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BETA MATERIALS FOR MICROSOFT CERTIFIED TRAINER PREPARATION PURPOSES ONLY Module 2: Using Web Controls 17 Demonstration: Linking Two Controls Together Topic Objective To introduce the demonstration Lead-in In this demonstration, you will see how to bind a Label control to a list box Delivery Tip In this demonstration, you will see how to bind a Label control to a list box Open the page you created in the last demo, intrinsic.aspx Add a label control to the page Bind the label control to the listbox by setting its Text attribute to: " " Create a Page_Load event and call Page.DataBind() Save and test The completed code for this demonstration is in the binding.aspx page BETA MATERIALS FOR MICROSOFT CERTIFIED TRAINER PREPARATION PURPOSES ONLY 18 Module 2: Using Web Controls $ Using Input Validation Controls Topic Objective To introduce the topics in this section Lead-in Validating user input is a common scenario in a Webbased application For production applications, developers often end up spending a lot of time coding for validation tasks ! Input Validation Controls ! Adding Input Validation Controls to a Form ! Validating an Entire Page ! Demonstration: Adding Input Validation Controls ! Advantages of Using Input Validation Controls In HTML 3.2, validating data is a difficult process Validation code can be run either on the client or on the server, or both Each time you recieve a request, you not only need to write code that checks the input, you need to write error messages to help the user to correctly fill in the form This is a taxing process for end users, developers, and servers With the introduction of input validation controls in ASP.NET, the task of validating input is easier than it has been in the past In this section, you will learn about the advantages of using input validation controls You will also learn how to add these controls to an ASP.NET page BETA MATERIALS FOR MICROSOFT CERTIFIED TRAINER PREPARATION PURPOSES ONLY Module 2: Using Web Controls 19 Input Validation Controls Topic Objective To list the input validation controls available in ASP.NET Lead-in There are five validation controls that ship with ASP.NET ! RequiredFieldValidator ! CompareValidator ! RangeValidator ! RegularExpressionValidator ! CustomValidator Validation controls are added to an ASP.NET page like other server controls There are controls for specific types of validation, such as range checking or pattern matching, plus a RequiredFieldValidator control that ensures a user does not skip an entry field The validation controls have both uplevel and downlevel client support Uplevel browsers perform validation on the client (using JavaScript and DHTML) Client-side validation enhances the validation scheme by checking user input as the user enters data This allows errors to be detected on the client before the form is submitted, preventing the round-trip necessary for server-side validation In uplevel checking, if there is an error in user input, a trip is not made to the server; instead the associated error messages are shown on the client Downlevel browsers perform validation on the server Both scenarios use the same programming model Note More than one input control can be associated with a web control For example, there can be a required and compare validator for the same text box web control Also, the validation controls also work with html web controls BETA MATERIALS FOR MICROSOFT CERTIFIED TRAINER PREPARATION PURPOSES ONLY 20 Module 2: Using Web Controls The following table lists the validation controls included in the ASP.NET Framework Validation control Function RequiredFieldValidator Checks whether value has been entered into a control CompareValidator Compares an input control to a fixed value or another input control It can be used for password verification fields, for example It is also possible to typed date and number comparisons RangeValidator Much like CompareValidator, but can check that the input is between two values or the values of other input controls RegularExpressionValidator Checks that the entry matches a pattern defined by a regular expression This type of validation allows you to check for predictable sequences of characters, such as those in social security numbers, e-mail addresses, telephone numbers, postal codes, and so on CustomValidator This allows you to write your own code to take part in the validation framework ValidationSummary Collects all validation errors and places them in a list within the page For more information about using the Input Validation controls, see the NET Framework SDK documentation BETA MATERIALS FOR MICROSOFT CERTIFIED TRAINER PREPARATION PURPOSES ONLY Module 2: Using Web Controls 21 Adding Input Validation Controls to a Form Topic Objective To explain how to use input validation controls on an ASP.NET page Lead-in Let’s look at how these validation controls are added to a page ! Properties: # ControlToValidate # ErrorMessage # Display The standard code used to add input validation controls to a form is as follows: In the above code, controlToValidate is the id of the control whose input is being validated (a text box, in most cases) The errorMessage property is the error message that is displayed if the input is not valid, and the display property indicates how the validation control will be rendered in the page If you set the display property to static implies that each validation control takes up space even when no error message text is visible, allowing you to define a fixed layout for the page Validation controls cannot occupy the same space on the page, so you must give them each separate locations on the page Setting the display property to dynamic means that the layout of the page changes, sometimes causing controls to jump around In addition to the above-mentioned required properties, each validation control has more specific properties that define how the control should behave The following examples show how to add validation controls BETA MATERIALS FOR MICROSOFT CERTIFIED TRAINER PREPARATION PURPOSES ONLY 22 Module 2: Using Web Controls RequiredFieldValidator control Use the RequiredFieldValidator control to require input in a field The following code shows how to use the RequiredFieldValidator control RangeValidator control To test whether an input value falls within a given range, use the RangeValidator control The RangeValidator control uses two additional properties to perform its validation–MinimumControl and MaximumControl These properties define the minimum and maximum values of the valid range Important In the beta version of Visual Studio.NET, the MinimumControl and MaximumControl properties will be replaced by MinimumValue and MaximumValue In the following example, the txtAge field must have a value between 18 and 50 If the value does not fall within the range, an error message is displayed and no trip to the server occurs CompareValidator control To use one control to test the validity of a second control, or to test input against a specific value, use the CompareValidator control The CompareValidator control uses the following additional properties to perform its validation: ! ValueToCompare or ControlToCompare Set ValueToCompare to compare to a constant value Set ControlToCompare to the ID of another control to compare against If you set both ValueToCompare and ControlToCompare, ControlToCompare takes precedence BETA MATERIALS FOR MICROSOFT CERTIFIED TRAINER PREPARATION PURPOSES ONLY Module 2: Using Web Controls ! 23 Type The data type of the two values to be compared ! Operator The comparison to use Operators are specified with the name of the comparison operators, such as Equal, NotEqual, GreaterThan, GreaterThanEqual, and so on The following shows an example in the aspx file of a Web Form Textbox control with required field validation A table is used to control layout In the following example, the txtAge field must have a value greater than or equal to zero BETA MATERIALS FOR MICROSOFT CERTIFIED TRAINER PREPARATION PURPOSES ONLY 24 Module 2: Using Web Controls Validating an Entire Page Topic Objective To introduce the mechanisms available to determine if all controls on a page are valid Lead-in Sometimes you need to know if all the controls on a page are valid before performing some other action ! Page.IsValid property Sub Submit_click (s A Object, Sub Submit_click (s A Object, If Page.IsValid Then If Page.IsValid Then Message.Text = "Page is Message.Text = "Page is End If End If End Sub End Sub ! e As EventArgs) e As EventArgs) valid!" valid!" ValidationSummary control Sometimes you need to know if all the controls on a page are valid before performing some other action In fact, in client side validation, values are sent across to the server only when all controls are valid IsValid Property ASP.NET developers can check the Page.IsValid property at runtime to determine whether all validation server controls on a page are currently valid This provides a simple “one line” way to determine whether to proceed with business logic Sub Submit_click (s A Object, e As EventArgs) If Page.IsValid Then Message.Text = "Page is valid!" End If End Sub BETA MATERIALS FOR MICROSOFT CERTIFIED TRAINER PREPARATION PURPOSES ONLY Module 2: Using Web Controls 25 Validation Summary Control If a validation control is in error, an error message may be displayed in the page by the validation control or in a ValidationSummary control elsewhere on the page The ValidationSummary control is displayed when the IsValid property of the page is false It “polls” each of the validation controls on the page and aggregates the text messages exposed by each ! The ValidationSummary updates itself without posting back if it detects errors ! The ValidationSummary can optionally display a message box to the user if there are errors BETA MATERIALS FOR MICROSOFT CERTIFIED TRAINER PREPARATION PURPOSES ONLY 26 Module 2: Using Web Controls Demonstration: Adding Input Validation Controls Topic Objective To demonstrate using input validation controls on an ASP.NET page Lead-in In this demonstration, you will see how to add input validation controls to a form In this demonstration, you will see how to add input validation controls to text controls on a form Delivery Tip Open the page you created in the last demo intrinsic.aspx Add a RequiredField validator to the txtName text box See the file validation.aspx for an example Save and test the page Show the error message displayed when the Save button is clicked while the text box is blank View the source of the page to show that the control generated client-side code Open the page validate_all.aspx Show all the validation controls used Test the page Show how the Validation Summary control works and the Page.IsValid test in the click event procedure BETA MATERIALS FOR MICROSOFT CERTIFIED TRAINER PREPARATION PURPOSES ONLY Module 2: Using Web Controls 27 Advantages of Using Input Validation Controls Topic Objective To describe the advantages of using the input validation controls in the ASP.NET framework ! ! Uses DHTML and JScript library to write client logic ! In HTML, validating data is a difficult process DTHML and scripting languages improve things somewhat However, coding for validating user input is still a time-consuming process for developers Create client-side and server-side validation ! Lead-in Provide immediate feedback to the user Allow enhancement of client-side validation and behavior Most Web sites perform their validation checks on the server However, most applications also need client-side validation checks The process of writing two versions of validation code can be extremely time consuming for developers Validation controls eliminate this problem because almost of the duplicated logic is encapsulated in the controls Validation controls check controls for a specific type of error condition and display a description of that problem In addition the controls create browser-specific code So if a client with Internet Explorer 4.0 or later uses the page, it can perform the same input validation that takes place on the server without client script Using validation controls has the following advantages: ! Provides immediate feedback to the user Immediate feedback is given to the user on whether the data entered is valid or not The error messages appear and disappear immediately after the bad input is entered/corrected ! Creates client-side and server-side validation If the browser supports client-side script, the controls error checking before posting the data to the server This saves the user time and reduces hits on the server ! Uses DHTML and JScript library to write client logicThe client logic is contained in a JScript library, so no ActiveX components or Java applets are used ! Allows enhancement of client-side validation and behavior An object model is exposed on the client to allow enhancement of clientside validation and behavior BETA MATERIALS FOR MICROSOFT CERTIFIED TRAINER PREPARATION PURPOSES ONLY 28 Module 2: Using Web Controls Selecting Controls for Applications Topic Objective To describe appropriate situation for using different types of controls Use Web controls when: # Lead-in When creating Web Forms, you can use different classes of controls You prefer a Visual Basic-like programming model # You need specific functionality such as a calendar or ad rotator # You prefer an HTMLlike object model # You are working with existing HTML pages and want to quickly add Web Forms functionality You are writing a page that might be used by a variety of browsers # Use HTML controls when: # The control will interact with client and server script When creating ASP.NET pages, you can use different classes of controls You can mix control types on the same page For example, your ASP.NET page might include a form made up of Web controls plus an HTML control converted from an HTML element The following table summarizes some of the situations in which you would decide to use a particular control Type of control Use it when Web control You prefer a Visual Basic-like programming model You are writing a Web Forms page that might be viewed by a variety of browsers You need specific functionality such as a calendar or ad rotator that is available only as a Web Forms control You are creating applications with nested controls and want to be able to catch events at the container level HTML control You prefer an HTML-like object model You are working with existing HTML pages and want to quickly add Web Forms functionality Because HTML controls map exactly to HTML elements, any HTML design environment can support them The control will also interact with client and server script As a general rule, Web controls are more capable and have a richer object model than HTML controls If you are writing your ASP.NET page so that all processing occurs on the server, Web controls are a good choice BETA MATERIALS FOR MICROSOFT CERTIFIED TRAINER PREPARATION PURPOSES ONLY Module 2: Using Web Controls 29 Lab 2: Creating a Form that Performs Validation Topic Objective To introduce the lab Lead-in In this lab, you will create a form that uses validation controls to validate user input BETA MATERIALS FOR MICROSOFT CERTIFIED TRAINER PREPARATION PURPOSES ONLY 30 Module 2: Using Web Controls Review Topic Objective To reinforce module objectives by reviewing key points ! ! Validate user input on an ASP.NET page using input validation controls ! The review questions cover some of the key concepts taught in the module Use properties, methods, and events of Web controls ! Lead-in Add Web controls to an ASP.NET page Bind two controls together What is the prefix tag that you must use to create Web controls? asp: List the input validation controls included with ASP.NET RangeValidator, RequiredFieldValidator, CompareValidator, RegularExpressionValidator, CustomValidator How you create an event procedure for a button? Set up the event procedure in the button’s tag by setting the onclick property, then write the event procedure in a section BETA MATERIALS FOR MICROSOFT CERTIFIED TRAINER PREPARATION PURPOSES ONLY ... PURPOSES ONLY iv Module 2: Using Web Controls Module Strategy Use the following strategy to present this module: ! What Are Web Controls? Web controls are just a category of server controls Everything... PURPOSES ONLY Module 2: Using Web Controls What Are Web Controls? Topic Objective To remind students of the difference between Web controls and HTML controls and list the categories of Web controls. .. databases using list-bound controls in Module ? ?Using ADO.NET to Access Data.” BETA MATERIALS FOR MICROSOFT CERTIFIED TRAINER PREPARATION PURPOSES ONLY Module 2: Using Web Controls Web controls