contains the Main () method. On line 1 , a using directive indicates to the compiler that this source file refers to classes and constructs declared within the System namespace. Line 6 with the public keyword indicates the program accessibility scope for other applications or components.

At line 7 there appears an opening curly brace ("{") which indicates the beginning of the SimpleHelloWorld class body. Everything belongs to the class, like fields, properties and methods appear in the class body between the opening and closing braces. The purpose of the Main () method is to provide an entry point for application execution.

The static keyword in the Main () method states that this method would be executed without instantiating the class.

Compiling the Program

You can compile a C# program into either an assembly or a module. If the program has one class that contains a Main () method then it can be compiled directly into an assembly. This file has an ".exe" extension. A program with no Main() method can be compiled into a module as in the following:

csc /target:module "program name"

You can then compile this program by F9 or by simply running the C# command line compiler (csc.exe) against the source file as the following:

csc oops.cs

Classes and Objects

Classes are special kinds of templates from which you can create objects. Each object contains data and methods to manipulate and access that data. The class defines the data and the functionality that each object of that class can contain.

A class declaration consists of a class header and body. The class header includes attributes, modifiers, and the class keyword. The class body encapsulates the members of the class, that are the data members and member functions. The syntax of a class declaration is as follows:

Attributes accessibility modifiers class identifier: baselist { body }

Attributes provide additional context to a class, like adjectives; for example the Serializable attribute. Accessibility is the visibility of the class. The default accessibility of a class is internal. Private is the default accessibility of class members. The following table lists the accessibility keywords;

Keyword	Description
public	Public class is visible in the current and referencing assembly.
private	Visible inside current class.
protected	Visible inside current and derived class.
Internal	Visible inside containing assembly.
Internal protected	Visible inside containing assembly and descendent of thecurrent class.

Modifiers refine the declaration of a class. The list of all modifiers defined in the table are as follows;

Modifier	Description
sealed	Class can't be inherited by a derived class.
static	Class contains only static members.
unsafe	The class that has some unsafe construct likes pointers.
Abstract	The instance of the class is not created if the Class is abstract.

The baselist is the inherited class. By default, classes inherit from the System.Object type. A class can inherit and implement multiple interfaces but doesn't support multiple inheritances.

Step-by-step Tutorial for Creating a Class

Open Visual Studio 2010 from start menu.
Go to "File" > "New" > "Project...", select "Console Application" in the right pane and provide the name "oops" for the project.
Then in the Solution Explorer, you will notice some files that are automatically created as:
You can also write your own code in the default program.cs file that is created but it is a good programming practice to create a new class.
For adding a new class, right-click over the project name (oops) in the Solution Explorer, then click "Add" > "Class". Give the name to the class "customer" as in the following;
When you open the customer.cs class. you will find some default-generated code as in the following;

C# code

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace oops
{
class customer
{
}
}

Note: the C# console application project must require a single entry point Main () function that is already generated in the program class. For example if you add a new customer class and want to define one or more Main () entry points here then .NET will throw an error of multiple entry points. So it is advisable to delete or exclude the program.cs file from the solution.

So here in this example the customer class defines fields such as CustID, Name and Address to hold information about a particular customer. It might also define some functionality that acts upon the data stored in these fields.

C# code

using System;
namespace oops
{
class customer
{
// Member Variables
public int CustID;
public string Name;
public string Address;
//constuctor for initializing fields
customer()
{
CustID=1101;
Name="Tom";
Address="USA";
}
//method for displaying customer records (functionality)
public void displayData()
{
Console.WriteLine("Customer="+CustID);
Console.WriteLine("Name="+Name);
Console.WriteLine("Address="+Address);
}
// Code for entry point
}
}

At line 9, we are defining a constructor of the customer class for initializing the class member fields. The constructor is a special function that is automatically called when the customer class object is created (instantiated). And at line 11 we are printing these fields to the console by creating a user defined method displayData(). You can then instantiate an object of this class to represent one specific customer, set the field value for that instance and use its functionality, as in:

C# code

class customer
{
// class members code
//Entry point
static void Main(string[] args)
{
// object instantiation
customer obj = new customer();
//Method calling
obj.displayData();
//fields calling
Console.WriteLine(obj.CustID);
Console.WriteLine(obj.Name);
Console.WriteLine(obj.Address);
}
}

Here you use the keyword new to declare the customer class instance. This keyword creates the object and initializes it. When you create an object of the customer class, the .NET framework IDE provides a special feature called Intellisense that provides access to all the class member fields and functions automatically. This feature is invoke when the "." Operator is put right after the object, as in the following;

Image 3.jpg

Image 1.1 Intellisense feature

Normally, as the program grows in size and the code becomes more complex, the Intellisense feature increases the convenience for the programmer by showing all member fields, properties and functions.

Multiple Class Declaration

Sometimes circumstances require multiple classes to be declared in a single namespace. So in that case it is not mandatory to add a separate class to the solution, instead you can attach the new class into the existing program.cs or another one as in the following;

C# code

using System;
namespace oops
{
class Program
{
public void MainFunction()
{
Console.WriteLine("Main class");
}
static void Main(string[] args)
{
//main class instance
Program obj = new Program();
obj.MainFunction();
//other class instace
demo dObj=new demo();
dObj.addition();
}
}
class demo
{
int x = 10;
int y = 20;
int z;
public void addition()
{
z = x + y;
Console.WriteLine("other class in Namespace");
Console.WriteLine(z);
}
}
}

Here in this example, we are creating an extra class "demo" in the program.cs file at line 12 and finally we are instantiating the demo class with the program class inside the Main() entry in lines 6 to 11. So it doesn't matter how many classes we are defining in a single assembly.

Partial classes

Typically, a class will reside entirely in a single file. However, in situations where multiple developers need access to the same class, then having the class in multiple files can be beneficial. The partial keywords allow a class to span multiple source files. When compiled, the elements of the partial types are combined into a single assembly.

There are some rules for defining a partial class as in the following;

A partial type must have the same accessibility.
Each partial type is preceded with the "partial" keyword.
If the partial type is sealed or abstract then the entire class will be sealed and abstract.

In the following example we are adding two files, partialPart1.cs and partialPart2.cs, and declare a partial class, partialclassDemo, in both classes.

partialPart1.cs

using System;
namespace oops
{
public partial class partialclassDemo
{
public void method1()
{
Console.WriteLine("method from part1 class");
}
}
}

partialPart2.cs

using System;
namespace oops
{
public partial class partialclassDemo
{
public void method2()
{
Console.WriteLine("method from part2 class");
}
}
}

And finally we are creating an instance of the partialclassDemo in the program.cs file as the following:

Program.cs

using System;
namespace oops
{
class Program
{
static void Main(string[] args)
{
//partial class instance
partialclassDemo obj = new partialclassDemo();
obj.method1();
obj.method2();
}
}
}

Static classes

A static class is declared using the "static" keyword. If the class is declared as static then the compiler never creates an instance of the class. All the member fields, properties and functions must be declared as static and they are accessed by the class name directly not by a class instance object.

C# code

using System;
namespace oops
{
static class staticDemo
{
//static fields
static int x = 10, y;
//static method
static void calcute()
{
y = x * x;
Console.WriteLine(y);
}
static void Main(string[] args)
{
//function calling directly
staticDemo.calcute();
}
}
}

Creating and accessing Class Component Library

.NET provides the capability of creating libraries (components) of a base application rather than an executable (".exe"). Instead the library project's final build version will be ".DLL" that can be referenced from other outside applications to expose its entire functionality.

Step-by-step tutorial

1. First create a class library based application as:

Image 4.jpg

2. Then we are implementing a math class library that is responsible of calculating square root and the addition of two numbers as:

using System;
namespace LibraryUtil
{
public class MathLib
{
public MathLib() { }
public void calculareSum(int x, int y)
{
int z = x + y;
Console.WriteLine(z);
}
public void calculareSqrt(double x)
{
double z = Math.Sqrt(x);
Console.WriteLine(z);
}
}
}

3. Build this code and you will notice that a DLL file was created, not an executable, in the root directory of the application (path = D:\temp\LibraryUtil\LibraryUtil\bin\Debug\ LibraryUtil.dll).

4. Now create another console based application where you utilize all the class library's functionality.

5. Then you have to add the class library dll file reference to access the declared class in the library dll. (Right-click on the Reference then "Add reference" then select the path of the dll file.)

6. When you add the class library reference then you will notice in the Solution Explorer that a new LibraryUtil is added as in the following;

Image 5.jpg

7. Now add the namespace of the class library file in the console application and create the instance of the class declared in the library as in the following;

using System;
using LibraryUtil; // add library namespace
namespace oops
{
public class LibraryClass
{
static void Main()
{
//library class instance
MathLib obj = new MathLib();
//method populate
obj.calculareSum(2, 5);
obj.calculareSqrt(25);
}
}
}

8. Finally run the application.

Constructor and Destructor

A constructor is a specialized function that is used to initialize fields. A constructor has the same name as the class. Instance constructors are invoked with the new operator and can't be called in the same manner as other member functions. There are some important rules pertaining to constructors as in the following;

Classes with no constructor have an implicit constructor called the default constructor, that is parameterless. The default constructor assigns default values to fields.
A public constructor allows an object to be created in the current assembly or referencing assembly.
Only the extern modifier is permitted on the constructor.
A constructor returns void but does not have an explicitly declared return type.
A constructor can have zero or more parameters.
Classes can have multiple constructors in the form of default, parameter or both.

The following example shows one constructor for a customer class.

C# code

using System;
namespace oops
{
class customer
{
// Member Variables
public string Name;
//constuctor for initializing fields
public customer(string fname, string lname)
{
Name= fname +" "+ lname;
}
//method for displaying customer records
public void AppendData()
{
Console.WriteLine(Name);
}
//Entry point
static void Main(string[] args)
{
// object instantiation
customer obj = new customer("Barack", "Obama");
//Method calling
obj.AppendData();
}
}
}

Note: The moment a new statement is executed, the default constructor is called.

Static Constructor

A constructor can be static. You create a static constructor to initialize static fields. Static constructors are not called explicitly with the new statement. They are called when the class is first referenced. There are some limitations of the static constructor as in the following;

Static constructors are parameterless.
Static constructors can't be overloaded.
There is no accessibility specified for Static constructors.

In the following example the customer class has a static constructor that initializes the static field and this constructor is called when the class is referenced in the Main () at line 26 as in the following:

C# code

using System;
namespace oops
{
class customer
{
// Member Variables
static private int x;
//constuctor for static initializing fields
static customer()
{
x = 10;
}
//method for get static field
static public void getData()
{
Console.WriteLine(x);
}
//Entry point
static void Main(string[] args)
{
//static Method calling
customer.getData();
}
}
}

Destructors

The purpose of the destructor method is to remove unused objects and resources. Destructors are not called directly in the source code but during garbage collection. Garbage collection is nondeterministic. A destructor is invoked at an undetermined moment. More precisely a programmer can't control its execution; rather it is called by the Finalize () method. Like a constructor, the destructor has the same name as the class except a destructor is prefixed with a tilde (~). There are some limitations of destructors as in the following;

Destructors are parameterless.
A Destructor can't be overloaded.
Destructors are not inherited.
Destructors can cause performance and efficiency implications.

The following implements a destructor and dispose method. First of all we are initializing the fields via constructor, doing some calculations on that data and displaying it to the console. But at line 9 we are implementing the destructor that is calling a Dispose() method to release all the resources.

using System;
namespace oops
{
class customer
{
// Member Variables
public int x, y;
//constuctor for initializing fields
customer()
{
Console.WriteLine("Fields inititalized");
x = 10;
}
//method for get field
public void getData()
{
y = x * x;
Console.WriteLine(y);
}
//method to release resource explicitly
public void Dispose()
{
Console.WriteLine("Fields cleaned");
x = 0;
y = 0;
}
//destructor
~customer()
{
Dispose();
}
//Entry point
static void Main(string[] args)
{
//instance created
customer obj = new customer();
obj.getData();
}
}
}

At line 12 when the instance is created, fields are initialized but it is not necessary that at the same time the destructor is also called. Its calling is dependent on garbage collection. If you want to see the destructor being called into action then put a breakpoint (by F9) at line 10 and compile the application. The CLR indicates its execution at the end of the program by highlighting line 10 using the yellow color.

Function Overloading

Function overloading allows multiple implementations of the same function in a class. Overloaded methods share the same name but have a unique signature. The number of parameters, types of parameters or both must be different. A function can't be overloaded on the basis of a different return type alone.

using System;
namespace oops
{
class funOverload
{
public string name;
//overloaded functions
public void setName(string last)
{
name = last;
}
public void setName(string first, string last)
{
name = first + "" + last;
}
public void setName(string first, string middle, string last)
{
name = first + "" + middle + "" + last;
}
//Entry point
static void Main(string[] args)
{
funOverload obj = new funOverload();
obj.setName("barack");
obj.setName("barack "," obama ");
obj.setName("barack ","hussian","obama");
}
}
}

At lines 3, 4 and 5 we are defining three methods with the same name but with different parameters. In the Main (), the moment you create an instance of the class and call the functions setName() via obj at lines 7, 8 and 9 then intellisense will show three signatures automatically.

Encapsulation

Encapsulation is the mechanism that binds together the code and the data it manipulates, and keeps both safe from outside interference and misuse. In OOP, code and data may be combined in such a way that a self-contained box is created. When code and data are linked together in this way, an object is created and encapsulation exists.

Within an object, code, data or both may be private or public to that object. Private code is known to and accessible only by another part of the object, that is private code or data may not be accessible by a piece of the program that exists outside the object. When the code and data is public, other portions of your program may access it even though it is defined within an object.

C# code

using System;
namespace oops
{
class Encapsulation
{
/// <summary>
/// Every member Variable and Function of the class are bind
/// with the Encapsulation class object only and safe with
/// the outside inference
/// </summary>
// Encapsulation Begin
int x;
//class constructor
public Encapsulation(int iX)
{
this.x = iX;
}
//calculating the square
public void MySquare()
{
int Calc = x * x;
Console.WriteLine(Calc);
}
// End of Encapsulation
//Entry point
static void Main(string[] args)
{
//instance created
customer obj = new customer(20);
obj. MySquare();
}
}
}

Inheritance
Inheritance is the process by which one object can acquire the properties of another object. Inheritance is a "is a kind of" relationship and it supports the concept of classification in which an object needs only define those qualities that make it unique within the class. Inheritance involves a base class and a derived class. The derived class inherits from the base class and also can override inherited members as well as add new members to extend the base class.

A base type represents the generalization, whereas a derived type represents a specification of an instance. Such as Employees that can have diverse types, such as hourly, salaried and temporary so in that case Employees is the general base class and hourly, salaried and temporary employee are specialized derived classes.

Classes can inherit from a single class and one or more interfaces. When inheriting from a class, the derived class inherits the members including the code of the base class. The important point to remember is that Constructors and Destructors are not inherited from the base class.

The syntax of inheritance is as in the following;

Class derivedClass : baseClass, Iterface1, Interface2 { body }

For example we are defining two classes, Father and Child. You notice at line 7, we are implementing inheritance by using a colon (:); at this moment all the properties belonging to the Father Class is accessible to the Child class automatically.

Image 6.jpg

C# code

using System;
namespace oops
{
//Base Class
public class Father
{
public void FatherMethod()
{
Console.WriteLine("this property belong to Father");
}
}
//Derived class
public class Child : Father
{
public void ChildMethod()
{
Console.WriteLine("this property belong to Child");
}
}
class Inheritance
{
//Entry point
static void Main(string[] args)
{
Father fObj = new Father();
fObj.FatherMethod();
//Here Child object can access both class methods
Child cObj = new Child();
cObj.FatherMethod();
cObj.ChildMethod();
}
}
}

At line 11 , the Intellisense only shows the Father class functions but at line 15 to 16 the Child class object is able to access both class methods as in the following.

We can create a class in the VB.Net language or another .NET supported language and can inherit them in a C# .Net class and vice versa. But a class developed in C++ or other unmanaged environment can't be inherited in .NET.
Note: Cross-language and multiple inheritance is not supported by .NET.

Accessibility

Accessibility sets the visibility of the member to outside assemblies or derived types. The following table describes member accessibility;

Modifiers	Outside Assembly	Derived Class
private	No	No
public	Yes	Yes
protected	No	No
internal	Yes ( this assembly only)	Yes ( this assembly only)
internal protected	Yes ( this assembly only)	Yes

Constructor in Inheritance

Constructors in a base class are not inherited in a derived class. A derived class has a base portion and derived portion. The base portion initializes the base portion, and the constructor of the derived class initializes the derived portion.
The following is the syntax of a constructor in inheritance;

Accessibility modifier classname(parameterlist1) : base(parameterlist2) { body }

So the base keyword refers to the base class constructor, while parameterlist2 determines which overloaded base class constructor is called.

In the following example, the Child class's constructor calls the single-argument constructor of the base Father class;

C# code

using System;
namespace oops
{
//Base Class
public class Father
{
//constructor
public Father()
{
Console.WriteLine("Father class constructor");
}
public void FatherMethod()
{
Console.WriteLine("this property belong to Father");
}
}
//Derived class
public class Child : Father
{
public Child()
: base()
{
Console.WriteLine("child class constructor");
}
public void ChildMethod()
{
Console.WriteLine("this property belong to Child");
}
}
class Inheritance
{
//Entry point
static void Main(string[] args)
{
//Here Child object can access both class methods
Child cObj = new Child();
cObj.FatherMethod();
cObj.ChildMethod();
Console.ReadKey();
}
}
}

At line 4, we are defining a base Father Class constructor and in the derived class Child, at line 8 we are initializing it explicitly via base keyword. If we pass any parameter in the base class constructor then we have to provide them in the base block of the child class constructor.

Virtual Methods

By declaring a base class function as virtual, you allow the function to be overridden in any derived class. The idea behind a virtual function is to redefine the implementation of the base class method in the derived class as required. If a method is virtual in the base class then we have to provide the override keyword in the derived class. Neither member fields nor static functions can be declared as virtual.

C# code

using System;
namespace oops
{
class myBase
{
//virtual function
public virtual void VirtualMethod()
{
Console.WriteLine("virtual method defined in the base class");
}
}
class myDerived : myBase
{
// redifing the implementation of base class method
public override void VirtualMethod()
{
Console.WriteLine("virtual method defined in the Derive class");
}
}
class virtualClass
{
static void Main(string[] args)
{
// class instance
new myDerived().VirtualMethod();
Console.ReadKey();
}
}
}

Hiding Methods

If a method with the same signature is declared in both base and derived classes, but the methods are not declared as virtual and overriden respectively, then the derived class version is said to hide the base class version. In most cases, you would want to override methods rather than hide them. Otherwise .NET automatically generates a warning.

In the following example, we are defining a VirutalMethod() in the myBase class but not overriding it in the derived class, so in that case the compiler will generate a warning. The compiler will assume that you are hiding the base class method. So to overcome that problem, if you prefix the new keyword in the derived class method then the compiler will prefer the most derived version method. You can still access the base class method in the derived class by using the base keyword.

C# code

using System;
namespace oops
{
class myBase
{
//virtual function
public virtual void VirtualMethod()
{
Console.WriteLine("virtual method defined in the base class");
}
}
class myDerived : myBase
{
// hiding the implementation of base class method
public new void VirtualMethod()
{
Console.WriteLine("virtual method defined in the Derive class");
//still access the base class method
base.VirtualMethod();
}
}
class virtualClass
{
static void Main(string[] args)
{
// class instance
new myDerived().VirtualMethod();
Console.ReadKey();
}
}
}

Abstract Classes

C# allows both classes and functions to be declared abstract using the abstract keyword. You can't create an instance of an abstract class. An abstract member has a signature but no function body and they must be overridden in any non-abstract derived class. Abstract classes exist primarily for inheritance. Member functions, properties and indexers can be abstract. A class with one or more abstract members must be abstract as well. Static members can't be abstract.

In this example, we are declaring an abstract class Employess with a method displayData() that does not have an implementation. Then we are implementing the displayData() body in the derived class. One point to be noted here is that we have to prefixe the abstract method with the override keyword in the derived class.

C# code

using System;
namespace oops
{
//abstract class
public abstract class Employess
{
//abstract method with no implementation
public abstract void displayData();
}
//derived class
public class test : Employess
{
//abstract class method implementation
public override void displayData()
{
Console.WriteLine("Abstract class method");
}
}
class abstractClass
{
static void Main(string[] args)
{
// class instance
new test().displayData();
}
}
}

Sealed Classes

Sealed classes are the reverse of abstract classes. While abstract classes are inherited and are refined in the derived class, sealed classes cannot be inherited. You can create an instance of a sealed class. A sealed class is used to prevent further refinement through inheritance.

Suppose you are a developer of a class library and some of the classes in the class library are extensible but other classes are not extensible so in that case those classes are marked as sealed.

C# code

using System;
namespace oops
{
sealed class SealedClass
{
void myfunv();
}
public class test : SealedClass //wrong. will give compilation error
{
}
}

Interface
An interface is a set of related functions that must be implemented in a derived class. Members of an interface are implicitly public and abstract. Interfaces are similar to abstract classes. First, both types must be inherited; second, you cannot create an instance of either. Although there are several differences as in the following;

An Abstract class can contain some implementations but an interface can't.
An Interface can only inherit other interfaces but abstract classes can inherit from other classes and interfaces.
An Abstract class can contain constructors and destructors but an interface can't.
An Abstract class contains fields but interfaces don't.

So the question is, which of these to choose? Select interfaces because with an interface, the derived type still can inherit from another type and interfaces are more straightforward than abstract classes.

C# code

using System;
namespace oops
{
// interface
public interface xyz
{
void methodA();
void methodB();
}
// interface method implementation
class test : xyz
{
public void methodA()
{
Console.WriteLine("methodA");
}
public void methodB()
{
Console.WriteLine("methodB");
}
}
class interfaceDemo
{
static void Main(string[] args)
{
test obj = new test();
obj.methodA();
obj.methodB();
}
}
}

An interface can be inherited from other interfaces as in the following:

C# code

public interface xyz
{
void methodA();
void methodB();
}
public interface abc : xyz
{
void methodC();
}

Polymorphism
Polymorphism is the ability to treat the various objects in the same manner. It is one of the significant benefits of inheritance. We can decide the correct call at runtime based on the derived type of the base reference. This is called late binding.

In the following example, instead of having a separate routine for the hrDepart, itDepart and financeDepart classes, we can write a generic algorithm that uses the base type functions. The method LeaderName() declared in the base abstract class is redefined as per our needs in 2 different classes.

C# code

using System;
namespace oops
{
public abstract class Employee
{
public virtual void LeaderName()
{
}
}
public class hrDepart : Employee
{
public override void LeaderName()
{
Console.WriteLine("Mr. jone");
}
}
public class itDepart : Employee
{
public override void LeaderName()
{
Console.WriteLine("Mr. Tom");
}
}
public class financeDepart : Employee
{
public override void LeaderName()
{
Console.WriteLine("Mr. Linus");
}
}
class PolymorphismDemo
{
static void Main(string[] args)
{
hrDepart obj1 = new hrDepart();
itDepart obj2 = new itDepart();
financeDepart obj3 = new financeDepart();
obj1.LeaderName();
obj2.LeaderName();
obj3.LeaderName();
Console.ReadKey();
}
}
}

Article Extensions

OVERIDING EXAMPLE

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

namespace overriding

{

abstract class BaseClass

{

public abstract string YourCity();

}

class DerivedClass : BaseClass

{

public override string YourCity() //It is mandatory to implement absract method

{

return "London";

}

private int sum(int a, int b)

{

return a + b;

}

class Program

{

static void Main(string[] args)

{

DerivedClass obj = new DerivedClass();

string city = obj.YourCity();

Console.WriteLine(city);

Console.Read();

}