Difference Between Static Class, Sealed Class, and Abstract Class in C#

We come across this question very often that what is the difference between Static, Sealed and Abstract class in C#.


Static Class: Declared with Static keyword, methods in Static Class are also static along with variables of the class.

This class cannot be instantiated, i.e we cannot have objects of this class. To access methods of this class, you can directly use classname.method. Also this class cannot be inherited.



Sealed Class: Declared with Sealed keyword, which enables this class to seal all its variables, methods and properties. No other class can inherit anything from this class or in other words, this class cannot be inherited. But we can instantiate this class, i.e we can have any number of objects of a sealed class.



Abstract Class: Declared with abstract keyword, this class is primarily created as a Inheritable class. An abstract class enables other classes to inherit from this class, but forbids to instantiate. One can inherit from an abstract class but we cannot create objects of an abstract class. Abstract class can have abstract as well as non abstract methods. Abstract methods are those which are not having method definition.



One important point to remember is a non-static class can have static methods. But Static classes must have all members as Static.

Facebook Embedded Post (Responsive) in your website

<div id="fb-root"></div>

<script>(function(d, s, id) {
  var js, fjs = d.getElementsByTagName(s)[0];
  if (d.getElementById(id)) return;
  js = d.createElement(s); js.id = id;
  js.src = "//connect.facebook.net/en_US/all.js#xfbml=1";
  fjs.parentNode.insertBefore(js, fjs);
}(document, 'script', 'facebook-jssdk'));

</script>

<div id="post">
    <div class="fb-post" data-href="@ConfigClass.FacebookEmbedPost()" data-width="425"></div>
</div>

<script type="text/javascript">
(function($) {
jQuery.fn.autoResizeFbPost = function() {
var fixWidth = function($container, $clonedContainer, doParse) {        
// default parameter.
doParse = typeof doParse == 'undefined' ? true : doParse;
var updatedWidth = $container.width();
// update all div.fb-post with correct width of container
$clonedContainer
.find('div.fb-post')
.each(function() {
$(this).attr('data-width', updatedWidth);
});
// update page with adjusted markup
$container.html( $clonedContainer.html() );
// should we call FB.XFBML.parse? we don't want to do this at page load because it will happen automatically
if (doParse && FB && FB.XFBML && FB.XFBML.parse)
FB.XFBML.parse();
};
return this.each(function() {
var $container = $(this),
$clonedContainer = $container.clone();
// make sure there is a .fb-post element before we do anything.
if ( ! $container.find('div.fb-post').length) {
return false;
}
// execute once (document.ready) and do not call FB.XFBML.parse()
fixWidth($container, $clonedContainer, false);
// on window resize, update and fix..
$(window).on('resize', function() {
// only trigger fixWidth once after window has not been resized for 1 second
delayFireOnce(1000).done(function() {
fixWidth($container, $clonedContainer);
});
});
// helper function
var delayTimer;
var delayFireOnce = function(timeout) {
var d = $.Deferred();
clearTimeout(delayTimer);
t = setTimeout(function() {
d.resolve();
}, timeout);
return d.promise();
}; 
});
};  
})(jQuery);
(function($) {
    $(document).ready(function() {
        $('#post').autoResizeFbPost();
    });   
})(jQuery);
</script>

JavaScript Inheritance and the Prototype

You know inheritance, right? You know how in Java, for example, you can have one class inherit another and automatically get all the methods and variables of the parent class?

public class Mammal{
    public void breathe(){
        // do some breathing
    }
}
public class Cat extends Mammal{
    // now cat too can breathe!
}

Well, in Javascript, we have the same thing, just different. For starters, we don’t even have classes! Instead, we have something called the prototype. Here’s how we write the equivalent of the above Java code in Javascript

function Mammal(){
}
Mammal.prototype.breathe = function(){
    // do some breathing
}
function Cat(){
}
Cat.prototype = new Mammal()
Cat.prototype.constructor = Cat
// now cat too can breathe!

What’s this prototype? That’s just a bunch of gibberish!

Javascript is different from traditional object-oriented languages in that it usesprototype inheritance. In a nutshell, prototype inheritance in Javascript works like this:

1. An object has a number of properties. This includes any attributes or functions(methods).
2. An object has a special parent property, this is also called the prototype of the object(__proto__). An object inherits all the properties of its parent.
3. An object can override a property of its parent by setting the property on itself.
4. A constructor creates objects. Each constructor has an associated prototypeobject, which is simply another object.
5. When an object is created, it’s parent is set to the prototype object associated with the constructor that created it.

Okay! Now that you understand everything there is to know about prototype inheritance, let’s look at our Cat example more closely and break it down.

First, we create a constructor for Mammal

function Mammal(){
}

At this point, Mammal already has an associated prototype

Mammal.prototype
// {}

Let’s create an instance

var mammal = new Mammal()

Now, let’s verify the second law of prototype inheritence(it’s just the second bullet from the list)

mammal.__proto__ === Mammal.prototype
// true

Next, we add the breathe function to the prototype of Mammal

Mammal.prototype.breathe = function(){
    // do some breathing
}

At this point, mammal the instance can breathe

mammal.breathe()

because it inherits from Mammal.prototype. Next,

function Cat(){
}
Cat.prototype = new Mammal()

Cat constructor is created and we set Cat.prototype to a new instance of Mammal. Why do we do this?

var garfield = new Cat()
garfield.breathe()

because now any cat instance inherits Mammal and will therefore be able to breathe as well. Next,

Cat.prototype.constructor = Cat

Ensures that cats know that they are cats:

garfield.__proto__ === Cat.prototype
// true
Cat.prototype.constructor === Cat
// true
garfield instanceof Cat
// true

Each time you create a new instance of Cat, you create a 2-level chain, in thatgarfield is now parented by Cat.prototype which, since it is an instance ofMammal, is in turn parented by Mammal.prototype.

Now, guess who’s the parent of Mammal.prototype? Yeah, you guessed it,Object.prototype. So actually, it’s a 3-level chain

garfield -> Cat.prototype -> Mammal.prototype -> Object.prototype

You can add properties to any of garfield’s parents, and garfield would magically gain those properties too, even after garfield has already been created!

Cat.prototype.isCat = true
Mammal.prototype.isMammal = true
Object.prototype.isObject = true
garfield.isCat // true
garfield.isMammal // true
garfield.isObject // true

You can ask whether he has a given property

'isMammal' in garfield
// true

and you can also distinguish between own properties vs inherited properties

garfield.name = 'Garfield'
garfield.hasOwnProperty('name')
// true
garfield.hasOwnProperty('breathe')
// false

Relationship between C#, .NET, ASP, ASP.NET etc

The key points to take into account:

1. C# and C#.NET are the same thing... C#
2. .NET is, as you say, a library of code that .NET languages can talk to.
3. .NET languages come in different flavors such as: C#.NET, VB.NET, Managed C++, F#.
4. .NET languages compile to CIL ([Common Intermediate Language][1]) which means they all start "talking" the same language and can therefore inter operate.
5. ASP.NET is the portion of the .NET library used for making web sites. There are other subsections of ASP.NET like WebForms (the old way of making web pages) or the rapidly maturing MVC library that are worth looking at too.
6. Forms (old tech) or the new WPF (Windows Presentation Foundation) are the technologies you'd typically use in .NET to create what you know as traditional desktop applications.

One final thing I'd like to finish on is the difference between library and framework. In recent years these two terms have been used as those synonymous, however that is not the case. The easiest way I can think to differentiate the two is:

• A library contains many pieces of functionality that you may pick and choose from i.e. using one piece of technology doesn't mean you're locked into the rest. This means freedom, however you will have more work cut out for you.
• A framework however very much sets out how you will be working be providing a workflow that for better or worse is hard to change. This means rapid development/prototyping, but if significant changes are made in the future it may be impossible (or very time consuming) to implement them.

The project you're working on will depend on which choice you make.

Error starting Tomcat from NetBeans - '127.0.0.1*' is not recognized as an internal or external command

Change the following in <tomcat directory>/bin/catalina.bat

:noJuliConfig
set "JAVA_OPTS=%JAVA_OPTS% %LOGGING_CONFIG%"
..
:noJuliManager
set "JAVA_OPTS=%JAVA_OPTS% %LOGGING_MANAGER%"

to

:noJuliConfig
set JAVA_OPTS=%JAVA_OPTS% %LOGGING_CONFIG%
.. 
:noJuliManager
set JAVA_OPTS=%JAVA_OPTS% %LOGGING_MANAGER%

"Starting of Tomcat failed" message when trying to start tomcat from netbeans

This is a bug of netbeans. to resolve this do the following

Remove tcnative-1.dll from the apache-tomcat/bin folder in your installation.

Apparently the native connector is not playing well with the check that netbeans

uses to determine that the server is up and running. The bundled tomcat server

does not include the tcnative-1.dll. It's definitely not needed for development

purposes.

Struts Framework

This page will give you a short overview of Struts Framework and its main components.

What Is the Struts Framework?

The Struts Framework is a standard for developing well-architected Web applications. It has the following features:

• Open source
• Based on the Model-View-Controller (MVC) design paradigm, distinctly separating all three levels:
  • Model: application state
  • View: presentation of data (JSP, HTML)
  • Controller: routing of the application flow
• Implements the JSP Model 2 Architecture
• Stores application routing information and request mapping in a single core file, struts-config.xml

The Struts Framework, itself, only fills in the View and Controller layers. The Model layer is left to the developer.

Architecture Overview

All incoming requests are intercepted by the Struts servlet controller. The Struts Configuration file struts-config.xml is used by the controller to determine the routing of the flow. This flows consists of an alternation between two transitions:

From View to Action	A user clicks on a link or submits a form on an HTML or JSP page. The controller receives the request, looks up the mapping for this request, and forwards it to an action. The action in turn calls a Model layer (Business layer) service or function.
From Action to View	After the call to an underlying function or service returns to the action class, the action forwards to a resource in the View layer and a page is displayed in a web browser.

The diagram below describes the flow in more detail:

1. User clicks on a link in an HTML page.
2. Servlet controller receives the request, looks up mapping information in struts-config.xml, and routes to an action.
3. Action makes a call to a Model layer service.
4. Service makes a call to the Data layer (database) and the requested data is returned.
5. Service returns to the action.
6. Action forwards to a View resource (JSP page)
7. Servlet looks up the mapping for the requested resource and forwards to the appropriate JSP page.
8. JSP file is invoked and sent to the browser as HTML.
9. User is presented with a new HTML page in a web browser.

Struts Components

The Controller

This receives all incoming requests. Its primary function is the mapping of a request URI to an action class selecting the proper application module. It's provided by the framework.

The struts-config.xml File

This file contains all of the routing and configuration information for the Struts application. This XML file needs to be in the WEB-INF directory of the application.

Action Classes

It's the developer's responsibility to create these classes. They act as bridges between user-invoked URIs and business services. Actions process a request and return an ActionForward object that identifies the next component to invoke. They're part of the Controller layer, not the Model layer.

View Resources

View resources consist of Java Server Pages, HTML pages, JavaScript and Stylesheet files, Resource bundles, JavaBeans, and Struts JSP tags.

ActionForms

These greatly simplify user form validation by capturing user data from the HTTP request. They act as a "firewall" between forms (Web pages) and the application (actions). These components allow the validation of user input before proceeding to an Action. If the input is invalid, a page with an error can be displayed.

Model Components

The Struts Framework has no built-in support for the Model layer. Struts supports any model components:

• JavaBeans
• EJB
• CORBA
• JDO
• any other

Converting HTML into XLS using Javascript

JavaScript

<script src="http://code.jquery.com/jquery-latest.min.js" type="text/javascript"></script>
    <script type="text/javascript">
        var tableToExcel = (function () {
            var uri = 'data:application/vnd.ms-excel;base64,'
                , template = '<html xmlns:o="urn:schemas-microsoft-com:office:office" 
                xmlns:x="urn:schemas-microsoft-com:office:excel" 
                xmlns="http://www.w3.org/TR/REC-html40"><head>
                <!--[if gte mso 9]><xml><x:ExcelWorkbook><x:ExcelWorksheets>
                <x:ExcelWorksheet><x:Name>{worksheet}</x:Name>
                <x:WorksheetOptions><x:DisplayGridlines/></x:WorksheetOptions>
                </x:ExcelWorksheet></x:ExcelWorksheets></x:ExcelWorkbook>
                </xml><![endif]--></head><body>
                <table>{table}</table></body></html>'
                , base64 = function (s) { return window.btoa(unescape(encodeURIComponent(s))) }
                , format = function (s, c) { return s.replace(/{(\w+)}/g, function (m, p) { return c[p]; }) }
                return function (table, name) {
                if (!table.nodeType) table = document.getElementById(table)
                var ctx = { worksheet: name || 'Worksheet', table: table.innerHTML }
                window.location.href = uri + base64(format(template, ctx))
            }
        })()
    </script>

Sample HTML Code

<input type="button" onclick="tableToExcel('table', 'Example Table')" value="Export to Excel">
    <table id="table" summary="Code page support in different versions of MS Windows."

           .........................table design............................

    </table>
        

Converting HTML into CSV using Javascript

<!DOCTYPE>
<html>
    <head>
        <meta charset="utf-8">
        <meta name="viewport" content="width=device-width, initial-scale=1.0">
        <meta name="author" content="Adila Faruk">
         

        <title>Exporting Data to a CSV File</title>


        <style type="text/css">
            body{
                font-family: sans-serif;
                font-weight:300;
                padding-top:30px;
                color:#666;
            }
            .container{
                text-align:center;  
            }
            a{ color:#1C2045; font-weight:350;}
            table{
                font-weight:300;
                margin:0px auto;
                border: 1px solid #1C2045;
                padding:5px;
                color:#666;

            }
            th,td{ 
                border-bottom: 1px solid #dddddd;
                text-align:center;
                margin: 10px;
                padding:0 10px;
            }
            hr{ 
                border:0;
                border-top: 1px solid #E7C254;
                margin:20px auto;
                width:50%;
            }
            .button{
                background-color:#1C2045;
                color:#E7C254;
                padding:5px 20px;
                max-width: 300px;
                line-height:1.5em;
                text-align:center;
                margin:5px auto;
            }
            .button a{ color:#E7C254;}
            .refs{ display:block; margin:auto; text-align:left; max-width:500px; }
            .refs .label{  font-size:1.4em;}
            .refs > ul{ margin-top:10px; line-height:1.5em;}
        </style>
    </head>

    <body>
        <div class='container'> 
          <div id="dvData">
                <table>
                    <tr>
                        <th>Column One</th>
                        <th>Column Two</th>
                        <th>Column Three</th>
                    </tr>
                    <tr>
                        <td>Row 1 Col 1</td>
                        <td>Row 1 Col 2</td>
                        <td>Row 1 Col 3 </td>
                    </tr>
                    <tr>
                        <td>Row 2 Col 1</td>
                        <td>Row 2 Col 2</td>
                        <td>Row 2 Col 3</td>
                    </tr>
                    <tr>
                        <td>Row 3 Col 1</td>
                        <td>Row 3 Col 2</td>
                        <td>Row 3 Col 3</td>
                    </tr>
                </table>
            </div>
            <br/>
            <div class='button'>
                <a href="#" id ="export" role='button'>Click On This Here Link To Export The Table Data into a CSV File
                </a>
            </div>

            <hr/>
            <div class='refs'>
            <div class='label'>References</div>
            <ul>

            <li><a href="http://stackoverflow.com/questions/16078544/export-to-csv-using-jquery-and-html" target="_blank">Export to CSV using jQuery and HTML (Stack Overflow)</a>
            </li>
            <li> 
            <a href="http://adilapapaya.wordpress.com/2013/11/15/exporting-data-from-a-web-browser-to-a-csv-file-using-javascript/" target="_blank">adilapapaya.wordpress.com</a>
            </li>
            </ul>
            </div>
            <hr/>
        </div>

        <!-- Scripts ----------------------------------------------------------- -->
        <script type='text/javascript' src='https://code.jquery.com/jquery-1.11.0.min.js'></script>
        <!-- If you want to use jquery 2+: https://code.jquery.com/jquery-2.1.0.min.js -->
        <script type='text/javascript'>
        $(document).ready(function () {

            console.log("HELLO")
            function exportTableToCSV($table, filename) {
                var $headers = $table.find('tr:has(th)')
                    ,$rows = $table.find('tr:has(td)')

                    // Temporary delimiter characters unlikely to be typed by keyboard
                    // This is to avoid accidentally splitting the actual contents
                    ,tmpColDelim = String.fromCharCode(11) // vertical tab character
                    ,tmpRowDelim = String.fromCharCode(0) // null character

                    // actual delimiter characters for CSV format
                    ,colDelim = '","'
                    ,rowDelim = '"\r\n"';

                    // Grab text from table into CSV formatted string
                    var csv = '"';
                    csv += formatRows($headers.map(grabRow));
                    csv += rowDelim;
                    csv += formatRows($rows.map(grabRow)) + '"';

                    // Data URI
                    var csvData = 'data:application/csv;charset=utf-8,' + encodeURIComponent(csv);

                $(this)
                    .attr({
                    'download': filename
                        ,'href': csvData
                        //,'target' : '_blank' //if you want it to open in a new window
                });

                //------------------------------------------------------------
                // Helper Functions 
                //------------------------------------------------------------
                // Format the output so it has the appropriate delimiters
                function formatRows(rows){
                    return rows.get().join(tmpRowDelim)
                        .split(tmpRowDelim).join(rowDelim)
                        .split(tmpColDelim).join(colDelim);
                }
                // Grab and format a row from the table
                function grabRow(i,row){
                     
                    var $row = $(row);
                    //for some reason $cols = $row.find('td') || $row.find('th') won't work...
                    var $cols = $row.find('td'); 
                    if(!$cols.length) $cols = $row.find('th');  

                    return $cols.map(grabCol)
                                .get().join(tmpColDelim);
                }
                // Grab and format a column from the table 
                function grabCol(j,col){
                    var $col = $(col),
                        $text = $col.text();

                    return $text.replace('"', '""'); // escape double quotes

                }
            }


            // This must be a hyperlink
            $("#export").click(function (event) {
                // var outputFile = 'export'
                var outputFile = window.prompt("What do you want to name your output file (Note: This won't have any effect on Safari)") || 'export';
                outputFile = outputFile.replace('.csv','') + '.csv'
                 
                // CSV
                exportTableToCSV.apply(this, [$('#dvData>table'), outputFile]);
                
                // IF CSV, don't do event.preventDefault() or return false
                // We actually need this to be a typical hyperlink
            });
        });
    </script>
    </body>
</html>

Dynamic Table Populate and print using JavaScript

<style>
    #datacontainer {
        border: 5px!important;
    }
    #btnClick {
        float: right;
        margin-top: -30px;
    }
    table thead th { border-bottom: 1px solid #000; }
    table tfoot td { border-top: 1px solid #000; }
</style>
<button id="btnClick" type="button">Get Data</button>
<div class="clear-fix"></div>
<div id="main">
    <table id="datacontainer" width="100%">
        <thead>
            <tr>
                <th style="font-weight: bold; text-align: center; width: 50px;">Id</th>
                <th style="font-weight: bold; text-align: left; width: 50px; padding-left: 15px;">Name</th>
                <th style="font-weight: bold; text-align: right; width: 50px; padding-right: 15px;">Amount</th>
                <th style="font-weight: bold; text-align: left; width: 50px; padding-left: 15px;">Address</th>
            </tr>
        </thead>
        <tbody id="hook">
            <tr id="template" hidden="hidden">
                <td id="id" style="text-align: center; width:50px;"></td>
                <td id="name" style="text-align: left; width:50px; padding-left: 15px;"></td>
                <td id="amt" style="text-align: right; width:50px; padding-right: 10px;"></td>
                <td id="add" style="text-align: left; width:50px; padding-left: 15px;"></td>
            </tr>
        </tbody>
        <tfoot>
            <tr>
                <td colspan=4></td>
            </tr>
        </tfoot>
    </table>
</div>
<script type="text/javascript">
    $(function () {
        var url = '@Url.Action("GetData")';
        $('#btnClick').click(function (event) {
            event.preventDefault();
            var template = $('#template');
            $('#hook').html(template);
            $.ajax(url, {
                dataType: 'json'
            }).done(function (data) {
                $.each(data.data, function (key, value) {
                    var row = $('#template').clone();
                    $(row).attr('id', 'id' + key);
                    $(row).removeAttr('hidden');
                    polpulateData(row, value);
                    $(row).appendTo($('#hook'));
                });
                var printData = $('#main').html();
                $(printData, '#btnClick').css('display', 'none');
                popup(printData);
            });
            return false;
        });

        function polpulateData(row, data) {
            $(row).find('#id').text(data.Id);
            $(row).find('#name').text(data.Name);
            $(row).find('#amt').text(data.Amount);
            $(row).find('#add').text(data.Address);
        }

        function popup(data) {
            var mywindow = window.open('', 'Sample', 'height=400,width=600');
            mywindow.document.write('<html><head><title>Sample</title>');
            /*optional stylesheet*/ //mywindow.document.write('<link rel="stylesheet" href="main.css" type="text/css" />');
            mywindow.document.write('</head><body >');
            mywindow.document.write(data);
            mywindow.document.write('</body></html>');
            mywindow.focus();
            mywindow.print();
            //mywindow.close();

            return true;
        }
    });
</script>

Windows finding processes running on certain ports:

C:\WINDOWS\system32> netstat -ano | findstr 8080 -----> any port you want to get the status about

Rightmost column is PID.

To kill any process use the following command:

C:\WINDOWS\system32> taskkill /F /PID 4184 -----> any process you want to kill