Input Validation in ASP.NET

Input Validation in ASP.NET

• Input validation ensures user input is correct and accurate before it's processed in ASP.NET.
• Performed on both the client and server sides to ensure data integrity and security.

Client-Side Validation

• Occurs in the user's browser before a form is submitted to the server.
• Advantages include reduced server load, faster user feedback, and improved user experience.
• Disadvantages: can be bypassed by disabling JavaScript, and is not secure for sensitive data.

Server-Side Validation

• Occurs on the server after the form is submitted.
• Advantages include better security, inability to bypass, and suitability for complex validation.
• Disadvantages: slower due to server round trips, and increases server load.

Validation Controls in ASP.NET

• ASP.NET offers a variety of validation controls for validating user input in web forms.
• Common validation controls include RequiredFieldValidator, CompareValidator, RangeValidator, RegularExpressionValidator, and ValidationSummary.

RequiredFieldValidator

• Ensures a field isn't left empty.
• Usable for text boxes, dropdown lists, checkboxes and other input options.

CompareValidator

• Compares the value of one input control to another for password validation or other scenarios.

RangeValidator

• Checks if a value falls within a specific range.
• Applicable for validating age, income, or date of birth inputs.

RegularExpressionValidator

• Validates user input against a specified regular expression pattern.
• Enforces formats for email addresses, phone numbers and postal codes

ValidationSummary

• Displays a report of all validation errors on a web page.

Important points for validation controls

• ControlToValidate property is a must for all validate controls
• Only one input control is validated by one validation control, however, an input control may have several validation controls attached
• To enable any validation control, specific code needs to be added to the web.config file.

ASP.NET RequiredFieldValidation Control

• Verifies data has been entered into for the input control
• A RequiredFieldValidator control can be used for each form element users want to enforce as mandatory.
• Properties include ControlToValidate and ErrorMessage.

ASP.NET CompareValidator Control

• Compares data entered between an input control with either a specific value or a another control value.
• Useful when the data entered by user is always case-sensitive.
• It has properties such as ControlToValidate, ControlToCompare, and ErrorMessage.

ASP.NET RangeValidator Control

• Verifies if a control value is within a valid range
• Important attributes include MaximumValue, MinimumValue, and values Type

RegularExpressionValidator

• Validates user input matches a specific regular expression
• Useful for enforcing valid email addresses, phone numbers, and postal codes.
• Has key properties such as ControlToValidate, ValidationExpression, and ErrorMessage

AdRotator Control

• Randomly selects banner graphics from a list specified in an external XML schedule file known as the advertisement file.
• It can specify both the advertisement file and the type of window the link should follow using the AdvertisementFile and Target properties, respectively.
• Code: <asp:AdRotator runat = "server" AdvertisementFile = "adfile.xml" Target = "_blank" />

Advertisement File

• It is an XML file with data that displays the advertisements.
• Extensible Markup Language (XML) is a W3C standard for text document markup and enables storing data in a structured format using meaningful tags.
• XML is not a language, but a set of rules for creating markup languages, which facilitates developers to create custom tag sets

Common XML Elements

• Advertisements: Encloses the advertisement file.
• Ad: Delineates each separate advertisement.
• ImageUrl: Path to the image that will show.
• NavigateUrl: The link when a user clicks the ad.
• AlternateText: The text displayed if the image can't be shown.
• Keyword: Keyword identifies a group of ads to be used in filtering.
• Impressions: The number indicating how often an ad will appear.
• Height: Height of the image to be displayed.
• Width: Width of the image to be displayed.

Calendar Control

• A functionally rich web control with a range of capabilities:
• Displays one month at a time.
• Allows users to select a day, week, or month.
• Supports selecting a range of days.
• Enables moving between months.
• The display of days can be programmatically controlled

Calendar Control Syntax

• The basic syntax looks as follows: <asp:Calender ID = "Calendar1" runat = "server"> </asp:Calender>

Properties

• Caption: Sets the caption for the calendar control
• CaptionAlign: Sets the alignment for the caption
• CellPadding: Sets spaces between data and cell border.
• CellSpacing: Sets space between cells.
• DayHeaderStyle: Style properties for the day-of-the-week section.
• DayNameFormat: Sets the format of days of the week.
• DayStyle: Sets the style properties for days in the displayed month.
• FirstDayOfWeek: Sets the day of the week to display in the first column.
• NextMonthText: Sets text for the next month navigation control, defaulting to >.
• NextPrevFormat: Sets the format of the next and previous month navigation control.
• OtherMonthDayStyle: Sets the style properties for days not displayed in the current month
• PrevMonthText: Sets default text for the previous month navigation control, default is <
• SelectedDate: Gets or sets the selected date
• SelectedDates: Gets a collection of DateTime objects showing the selected dates
• SelectedDayStyle: Gets the style attributes to apply for the selected dates
• SelectionMode: Defines what the user can select, such as a single day, week, or an entire month
• SelectMonthText: Gets or sets the text within the month selection element in the selector column
• SelectorStyle: Gets the style attributes for the week and month selector column
• SelectWeekText: Gets or sets the displayed text for the week selection element, the selector column
• ShowDayHeader: Decides if the day headings get displayed
• ShowGridLines: Sets whether to show gridlines
• ShowNextPrevMonth: Gets whether to show next and previous month
• ShowTitle: Gets whether the title section will display
• TitleFormat: Format for the title section.
• TitleStyle: Defines the style properties for the calendar control's title heading.
• TodayDayStyle: Sets style properties for today's date in particular.
• TodaysDate: Gets or sets a value for the current days date
• VisibleDate: Gets or sets the date value which specifies what month to display first
• WeekendDayStyle: Sets the style properties for weekend dates

Calendar Events

• SelectionChanged: Occurs when a day, week, or month is selected
• DayRender: Occurs when each data cell of the calendar control is rendered
• VisibleMonthChanged: Occurs when a user changes a month

Setting Selection Mode

• Calendar controls can allow users to select a single day, week, or month.
• Achieved via the SelectionMode property.
• Possible values are Day, DayWeek, DayWeekMonth, or None

State Management

• The technique uses that maintains and stores the state of the page/application until the user’s session ends.
• When an error occurs in the form the user does not have to keep re-entering the info

ASP.Net State Management Techniques

• There are 2 ways to control the state of an application in ASP.NET:
• Client Side State Management
• Server Side State Management

Client Side State Management

• Data added by the user, or info about their interaction with the server, stores on the client's machine/page.
• Server resources aren't used during the process.
• Methods include:
  • View State
  • Cookies
  • Hidden Fields
  • Query String

View State

• Used to maintain state at the page level which means that the info stays for a specific single page
• Data in View State gets lost once the user navigates somewhere else from the page
• It is the default method to store information about controls on a page.
• Useful when a user redirects back to the first page and the info added persists until he leaves the page

Cookies

• Small text files stored on the client's computer to uniquely id users
• When you say cookie this small file is generated and stored on the client side to keep personal info on the user
• When a user requests a page, the server creates one cookie and sends to the user

Types of Cookies

• Persistence Cookies - Cookies w/an expiry date/time, stores on the user's machine
• Non-Persistence Cookies - Not stored on the user's machine; only stay as long as the user remains on the same browser - wiped when the browser closes

Query String

• Data is passed in the URL as key-value pairs.
• Mainly to fetch data from one page to another, passing values while redirecting
• Anyone can see value of the query string since they are in URL
• Request.QueryString() is used to retrieve a query string value.

HiddenField

• A non-visual ASP.NET control used to store values on the client side.
• Type of client-side state management, stores values between postbacks
• Data is not encrypted or shielded.
• Used in ASP.NET for ViewState management

Server Side State Management

• A method of state management that stores user-specific information or current application state on the web server.
• It makes full use of the servers memory capacity
• Types include:
  • Session State
  • Application State

Session State

• Session can store values on the Server which makes it a state management technique
• Effective preservation of data across separate different sessions of the user.
• Session stores and identifies a user by assigning each of them a unique Session ID.
• The ASP.NET web server generates Session ID that tracks each individual person
• Session is one of the better ways to control client state since data stores for all users separately and very securely

Setting Session Timeout

• ASP.NET web apps defaults for setting the session to 20 minutes and wipes data and destroys after time
• Otherwise, you can manually set the session timeout by editing the web.config file with the following code to your value: <sessionState timeout="1"> </sessionState>
• Here 1 means 1 minute

Application State

• An ASP.NET server-side application manages the technique.
• The data is stored in Application State which means it is common to all and can be accessed any time or place from the app
• Differs from session state as that one is specific to a user session, while the Application State is made common for every user.