ASP.NET is tool for creating Web Application.
ASP.NET is Server Side Scripting technology.
ASP.Net is a part of Microsoft .Net framework.
Like ASP, ASP.NET also runs inside IIS.
When browser requests an ASP.NET file, IIS passes the request to ASP.NET engine which after having executed the script sends file back to browser as a simple HTML page.
ASP.NET is not backward compatible with classic ASP.
Unlike interpreted classic ASP, ASP.NET is compiled CLR code.
Being part of CLR, it has advantages of early binding, JIT compilation, caching services, Garbage collection etc.
ASP.NET uses ADO.NET for data access and well integrated with VB.NET, C#.Net, Jscript etc.
ASP.NET provides two sets of controls - HTML and Server control.
ASP.NET employs a text-based configuration settings, no need to restart server in case of change in setting.
ASP.NET executes new code on request, no need to restart server in case of change in code.
ASP.NET is the platform to create Web applications and Web services.
ASP.NET runs under IIS.
It is tightly integrated with the Microsoft server, programming, data access, and security tools.
ASP.NET is part of the .NET Framework and is made up of several components like Visual Studio .NET Web development tools, System.Web namespaces, Server and HTML controls.
VS.NET Web development tools: Tools for designing Web pages and application templates, project management, and deployment tools for Web applications.
System.Web namespaces: Part of the .NET Framework that include classes.
Server and HTML controls: User-interface components.
Advantages of ASP.NET
Executable of Web application is compiled that runs faster than interpreted scripts,
Automatic state management for controls,
Access to the .NET Framework,
Introduction of VB.Net that is evolution version of VB, fully support object-oriented Programming,
New Visual C# programming language,
The ability to create new, customized server controls from existing controls,
Built-in security through the Windows server or other authentication/authorization methods,
Integration with ADO.NET,
Full support for XML and CSS,
Built-in features for caching frequently requested Web pages on the server.
Navigation sequence of ASP.NET web form
IIS starts the ASP.NET worker process which loads the assembly,
The assembly composes a response to the user,
IIS returns the response to the user in the form of HTML.
ASP.NET Web Form Components
Server controls: Define the user interface of a Web form and built-in features for saving data.
HTML controls: Visual element provided by HTML. They are useful when the more complete feature of server controls is not needed.
Data controls: Data controls connects to SQL and OLE databases and XML data files.
Examples of such controls are SqlConnection, SqlCommand, OleDbConnection, OleDbCommand, DataSet.
System components: Provide access to various system-level events that occur on the server. Ex. EventLog, MessageQueue.
.NET Framework includes
An execution engine called CLR and class library.
Shared (VB.NET) or static members (C#)
Class methods can be used directly without first creating an object from the class. Members can be called from the class name. Example -Math class.
Virtual folder: Web applications can exist only in a location that has been published by IIS as a virtual folder. It is shared resource identified by an alias that represents a physical location on a server. The virtual folder named //localhost is the Web root folder on your computer. IIS determines the physical location of your Web root folder. By default, IIS installs the folder on your boot drive at \Inetpub\wwwroot.
View state: ASP.NET preserves data between requests using view state. View state is available only within the Web form.
State Variable: allows data entered on a Web form available on other Web forms in an application.
Application state variables: Available to all users of an application.
Session state variables: Available only to a single session (user).
Application Event Handlers in ASP.NET
Application_Start:Occurs when first user visits a page.
Application_End:Occurs when no more users of the application.
Application_BeginRequest:Occurs at the beginning of each request to the server.
Application_EndRequest:Occurs at the end of each request to the server.
Session_Start:Occurs when a new user visits a page within your application.
Session_End:Occurs when a user stops requesting pages from the Web application and their session times out.
Session is a unique instance of the browser. Each user can have multiple instances of the browser.
ASP.NET Web Form Events
Page_Init: Here server controls are loaded and initialized.
Page_Load: Server controls are loaded in the Page object.
Page_PreRender: Application is about to render the Page object.
Page_Unload: Page is unloaded from memory.
Page_Disposed: Page object is released from memory.
Page_Error
Unhandled exception occurs
Page_AbortTransaction: Transaction is aborted.
Page_CommitTransaction: Transaction is accepted.
Page_DataBinding: Server control on the page binds to a data source.
Server Control Events in ASP.NET
Postback events: Events cause the Web page to be sent back to the server for immediate processing. Postback events affect performance because they trigger a round-trip to the server.
Cached events: Save controls in the page’s view state to be processed when a postback event occurs.
Validation events: Events occurred before the page is post back to the server.
Application domain: The process space where ASP.NET worker process loads the Web application’s assembly, also called as application domain.
Namespaces organizes code and provide protection from conflicting names called namespace collisions.
Access Modifier for Classes and Modules
Public (VB.NET) or public (C#): Can be accessed by all members in all classes and projects
Friend (VB.NET) or internal(C#): Can be accessed by all members in the current project
Protected (VB.NET) or protected(C#): Can be accessed in the current class and in classes derived from this member’s class
Protected Friend (VB.NET) or protected internal(C#): Can be accessed by all members in the current project and all members in classes derived from this member’s class
Private (VB.NET) or private(C#): Can be accessed by members of the current class only
Inheritance: Base class provides methods, properties, and other members to a derived class.
Abstract classes: Abstract classes defines an interface for derived classes. Abstract classes are declared with the MustInherit (in VB.NET) or abstract (in C#) keyword. Methods and properties are declared as MustOverride (in VB.NET) or as abstract in C#.
Delegates are strong types function pointer used to invoke one or more methods where the actual method invoked is determined at run time.
Interfaces: Similar to abstract classes except interfaces don’t provide any implementation of class members.
Global.asax:The Global object is defined in Global.asax that starts automatically when an application starts. A developer can use events in global object to initialize application-level state variables.
Maintaining State Information: Context.Handler, Query strings, Cookies, View state, Session state, Application state.
Point to be considered for state variables: Maintaining Session state affects performance and should be turned off at the application and page levels when not required.
Application state variables are available throughout the current process, but not across processes. If an application is scaled to run on multiple servers or on multiple processors within a server, each process has its own Application state. The Web application’s boundaries determine the scope of the Application state.
System.Web and System.Web.UI namespaces define most of the objects including Application, Page, Request, and Response objects.
Server Controls vs. HTML Controls
Server controls trigger control events on the server whereas HTML Controls can’t.
Server controls maintains data across requests but with HTML controls data is not maintained.
Server controls is provided with set of properties by .Net framework whereas HTML controls has attributes only.
AutoPostBack: property associated with each control which causes the control to fire postback event. By default, this property is set to False.
ASP.NET List and Table Controls are ListBox, DropDownList, Table, DataGrid, DataList, Repeater.
Validation: The validation controls check the validity of data just before the page is posted back to the server, without a round-trip to the server.
ASP.NET performs control validation on the client side just before posting the Web form back to the server. Once client-side validation succeeds, the Web form is validated again on the server side before the Page_Load event occurs.
To open new window, we can use onclick=”window.open()” attribute. Web application supports client script that runs on the client.
ASP.NET Validation Controls: RequiredFieldValidator, CompareValidator, RangeValidator, RegularExpressionValidator, CustomValidator, ValidationSummary.
To use the validation controls, follow these steps:
Draw a validation control,
Set ControlToValidate or ControltoCompare property,
Set control’s ErrorMessage property,
Set validation control’s text property to show longer error message in a ValidationSummary.
Navigating Between Pages in ASP.NET
Hyperlink control,
Response.Redirect,
Server.Transfer: Only for aspx page, end the currect page and begin executing the new one.
Server.Execute: Begin new one while still displaying the currect one.
Window.Open: Display new browser window.
Layers to data access in ADO.NET
Physical data store: SQL, an OLE, or an Oracle database or an XML file.
Data provider: Connection and command objects that create in-memory representation of data
Data set: In-memory representation of the tables and relationships.
Data view: Presentation of a table in the data set use for filtering or sorting of data.
Types of database connection in ADO.NET: OleDbConnection, SqlConnection, OracleConnection.
Steps to access a database through ADO.NET
Create a connection using a connection object.
Invoke a command to create a DataSet object using an adapter object.
Use the DataSet object in code to display data or to change items in the database.
The database command object provides these three command methods: ExecuteScalar, ExecuteNonQuery, ExecuteReader.
To establish database connection using command object
Create a connection to the database.
Open the connection.
Create a command object containing the SQL command or stored procedure to execute.
Execute the method on the command object.
Close the database connection.
Transactions: Set of database commands that are treated as a single unit.
Commands can be treated as transaction if
Atomic: Each command should perform single unit of work independently.
Consistent: All the relationships between data are maintained correctly.
Isolated: Changes made by other clients can’t affect the current changes.
Durable: Once a change is made, it is permanent.
Transaction processing follows these steps
Begin a transaction,
Process database commands,
Check for errors. If errors occurred, restore the database to its state at the beginning of the transaction,
If no errors occurred, commit the transaction to the database.
IsolationLevel property: The property of transaction objects that handles concurrent changes to a database.
Isolation Level Settings
ReadUncommitted: Does not lock the records being read,
Chaos,
ReadCommitted: Locks the records being read and immediately frees the lock as soon as the records have been read,
RepeatableRead: Locks the records being read and keeps the lock until the transaction completes,
Serializable: Locks the entire data set being read and keeps the lock until the transaction completes.
Exceptions are unusual occurrences in the code of application. Dealing with unusual occurrences is called exception handling. Errors that are not handled are called unhandled exceptions.
Ways to handling exceptions in ASP.NET are
Exception-handling structures,
Error events,
Custom error pages.
Exception-Handling Keywords: Try/try, Catch/catch, Finally/finally, End Try and Throw/throw
Finally/finally: Free resources used within the Try/try section and process any other statements that must run, whether or not an exception has occurred
Exception-Handling Error Events
Page_Error: Resides in the web form,
Global_Error: Resides in the Global.asax file,
Application_Error: Resides in the Global.asax file.
Server Object’s Exception-Handling Events
GetLastError
ClearError
Error pages: Error pages can be .htm or .aspx where users are redirected when unhandled exception occurs.
We can define error page at two level: CustomErrors section of the Web.config file. ErrorPage attribute of the Web form’s @ Page directive.
The customErrors mode attribute must be On to view the error pages. RemoteOnly (the default) means error will be displayed at the client machine and not locally.
The page-level setting supersedes the application-level settings in the Web.config file.
Exception log provides a list of handled exceptions. Use the Throw/throw keyword to intentionally cause an exception.
Tracing records events, a way to record errors by writing error message in the file.
Steps to use tracing in ASP.NET
Turn tracing on.
Write to the trace log.
Read the trace log.
Tracing can be turned on or off for an entire Web application or for an individual page
For an entire application, set the element’s Enabled attribute to True in Web.config file.
For a single page, set the @ Page directive’s Trace attribute to True in the Web form’s HTML.
The Trace object provides the Write and Warn methods.
Messages written with Write are in black, whereas messages written with Warn are in red.
By default, trace output is displayed at the bottom of each Web page, if the element’s PageOutput attribute is set to False in the Web.config file, otherwise written to the Trace.axd file.
By default, you can view Trace.axd only from the local server running the application.
To view the trace log from a remote machine, such as when debugging remotely, set the element’s LocalOnly attribute to False in the Web.config file.
Users can be identified using Cookies. Cookies are small files that a web application can write to the client. Cookies allow interaction with user invisibly. Users can set their browsers not to accept cookies. Approaches when storing and retrieving user information through cookies: Store all the user information as a cookie on the client’s machine. Store an identification key and retrieve user information from a data source using key.
Steps to store cookies in ASP.NET
Check if the client supports cookies by using the Browser object’s Cookies property.
Check if the cookie already exists by using the Request object’s Cookies collection.
Create a new cookie object using the HttpCookie class, if not exist.
Set the cookie object’s Value and Expiration properties.
Add the cookie object to the Response object’s Cookies collection.
Cookie object’s Expires property to Now – to delete Cookies
DllImport attribute to declare unmanaged procedures for use within .NET assemblies.
To hide public .NET members from COM, use the ComVisible attribute.
Mailto protocol to create a message that will be sent from the user’s mail system.
The Mailto protocol is used as part of a hyperlink.
MailMessage and SmtpMail classes to compose and send messages from the server’s mail system.
Authentication is the process of identifying users.
Authorization is the process of granting access to those users based on identity.
Access by Anonymous Users is the way most public Web sites work allows anyone to view info.
ASP.NET Web applications provide anonymous access by impersonation.
Impersonation is the process of assigning a user account to an unknown user.
By default, the anonymous access account is named IUSER_machinename.
Ways to authenticate and authorize users in ASP.NET
Windows authentication: Uses windows user list and privileges to identify and authorize users.
Forms authentication: Directs users to a logon Web form that collects user name and password information, and then authenticates the user against a user list or database that the application maintains.
Passport authentication: Directs new users to a site hosted by Microsoft.
FormsAuthentication class: The FormsAuthentication class is part of the System.Web.Security namespace. Authenticate method of this class checks the user name and password against the user list found in the element of Web.config. RedirectFromLoginPage method of this class displays the application’s start page. Use the FormsAuthentication class to sign out when the user has finished with the application.
Passport authentication identifies users via Microsoft Passport’s single sign-on service. The advantages of Passport authentication are that the user doesn’t have to remember separate user names and passwords for various Web sites
IIS supports ways of encrypting and decrypting Web requests and responses.This cryptography requires that you request an encryption key called a server certificate from an independent third party called a certificate authority. The Secure Sockets Layer (SSL) is the standard means of ensuring that data sent over the Internet can’t be read by others. When a user requests a secure Web page, the server generates an encryption key for the user’s session and then encrypts the page’s data before sending a response. On the client side, the browser uses that same encryption key to decrypt the requested Web page and to encrypt new requests sent from that page.
Steps to be taken before deployment of application
Set the build options: Make the project compatible with an earlier Microsoft .NET. Select the Enable Optimizations check box to make the compiled code smaller, faster, and more efficient. Disable integer overflow checks:Allow classes to be used from the Component Object Model (COM).
Identify the application: To identify your application, open the AssemblyInfo file and enter the application’s Information.
Configure the application: Configuration files are Web.config and Machine.config.
The Machine.config file located in the Windows\Microsoft.NET\Framework\version\config directory. Machine.config sets the base configuration for all .NET assemblies running on the server.
Web.config Attributes: Compilation, CustomErrors, Authentication, Authorization, Trace, SessionState, Globalization.
The global assembly cache (GAC) is a special subfolder within the Windows folder that stores the shared .NET components. When you open the folder, Windows Explorer starts a Windows shell extension called the Assembly Cache Viewer (ShFusion.dll)
You can install strong-named .NET components by dragging them into the Assembly Cache Viewer, or by using the Global Assembly Cache tool (GacUtil.exe).
Monitoring the Server: Windows provides MMC snap-ins for monitoring security, performance, and error events.
Event Viewer snap-in: Lists application, system, and security events on the system.
Performance snap-in: Lets you create new events to display in the Event Viewer.
Tuning Deployed Applications: ProcessModel element’s attributes in the server’s Machine.config file: control the number of threads and the time-out behavior etc. Use the sessionState element’s attributes in the application’s Web.config file: control how Session state information is saved.
ProcessModel Attributes
Maximum number of requests to be queued, How long to wait before checking whether a client is connected, How many threads to allow per processor etc.
Optimization Tips
Turn off debugging for deployed applications.
Avoid round-trips between the client and server.
Turn off Session state if it isn’t needed.
Turn off ViewState for server controls that do not need to retain their values. Use stored procedures with databases.
Use SqlDataReader rather than data sets for read-forward data retrieval.
The ability to add capacity to an application is called scalability. ASP.NET Web applications support this concept through their ability to run in multiple processes and to have those processes distributed across multiple CPUs and/or multiple servers.
A Web application running on a single server that has multiple CPUs is called a Web garden and application running on multiple servers is called a Web farm.
Web Garden Attributes in processModel are
webGarden: Set to “true” to run applications on more than one processor on this server.
cpuMask: Specifies which CPUs should run ASP.NET Web applications.
Multiple Servers
For multiple servers to handle requests for a single HTTP address, you need to install load balancing to your network. Load-balancing services can be provided by hardware or software solutions.
Running a Web application on multiple servers requires that you take special steps to handle Application and Session state information. To share data across multiple sessions in a Web garden or Web farm, you must save and restore the information using a resource that is available to all the processes. This can be done through an XML file, a database, or some other resource using the standard file or database access methods. You can share Session state using: A state server, as specified by a network location. A SQL database, as specified by a SQL connection.
ASP.NET Web applications also have a limited ability to repair themselves through process recycling. Process recycling is the technique of shutting down and restarting an ASP.NET worker process (aspnet_wp.exe) that has become inactive or is consuming excessive resources. You can control how ASP.NET processes are recycled through attributes in the processModel element in the Machine.config file.
Types of Tests
Unit test, Integration test, Regression test, Load test (also called stress test), Platform test.
Web user controls combine one or more server or HTML controls on a Web user control page. User controls create a single visual component that uses several controls. User controls can be used on Web forms throughout a project. User controls are not compiled into assemblies.
Steps to create user control
Add a Web user control page (.ascx) to your project.
Draw the visual interface of the control in the designer.
Write code to create the control’s properties, methods, and events.
Use the control by dragging it from Solution Explorer to the Web form.
Use the control from a Web form’s code by declaring the control at the module level.
Composite custom controls combine one or more server or HTML controls Composite custom compiles to create an assembly (.dll)
Rendered custom controls are created almost entirely from scratch.
Caching: @OutputCache page directive caches a Web form in the server’s memory. OutputCache directive has two required attributes: Duration and VaryByParam. The VaryByParam attribute caches multiple responses from a single Web form. VaryByParam to None caches only one response for the Web form.
XSL Transformations
XSL transformations generate formatted output from an XML input file. XSL positions elements anywhere on the Web form. XSL performs logical operations like repeating and conditional operations. XSL places structured data on a Web form.
Steps to perform an XSL transformation in ASP.NET
Add an XML server control to a Web form.
Set the control’s DocumentSource property to the XML file to format.
Set the TransformSource property to the XSL file to use to format the output.
Creating an XML File
XML files describe structured data in text format. XML identifies data items using … tags. Each item must have a begin tag and an end tag. Item tag names are case sensitive. Attribute values must always be enclosed in double quotation marks. The nested items must be terminated before the containing item is terminated. The XML structure is strictly hierarchical. XML refers to the items in this hierarchy as XML nodes. Nodes have parent-child relationships that are identified using the XPath.
Globalization Approaches in ASP.NET
Create separate web application corresponding to each culture, detect the culture and redirect to appropriate application. Create single web application and adjust output at run time as per culture detected. Create a single Web application that stores culture-dependent strings in resource files that are compiled into satellite assemblies. At run time, detect the user’s culture and load strings from the appropriate assembly.

Articles on Remoting.Net

Remoting.Net Overview
Remote Objects activation
Remoting.Net Channels
Events and Delegates in Remoting Applications
Asynchronous programming in Remoting Applications
Configuring Remoting Applications
Remoting.Net vs Web Services
Remoting.Net Interview Questions
More Interview Questions on Remoting

Also read

One of the important goals of ASP.NET 2.0 is 70% code reduction. The data controls supplied with ASP.NET 2.0 play an important role in making this ambitious goal a reality. Data source controls provide a consistent and extensible method for declaratively accessing data from web pages..............

ASP.NET 2.0 Security Controls

With ASP.NET 2.0, things have changed for the better. For security-related functionalities, ASP.NET 2.0 introduces a wide range of new controls..............

ASP.NET 2.0 New Controls

In addition to the new controls, ASP.NET 2.0 also provides numerous enhancements to existing controls that make these controls more versatile than ever before in building component-based web pages. For example, the Panel control now has a DefaultButton property that specifies which button should be clicked if the user presses the Enter key while the panel has the focus.........

ASP.NET 2.0 Validation Groups

With ASP.NET 2.0, Microsoft introduces a new feature known as validation groups, which enables you to create different groups of validation controls and assign them to input controls, such as text boxes. You can assign a validation group to a collection of input controls if you want to validate the collection of input controls on the same criteria............

ASP.NET 2.0 Themes

One of the neat features of ASP.NET 2.0 is themes, which enable you to define the appearance of a set of controls once and apply the appearance to your entire web application............

ASP.NET 2.0 Web Parts Framework

ASP.NET 2.0 ships with a Web Parts Framework that provides the infrastructure and the building blocks required for creating modular web pages that can be easily customized by the users. You can use Web Parts to create portal pages that aggregate different types of content, such as static text, links, and content that can change at runtime..................

Visual Studio 2005 Improvements

Visual Studio 2005 is the best development tool for building data-driven web applications. As part of the Visual Studio 2005 suite of tools, Microsoft is introducing a new tool called Visual Web Developer (VWD) that is designed to work with the current and next generation of ASP.NET. VWD provides powerful new features for the web developer.................

ASP.NET 2.0 Administration and Management

One of the key goals of ASP.NET 2.0 is to ease the effort required to deploy, manage, and operate ASP.NET web sites. To this end, ASP.NET 2.0 features a new Configuration Management API that enables users to programmatically build programs or scripts that create, read, and update configuration files such as Web.config and machine.config.............