ADO.NET

ADO.NET is an object-oriented set of libraries that allows you to interact with data sources. Commonly, the data source is a database, but it could also be a text file, an Excel spreadsheet, or an XML file. For the purposes of this tutorial, we will look at ADO.NET as a way to interact with a data base.

As you are probably aware, there are many different types of databases available. For example, there is Microsoft SQL Server, Microsoft Access, Oracle, Borland Interbase, and IBM DB2, just to name a few. To further refine the scope of this tutorial, all of the examples will use SQL Server. 

Data Providers

We know that ADO.NET allows us to interact with different types of data sources and different types of databases. However, there isn't a single set of classes that allow you to accomplish this universally. Since different data sources expose different protocols, we need a way to communicate with the right data source using the right protocol Some older data sources use the ODBC protocol, many newer data sources use the OleDb protocol, and there are more data sources every day that allow you to communicate with them directly through .NET ADO.NET class libraries.

ADO.NET provides a relatively common way to interact with data sources, but comes in different sets of libraries for each way you can talk to a data source. These libraries are called Data Providers and are usually named for the protocol or data source type they allow you to interact with. Table 1 lists some well known data providers, the API prefix they use, and the type of data source they allow you to interact with.

Provider Name	API prefix	Data Source Description
ODBC Data Provider	Odbc	Data Sources with an ODBC interface. Normally older data bases.
OleDb Data Provider	OleDb	Data Sources that expose an OleDb interface, i.e. Access or Excel.
Oracle Data Provider	Oracle	For Oracle Databases.
SQL Data Provider	Sql	For interacting with Microsoft SQL Server.
Borland Data Provider	Bdp	Generic access to many databases such as Interbase, SQL Server, IBM DB2, and Oracle.

 

ADO.NET Objects

ADO.NET includes many objects you can use to work with data. This section introduces some of the primary objects you will use. Over the course of this tutorial, you'll be exposed to many more ADO.NET objects from the perspective of how they are used in a particular lesson. The objects below are the ones you must know. Learning about them will give you an idea of the types of things you can do with data when using ADO.NET.

The SqlConnection Object

To interact with a database, you must have a connection to it. The connection helps identify the database server, the database name, user name, password, and other parameters that are required for connecting to the data base. A connection object is used by command objects so they will know which database to execute the command on.

The SqlCommand Object

The process of interacting with a database means that you must specify the actions you want to occur. This is done with a command object. You use a command object to send SQL statements to the database. A command object uses a connection object to figure out which database to communicate with. You can use a command object alone, to execute a command directly, or assign a reference to a command object to an SqlDataAdapter, which holds a set of commands that work on a group of data as described below.

The SqlDataReader Object

Many data operations require that you only get a stream of data for reading. The data reader object allows you to obtain the results of a SELECT statement from a command object. For performance reasons, the data returned from a data reader is a fast forward-only stream of data. This means that you can only pull the data from the stream in a sequential manner This is good for speed, but if you need to manipulate data, then a DataSet is a better object to work with.

The DataSet Object

DataSet objects are in-memory representations of data. They contain multiple Datatable objects, which contain columns and rows, just like normal database tables. You can even define relations between tables to create parent-child relationships. The DataSet is specifically designed to help manage data in memory and to support disconnected operations on data, when such a scenario make sense. The DataSet is an object that is used by all of the Data Providers, which is why it does not have a Data Provider specific prefix.

The SqlDataAdapter Object

Sometimes the data you work with is primarily read-only and you rarely need to make changes to the underlying data source Some situations also call for caching data in memory to minimize the number of database calls for data that does not change. The data adapter makes it easy for you to accomplish these things by helping to manage data in a disconnected mode. The data adapter fills a DataSet object when reading the data and writes in a single batch when persisting changes back to the database. A data adapter contains a reference to the connection object and opens and closes the connection automatically when reading from or writing to the database. Additionally, the data adapter contains command object references for SELECT, INSERT, UPDATE, and DELETE operations on the data. You will have a data adapter defined for each table in a DataSet and it will take care of all communication with the database for you. All you need to do is tell the data adapter when to load from or write to the database.

Summary

ADO.NET is the .NET technology for interacting with data sources. You have several Data Providers, which allow communication with different data sources, depending on the protocols they use or what the database is. Regardless, of which Data Provider used, you'll use a similar set of objects to interact with a data source. The SqlConnection object lets you manage a connection to a data source. SqlCommand objects allow you to talk to a data source and send commands to it. To have fast forward-only read access to data, use the SqlDataReader. If you want to work with disconnected data, use a DataSet and implement reading and writing to/from the data source with a SqlDataAdapter.

Introduction

A SqlCommand object allows you to specify what type of interaction you want to perform with a database. For example, you can do select, insert, modify, and delete commands on rows of data in a database table. The SqlCommand object can be used to support disconnected data management scenarios, but in this lesson we will only use the SqlCommand object alone. A later lesson on the SqlDataAdapter will explain how to implement an application that uses disconnected data. This lesson will also show you how to retrieve a single value from a database, such as the number of records in a table.

Creating a SqlCommand Object

Similar to other C# objects, you instantiate a SqlCommand object via the new instance declaration, as follows:

    SqlCommand cmd = new SqlCommand("select CategoryName from Categories", conn);

The line above is typical for instantiating a SqlCommand object. It takes a string parameter that holds the command you want to execute and a reference to a SqlConnection object. SqlCommand has a few overloads, which you will see in the examples of this tutorial.

Querying Data

When using a SQL select command, you retrieve a data set for viewing. To accomplish this with a SqlCommand object, you would use the ExecuteReader method, which returns a SqlDataReader object. We'll discuss the SqlDataReader in a future lesson. The example below shows how to use the SqlCommand object to obtain a SqlDataReader object:
// 1. Instantiate a new command with a query and connection
SqlCommand cmd = new SqlCommand("select CategoryName from Categories", conn);

// 2. Call Execute reader to get query results
SqlDataReader rdr = cmd.ExecuteReader();
In the example above, we instantiate a SqlCommand object, passing the command string and connection object to the constructor. Then we obtain a SqlDataReader object by calling the ExecuteReader method of the SqlCommand object, cmd.
This code is part of the ReadData method of Listing 1 in the Putting it All Together section later in this lesson.

Inserting Data

To insert data into a database, use the ExecuteNonQuery method of the SqlCommand object. The following code shows how to insert data into a database table:
// prepare command string
 string insertString = @"
     insert into Categories
     (CategoryName, Description)
     values ('Miscellaneous', 'Whatever doesn''t fit elsewhere')";

 // 1. Instantiate a new command with a query and connection
 SqlCommand cmd = new SqlCommand(insertString, conn);

 // 2. Call ExecuteNonQuery to send command
 cmd.ExecuteNonQuery();
The SqlCommand instantiation is just a little different from what you've seen before, but it is basically the same. Instead of a literal string as the first parameter of the SqlCommand constructor, we are using a variable, insertString. The insertString variable is declared just above the SqlCommand declaration.
Notice the two apostrophes ('') in the insertString text for the word "doesn''t". This is how you escape the apostrophe to get the string to populate column properly.
Another observation to make about the insert command is that we explicitly specified the columns CategoryName and Description. The Categories table has a primary key field named CategoryID. We left this out of the list because SQL Server will add this field itself. trying to add a value to a primary key field, such as CategoryID, will generate an exception.
To execute this command, we simply call the ExecuteNonQuery method on the SqlCommand instance, cmd.
This code is part of the Insertdata method of Listing 1 in the Putting it All Together section later in this lesson.

Updating Data

The ExecuteNonQuery method is also used for updating data. The following code shows how to update data:
// prepare command string
 string updateString = @"
     update Categories
     set CategoryName = 'Other'
     where CategoryName = 'Miscellaneous'";
 
 // 1. Instantiate a new command with command text only
 SqlCommand cmd = new SqlCommand(updateString);
 
 // 2. Set the Connection property
 cmd.Connection = conn;
 
 // 3. Call ExecuteNonQuery to send command
 cmd.ExecuteNonQuery();
Again, we put the SQL command into a string variable, but this time we used a different SqlCommand constructor that takes only the command. In step 2, we assign the SqlConnection object, conn, to the Connection property of the SqlCommand object, cmd.
This could have been done with the same constructor used for the insert command, with two parameters. It demonstrates that you can change the connection object assigned to a command at any time.
The ExecuteNonQuery method performs the update command.
This code is part of the UpdateData method of Listing 1 in the Putting it All Together section later in this lesson.

Deleting Data

You can also delete data using the ExecuteNonQuery method. The following example shows how to delete a record from a database with the ExecuteNonQuery method:
// prepare command string
 string deleteString = @"
     delete from Categories
     where CategoryName = 'Other'";
 
 // 1. Instantiate a new command
 SqlCommand cmd = new SqlCommand();
 
 // 2. Set the CommandText property
 cmd.CommandText = deleteString;
 
 // 3. Set the Connection property
 cmd.Connection = conn;
 
 // 4. Call ExecuteNonQuery to send command
 cmd.ExecuteNonQuery();
This example uses the SqlCommand constructor with no parameters. Instead, it explicity sets the CommandText and Connection properties of the SqlCommand object, cmd.
We could have also used either of the two previous SqlCommand constructor overloads, used for the insert or update command, with the same result. This demonstrates that you can change both the command text and the connection object at any time.
The ExecuteNonQuery method call sends the command to the database.
This code is part of the DeleteData method of Listing 1 in the Putting it All Together section later in this lesson.

Getting Single values

Sometimes all you need from a database is a single value, which could be a count, sum, average, or other aggregated value from a data set. Performing an ExecuteReader and calculating the result in your code is not the most efficient way to do this. The best choice is to let the database perform the work and return just the single value you need. The following example shows how to do this with the ExecuteScalar method:
// 1. Instantiate a new command
 SqlCommand cmd = new SqlCommand("select count(*) from Categories", conn);
 
 // 2. Call ExecuteNonQuery to send command
 int count = (int)cmd.ExecuteScalar();
The query in the SqlCommand constructor obtains the count of all records from the Categories table. This query will only return a single value. The ExecuteScalar method in step 2 returns this value. Since the return type of ExecuteScalar is type object, we use a cast operator to convert the value to int.
This code is part of the GetNumberOfRecords method of Listing 1 in the Putting it All Together section later in this lesson.

Putting it All Together

For simplicity, we showed snippets of code in previous sections to demonstrate the applicable techniques. It is also useful to have an entire code listing to see how this code is used in a working program. Listing 1 shows all of the code used in this example, along with a driver in the Main method to produce formatted output.

Listing 1. SqlConnection Demo

 using System;
 using System.Data;
 using System.Data.SqlClient;

 /// <summary>
 /// Demonstrates how to work with SqlCommand objects
 /// </summary>
 class SqlCommandDemo
 {
     SqlConnection conn;
 
     public SqlCommandDemo()
     {
         // Instantiate the connection
         conn = new SqlConnection(
            "Data Source=(local);Initial Catalog=Northwind;Integrated Security=SSPI");
     }
 
     // call methods that demo SqlCommand capabilities
     static void Main()
     {
         SqlCommandDemo scd = new SqlCommandDemo();

         Console.WriteLine();
         Console.WriteLine("Categories Before Insert");
         Console.WriteLine("------------------------");
 
         // use ExecuteReader method
         scd.ReadData();
 
         // use ExecuteNonQuery method for Insert
         scd.Insertdata();
         Console.WriteLine();
         Console.WriteLine("Categories After Insert");
         Console.WriteLine("------------------------------");

        scd.ReadData();

         // use ExecuteNonQuery method for Update
         scd.UpdateData();

         Console.WriteLine();
         Console.WriteLine("Categories After Update");
         Console.WriteLine("------------------------------");

         scd.ReadData();

         // use ExecuteNonQuery method for Delete
         scd.DeleteData();

         Console.WriteLine();
         Console.WriteLine("Categories After Delete");
         Console.WriteLine("------------------------------");

         scd.ReadData();

         // use ExecuteScalar method
         int numberOfRecords = scd.GetNumberOfRecords();

         Console.WriteLine();
         Console.WriteLine("Number of Records: {0}", numberOfRecords);
     }

     /// <summary>
     /// use ExecuteReader method
     /// </summary>
     public void ReadData()
     {
        SqlDataReader rdr = null;
 
         try
         {
             // Open the connection
             conn.Open();
 
             // 1. Instantiate a new command with a query and connection
             SqlCommand cmd = new SqlCommand("select CategoryName from Categories", conn);
 
             // 2. Call Execute reader to get query results
             rdr = cmd.ExecuteReader();

             // print the CategoryName of each record
             while (rdr.Read())
             {
                 Console.WriteLine(rdr[0]);
             }
         }
         finally
         {
             // close the reader
             if (rdr != null)
             {
                 rdr.Close();
             }
 
             // Close the connection
             if (conn != null)
             {
                 conn.Close();
             }
         }
     }

     /// <summary>
     /// use ExecuteNonQuery method for Insert
     /// </summary>
     public void Insertdata()
     {
         try
         {
             // Open the connection
             conn.Open();
 
             // prepare command string
             string insertString = @"
                 insert into Categories
                 (CategoryName, Description)
                 values ('Miscellaneous', 'Whatever doesn''t fit elsewhere')";
 
             // 1. Instantiate a new command with a query and connection
             SqlCommand cmd = new SqlCommand(insertString, conn);
 
             // 2. Call ExecuteNonQuery to send command
             cmd.ExecuteNonQuery();
         }
         finally
         {
             // Close the connection
             if (conn != null)
             {
                 conn.Close();
             }
         }
     }
 
     /// <summary>
     /// use ExecuteNonQuery method for Update
     /// </summary>
     public void UpdateData()
     {
         try
         {
             // Open the connection
             conn.Open();
 
             // prepare command string
             string updateString = @"
                 update Categories
                 set CategoryName = 'Other'
                 where CategoryName = 'Miscellaneous'";
 
             // 1. Instantiate a new command with command text only
             SqlCommand cmd = new SqlCommand(updateString);

             // 2. Set the Connection property
             cmd.Connection = conn;
 
             // 3. Call ExecuteNonQuery to send command
             cmd.ExecuteNonQuery();
        }
         finally
         {
             // Close the connection
             if (conn != null)
             {
                 conn.Close();
             }
         }
     }
 
     /// <summary>
     /// use ExecuteNonQuery method for Delete
     /// </summary>
     public void DeleteData()
     {
         try
         {
             // Open the connection
             conn.Open();
 
             // prepare command string
             string deleteString = @"
                 delete from Categories
                 where CategoryName = 'Other'";
 
             // 1. Instantiate a new command
             SqlCommand cmd = new SqlCommand();
 
             // 2. Set the CommandText property
             cmd.CommandText = deleteString;
 
             // 3. Set the Connection property
             cmd.Connection = conn;
 
             // 4. Call ExecuteNonQuery to send command
             cmd.ExecuteNonQuery();
         }
         finally
         {
             // Close the connection
             if (conn != null)
             {
                 conn.Close();
             }
         }
     }

     /// <summary>
     /// use ExecuteScalar method
     /// </summary>
     /// <returns>number of records</returns>
     public int GetNumberOfRecords()
     {
         int count = -1;
 
         try
         {
             // Open the connection
             conn.Open();
 
             // 1. Instantiate a new command
             SqlCommand cmd = new SqlCommand("select count(*) from Categories", conn);
 
             // 2. Call ExecuteScalar to send command
             count = (int)cmd.ExecuteScalar();
         }
         finally
         {
            // Close the connection
             if (conn != null)
             {
                 conn.Close();
             }
         }
         return count;
     }
 }
In Listing 1, the SqlConnection object is instantiated in the SqlCommandDemo structure. This is okay because the object itself will be cleaned up when the CLR garbage collector executes. What is important is that we close the connection when we are done using it. This program opens the connection in a try block and closes it in a finally block in each method.
The ReadData method displays the contents of the CategoryName column of the Categories table. We use it several times in the Main method to show the current status of the Categories table, which changes after each of the insert, update, and delete commands. Because of this, it is convenient to reuse to show you the effects after each method call.

Functions used with Console Class in C#

class Program

    {

        static void Main(string[] args)

        {

            int a;

            

            ConsoleKeyInfo keypress = Console.ReadKey();

            if (keypress.Key == ConsoleKey.Escape)

            {

                Console.WriteLine("You are pressed Escape");

            }



            a = keypress.KeyChar;

            if (a == 13)

            {

                Console.WriteLine("You are pressed Enter");

            }





            keypress = Console.ReadKey();

            if (keypress.Key == ConsoleKey.X &&

                keypress.Modifiers == ConsoleModifiers.Control)

            {

                Console.WriteLine("You are pressed CTRL+X");

            }

            Console.Read();



        }

Introduction To Web

The World Wide Web (abbreviated as WWW or W3, commonly known as the Web, or the "Information Superhighway"), is a system of interlinked hypertext documents accessed via the Internet. With a web browser, one can view web pages that may contain text, images, videos, and other multimedia, and navigate between them via hyperlinks.


A website, also written as Web site, web site, or simply site, is a set of related web pages containing content (media) such as text, image, video, audio, etc. A website is hosted on at least one web server, accessible via a network such as the Internet or a private local area network through an Internet address known as a Uniform Resource Locator. All publicly accessible websites collectively constitute the World Wide Web.
A webpage is a document, typically written in plain text interspersed with formatting instructions of Hypertext Markup Language (HTML, XHTML). A webpage may incorporate elements from other websites with suitable markup anchors.

Static website
A static website is one that has web pages stored on the server in the format that is sent to a client web browser. It is primarily coded in Hypertext Markup Language (HTML).
Simple forms or marketing examples of websites, such as classic website, a five-page website or a brochure website are often static websites, because they present pre-defined, static information to the user. This may include information about a company and its products and services through text, photos, animations, audio/video and interactive menus and navigation.


Dynamic website
A dynamic website is one that changes or customizes itself frequently and automatically, based on certain criteria.
Dynamic websites can have two types of dynamic activity: Code and Content. Dynamic code is invisible or behind the scenes and dynamic content is visible or fully displayed.
Dynamic code
The first type is a web page with dynamic code. The code is constructed dynamically on the fly using active programming language instead of plain, static HTML.
A website with dynamic code refers to its construction or how it is built, and more specifically refers to the code used to create a single web page. A dynamic web page is generated on the fly by piecing together certain blocks of code, procedures or routines. A dynamically-generated web page would recall various bits of information from a database and put them together in a pre-defined format to present the reader with a coherent page. It interacts with users in a variety of ways including by reading cookies recognizing users' previous history, session variables, server side variables etc., or by using direct interaction (form elements, mouse overs, etc.). A site can display the current state of a dialogue between users, monitor a changing situation, or provide information in some way personalized to the requirements of the individual user.

Dynamic content
The second type is a website with dynamic content displayed in plain view. Variable content is displayed dynamically on the fly based on certain criteria, usually by retrieving content stored in a database.
A website with dynamic content refers to how its messages, text, images and other information are displayed on the web page, and more specifically how its content changes at any given moment. The web page content varies based on certain criteria, either pre-defined rules or variable user input. For example, a website with a database of news articles can use a pre-defined rule which tells it to display all news articles for today's date. This type of dynamic website will automatically show the most current news articles on any given date. Another example of dynamic content is when a retail website with a database of media products allows a user to input a search request for the keyword Beatles. In response, the content of the web page will spontaneously change the way it looked before, and will then display a list of Beatles products like CDs, DVDs and books.


Webpages are accessed and transported with the Hypertext Transfer Protocol (HTTP), which may optionally employ encryption (HTTP Secure, HTTPS) to provide security and privacy for the user of the webpage content. The user's application, often a web browser, renders the page content according to its HTML markup instructions onto a display terminal.
The pages of a website can usually be accessed from a simple Uniform Resource Locator (URL) called the web address. The URLs of the pages organize them into a hierarchy, although hyperlinking between them conveys the reader's perceived site structure and guides the reader's navigation of the site which generally includes a home page with most of the links to the site's web content, and a supplementary about, contact and link page.


A web application is an application that is accessed over a network such as the Internet or an intranet. The term may also mean a computer software application that is coded in a browser-supported language (such as JavaScript, combined with a browser-rendered markup language like HTML) and reliant on a common web browser to render the application executable.

A web browser is a software application for retrieving, presenting, and traversing information resources on the World Wide Web. An information resource is identified by a Uniform Resource Identifier (URI) and may be a web page, image, video, or other piece of content.Hyperlinks present in resources enable users easily to navigate their browsers to related resources. A web browser can also be defined as an application software or program designed to enable users to access, retrieve and view documents and other resources on the Internet.

Web server can refer to either the hardware (the computer) or the software (the computer application) that helps to deliver Web content that can be accessed through the Internet.The most common use of web servers is to host websites, but there are other uses such as gaming, data storage or running enterprise applications.


A web hosting service is a type of Internet hosting service that allows individuals and organizations to make their website accessible via the World Wide Web.In order to publish a website online, you need a Web host. The Web host stores all the pages of your website and makes them available to computers connected to the Internet. The domain name, such as "sony.com," is actually linked to an IP address that points to a specific computer. When somebody enters your domain name into their browser's address field, the IP address is located and Web site is loaded from your Web host.

The term Web services describes a standardized way of integrating Web-based applications using the XML, SOAP, WSDL and UDDI open standards over an Internet protocol backbone. XML is used to tag the data, SOAP is used to transfer the data, WSDL is used for describing the services available and UDDI is used for listing what services are available. Used primarily as a means for businesses to communicate with each other and with clients, Web services allow organizations to communicate data without intimate knowledge of each other's IT systems behind the firewall

.Net Introduction

The Microsoft .Net Framework is a platform that provides tools and technologies you need to build Networked Applications as well as Distributed Web Services and Web Applications. The .Net Framework provides the necessary compile time and run-time foundation to build and run any language that conforms to the Common Language Specification (CLS).The main two components of .Net Framework are Common Language Runtime (CLR) and .Net Framework Class Library (FCL).

Microsoft Visual Studio is an integrated development environment (IDE) from Microsoft. It is used to develop console and graphical user interface applications along with Windows Forms applications, web sites, web applications, and web services in both native code together with managed code for all platforms supported by Microsoft Windows, Windows Mobile, Windows CE, .NET Framework, .NET Compact Framework and Microsoft Silverlight.
Visual Studio includes a code editor supporting IntelliSense as well as code refactoring. The integrated debugger works both as a source-level debugger and a machine-level debugger. Other built-in tools include a forms designer for building GUI applications, web designer, class designer, and database schema designer.

Microsoft started the development on the .NET Framework in the late 1990s originally under the name of Next Generation Windows Services (NGWS). By late 2000 the first beta versions of .NET 1.0 were released.

Version 3.0 of the .NET Framework is included with Windows Server 2008 and Windows Vista. Version 3.5 is included with Windows 7, and can also be installed on Windows XP and the Windows Server 2003 family of operating systems. On 12 April 2010, .NET Framework 4 was released alongside Visual Studio 2010.

The .NET Framework family also includes two versions for mobile or embedded device use. A reduced version of the framework, the .NET Compact Framework, is available on Windows CE platforms, including Windows Mobile devices such as smartphones. Additionally, the .NET Micro Framework is targeted at severely resource-constrained devices.

Version	Version Number	Release Date	Visual Studio	Default in Windows
1.0	1.0.3705.0	2002-02-13	Visual Studio .NET	Windows XP Tablet and Media Center Editions.
1.1	1.1.4322.573	2003-04-24	Visual Studio .NET 2003	Windows Server 2003
2.0	2.0.50727.42	2005-11-07	Visual Studio 2005	Windows Server 2003 R2
3.0	3.0.4506.30	2006-11-06		Windows Vista, Windows Server 2008
3.5	3.5.21022.8	2007-11-19	Visual Studio 2008	Windows 7, Windows Server 2008 R2
4.0	4.0.30319.1	2010-04-12	Visual Studio 2010	Windows 7(Recommended)
4.5	4.5.40805	2012-02-29 (consumer preview)	Visual Studio '11'	Windows 8, Windows Server 8

Design features

Interoperability

Because computer systems commonly require interaction between newer and older applications, the .NET Framework provides means to access functionality implemented in programs that execute outside the .NET environment. Access to COM components is provided in the System.Runtime.InteropServices and System.EnterpriseServices namespaces of the framework; access to other functionality is provided using the P/Invoke feature.

Common Language Runtime Engine

The Common Language Runtime (CLR) is the execution engine of the .NET Framework. All .NET programs execute under the supervision of the CLR, guaranteeing certain properties and behaviors in the areas of memory management, security, and exception handling.

Language Independence

The .NET Framework introduces a Common Type System, or CTS. The CTS specification defines all possible datatypes and programming constructs supported by the CLR and how they may or may not interact with each other conforming to the Common Language Infrastructure (CLI) specification. Because of this feature, the .NET Framework supports the exchange of types and object instances between libraries and applications written using any conforming .NET language.

Base Class Library

The Base Class Library (BCL), part of the Framework Class Library (FCL), is a library of functionality available to all languages using the .NET Framework. The BCL provides classes that encapsulate a number of common functions, including file reading and writing, graphic rendering, database interaction, XML document manipulation, and so on.

Simplified Deployment

The .NET Framework includes design features and tools which help manage the installation of computer software to ensure it does not interfere with previously installed software, and it conforms to security requirements.

Security

The design is meant to address some of the vulnerabilities, such as buffer overflows, which have been exploited by malicious software. Additionally, .NET provides a common security model for all applications.

Portability

While Microsoft has never implemented the full framework on any system except Microsoft Windows, the framework is engineered to be platform agnostic, and cross-platform implementations are available for other operating systems (see Silverlight and the Alternative implementations section below). Microsoft submitted the specifications for the Common Language Infrastructure (which includes the core class libraries, Common Type System, and the Common Intermediate Language), the C# language and the C++/CLI language to both ECMA and the ISO, making them available as official standards. This makes it possible for third parties to create compatible implementations of the framework and its languages on other platforms.

 

Count Number of Visitors in WebSite using ASP.Net and C#

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Write Code in Global.asax file

<%@ Application Language="C#" %> <script runat="server"> public static int count = 0; void Application_Start(object sender, EventArgs e) { Application["myCount"] = count; // Code that runs on application startup } void Application_End(object sender, EventArgs e) { // Code that runs on application shutdown } void Application_Error(object sender, EventArgs e) { // Code that runs when an unhandled error occurs } void Session_Start(object sender, EventArgs e) { count = Convert.ToInt32(Application["myCount"]); Application["myCount"] = count + 1; // Code that runs when a new session is started } void Session_End(object sender, EventArgs e) { // Code that runs when a session ends. // Note: The Session_End event is raised only when the sessionstate mode // is set to InProc in the Web.config file. If session mode is set to StateServer // or SQLServer, the event is not raised. } </script>

.CS Code:

using System; using System.Collections; using System.Configuration; using System.Data; using System.Linq; using System.Web; using System.Web.Security; using System.Web.UI; using System.Web.UI.HtmlControls; using System.Web.UI.WebControls; using System.Web.UI.WebControls.WebParts; using System.Xml.Linq; public partial class Hitcounter : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { int a; a = Convert.ToInt32((Application["myCount"])); Label1.Text = Convert.ToString(a); if (a < 10) Label1.Text = "000" + Label1.Text; else if (a < 100) Label1.Text = "00" + Label1.Text; else if (a < 1000) Label1.Text = "0" + Label1.Text; } }

Disabling the back button Of Browser using ASP.NET

How to disable browser's Back button in ASP.NET

Almost every ASP.NET developer face this problem at least once in his entire career. There could be numerous reasons for disabling the browser's back button. The site is secure and the user should not be allowed to go back to the previous page, for online exams site the student should be not allowed to view the question once answered etc could be the reasons for disabling the back button.
What does the browser back button actually do?
The browser maintains a cache of the pages that are visited by the user. Once the user clicks on the back button, the browser flushes the cached version of the page. Now to avoid this situation we can think of two solutions
1. Whenever the user clicks on the "back" button, again redirect the user to the "next" page using the JavaScript: history.forward(1). This JavaScript needs to be written on the onload JavaScript event of the web page. Thus the user will never be able to come to the previous page. But this is not a reliable technique since some of the browser's do not invoke the onload function on pressing the "Back" button.
2. Another solution is to avoid the browser maintaining the cache of the pages that a user visits. Yes, this can be achieved through AsP.NET server side coding. Add the following code to the Page_Load event of ASP.NET web page or MasterPage:

// Disable the Cache
Response.Buffer= true;
Response.ExpiresAbsolute=DateTime.Now.AddDays(-1d);
Response.Expires =-1500;
Response.CacheControl = “no-cache”;

// Check for your SessionID
if(Session["SessionId"] == null)
{
   Response.Redirect (”Home.aspx”);
}

This code will disable the cache for the current page. The pages contents are maintained in memory i.e. in buffer. Once the user logout the session and buffer will be cleared. As we are not maintaining the cache for the page, the back button will not work anyways. It means we have successfully disabled the Back button.

FileUpload control in ASP.NET

With ASP.NET, accepting file uploads from users has become extremely easy. With the FileUpload control, it can be done with a small amount of code lines, as you will see in the following example. However, please notice that there are security concerns to to consider when accepting files from users! Here is the markup required:

<form id="form1" runat="server">
    <asp:FileUpload id="FileUploadControl" runat="server" />
    <asp:Button runat="server" id="UploadButton" text="Upload" 

onclick="UploadButton_Click" />
    <br /><br />
    <asp:Label runat="server" id="StatusLabel" text="Upload status: " />
</form>

And here is the CodeBehind code required to handle the upload:

protected void UploadButton_Click(object sender, EventArgs e)
{
    if(FileUploadControl.HasFile)
    {
        try
        {
            string filename = Path.GetFileName(FileUploadControl.FileName);
            FileUploadControl.SaveAs(Server.MapPath("~/") + filename);
            StatusLabel.Text = "Upload status: File uploaded!";
        }
        catch(Exception ex)
        {
            StatusLabel.Text = "Upload status: The file could not be uploaded.

 The following error occured: " + ex.Message;
        }
    }
}

As you can see, it's all relatively simple. Once the UploadButton is clicked, we check to see if a file has been specified in the upload control. If it has, we use the FileUpload controls SaveAs method to save the file. We use the root of our project (we use the MapPath method to get this) as well as the name part of the path which the user specified. If everything goes okay, we notify the user by setting the Text property of the StatusLabel - if not, an exception will be thrown, and we notify the user as well.

This example will get the job done, but as you can see, nothing is checked. The user can upload any kind of file, and the size of the file is only limited by the server configuration. A more robust example could look like this:

protected void UploadButton_Click(object sender, EventArgs e)
{
    if(FileUploadControl.HasFile)
    {
        try
        {
            if(FileUploadControl.PostedFile.ContentType == "image/jpeg")
            {
                if(FileUploadControl.PostedFile.ContentLength < 102400)
                {
                    string filename = Path.GetFileName(FileUploadControl.FileName);
                    FileUploadControl.SaveAs(Server.MapPath("~/") + filename);
                    StatusLabel.Text = "Upload status: File uploaded!";
                }
                else
                    StatusLabel.Text = "Upload status: The file has to be less 

than 100 kb!";
            }
            else
                StatusLabel.Text = "Upload status: Only JPEG files are accepted!";
        }
        catch(Exception ex)
        {
            StatusLabel.Text = "Upload status: The file could not be uploaded. 

The following error occured: " + ex.Message;
        }
    }
}

Here we use the two properties, ContentLength and ContentType, to do some basic checking of the file which the user is trying to upload. The status messages should clearly indicate what they are all about, and

you can change them to fit your needs.