Professional ASP.NET 3.5 in C# and Visual Basic Part 28 pptx

Because of this, when the end user clicks the Login button on the page, ASP.NET recognizes that it should work only with the validation server controls that have the same validation grou

Trang 1

end user clicks a button on the page Listing 4-25 shows an example of separating the validation controls

on a user group page into different buckets

Listing 4-25: Using the ValidationGroup property

<%@ Page Language="VB" %>

<html xmlns="http://www.w3.org/1999/xhtml">

<head runat="server">

<title>Validation Groups</title>

</head>

<body>

<form id="form1" runat="server">

<div>

<h1>St Louis NET User Group</h1>

<p>Username:

<asp:TextBox ID="TextBox1" Runat="server"></asp:TextBox>  Password:

<asp:TextBox ID="TextBox2" Runat="server"

TextMode="Password"></asp:TextBox> 

<asp:Button ID="Button1" Runat="server" Text="Login"

ValidationGroup="Login" />

<br />

<asp:RequiredFieldValidator ID="RequiredFieldValidator1" Runat="server"

Text="* You must submit a username!"

ControlToValidate="TextBox1" ValidationGroup="Login">

</asp:RequiredFieldValidator>

<br />

Text="* You must submit a password!"

ControlToValidate="TextBox2" ValidationGroup="Login">

<p>

Our main meeting is almost always held on the last Monday of the month

Sometimes due to holidays or other extreme circumstances,

we move it to another night but that is very rare Check the home page

of the web site for details The special interest groups meet at other times during the month Check the SIG page and visit their individual sites for more information

You can also check our calendar page for a summary of events.<br />

</p>

<h2>Sign-up for the newsletter!</h2>

<p>Email:

<asp:TextBox ID="TextBox3" Runat="server"></asp:TextBox> 

<asp:Button ID="Button2" Runat="server" Text="Sign-up"

ValidationGroup="Newsletter" /> 

<br />

<asp:RegularExpressionValidator ID="RegularExpressionValidator1"

Runat="server"

Text="* You must submit a correctly formatted email address!"

ControlToValidate="TextBox3" ValidationGroup="Newsletter"

ValidationExpression="\w+([-+.]\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*">

</asp:RegularExpressionValidator>

<br />

Trang 2

Chapter 4: Validation Server Controls

Text="* You forgot your email address!"

ControlToValidate="TextBox3" ValidationGroup="Newsletter">

</p>

</div>

</form>

</body>

</html>

TheValidationGroupproperty on this page is shown in bold You can see that this property takes a

Stringvalue Also note that not only validation controls have this new property The core server

controls also have theValidationGroupproperty because things like button clicks must be associated

with specific validation groups

In this example, each of the buttons has a distinct validation group assignment The first button on the

form usesLoginas a value, and the second button on the form usesNewsletteras a value Then each of the validation controls is associated with one of these validation groups Because of this, when the end

user clicks the Login button on the page, ASP.NET recognizes that it should work only with

the validation server controls that have the same validation group name ASP.NET ignores the validation controls assigned to other validation groups

Using this enhancement, you can now have multiple sets of validation rules that fire only when you want them to fire (see Figure 4-13)

Figure 4-13

225

Trang 3

Another great feature that has been added to validation controls is a property calledSetFocusOnError.

This property takes aBooleanvalue and, if a validation error is thrown when the form is submitted,

the property places the page focus on the form element that receives the error TheSetFocusOnError

property is used in the following example:

Text="* You must submit a username!"

ControlToValidate="TextBox1" ValidationGroup="Login" SetFocusOnError="True">

IfRequiredFieldValidator1throws an error because the end user didn’t place a value inTextBox1, the

page is redrawn with the focus onTextBox1, as shown in Figure 4-14

Figure 4-14

Note that if you have multiple validation controls on your page with theSetFocusOnErrorproperty set to

True, and more than one validation error occurs, the uppermost form element that has a validation error

gets the focus In the previous example, if both the username text box (TextBox1) and the password text

box (TextBox2) have validation errors associated with them, the page focus is assigned to the username

text box because it is the first control on the form with an error

Trang 4

Chapter 4: Validation Server Controls Summar y

Validation controls are a welcome addition for those developers moving from Active Server Pages to

ASP.NET They bring a lot of functionality in a simple-to-use package and, like most things in the NET world, you can easily get them to look and behave exactly as you want them to

Remember that the purpose of having forms in your applications is to collect data, but this data collection has no meaning if the data is not valid This means that you must establish validation rules that can be

implemented in your forms through a series of different controls — the validation server controls

This chapter covered various validation controls in detail, including

❑ RequiredFieldValidator

❑ CompareValidator

❑ RangeValidator

❑ RegularExpressionValidator

❑ CustomValidator

❑ ValidationSummary

In addition to looking at the base validation controls, this chapter also discussed how to apply client-side and server-side validations

227

Trang 5

Wor king with Master Pages

Visual inheritance is a great new enhancement to your Web pages provided by ASP.NET 3.5 This

feature was introduced to ASP.NET in version 2.0 In effect, you can create a single template page

that can be used as a foundation for any number of ASP.NET content pages in your application

These templates, called master pages, increase your productivity by making your applications easier

to build and easier to manage after they are built Visual Studio 2008 includes full designer support

for master pages, making the developer experience richer than ever before This chapter takes a

close look at how to utilize master pages to the fullest extent in your applications and begins by

explaining the advantages of master pages

Why Do You Need Master Pages?

Most Web sites today have common elements used throughout the entire application or on a

major-ity of the pages within the application For instance, if you look at the main page of the Reuters

News Web site (found atwww.reuters.com), you see common elements that are used throughout

the entire Web site These common areas are labeled in Figure 5-1

In this screen shot, notice the header section, the navigation section, and the footer section on the

page In fact, nearly every page within the entire application uses these same elements Even before

master pages, you had ways to put these elements into every page through a variety of means; but

in most cases, doing so posed difficulties

Some developers simply copy and paste the code for these common sections to each and every

page that requires them This works, but it’s rather labor intensive However, if you use the

copy-and-paste method, whenever a change is required to one of these common sections of the

application, you have to go into each and every page and duplicate the change That’s not much fun

and an ineffective use of your time!

In the days of Classic Active Server Pages, one popular option was to put all the common sections

into what was called an include file You could then place this file within your page like this:

Trang 6

Chapter 5: Working with Master Pages

Figure 5-1

The problem with usingincludefiles was that you had to take into account the newly opened HTML

tags in the headerincludefile These tags had to be closed in the main document or in the footerinclude

file It was usually difficult to keep all the HTML tags in order, especially if multiple people worked on

a project Web pages sometimes displayed strange results because of inappropriate or nonexistent tag

closings or openings It was also difficult to work withincludefiles in a visual designer Usinginclude

files didn’t allow the developer to see the entire page as it would appear in a browser The developer

ended up developing the page in sections and hoping that the pieces would come together as planned.

Many hours were wasted ‘‘chasing tables’’ opened in an include file and possibly closed later!

230

Trang 7

With the introduction of ASP.NET 1.0 in 2000, developers started using user controls to encapsulate

common sections of their Web pages For instance, you could build a Web page that included header,

navigation, and footer sections by simply dragging and dropping these sections of code onto each page that required them

This technique worked, but it also raised some issues Before Visual Studio 2005 and ASP.NET 2.0, user controls caused problems similar to those related toincludefiles When you worked in the design view

of your Web page, the common areas of the page displayed only as gray boxes in Visual Studio NET

2002 and 2003 This made it harder to build a page You could not visualize what the page you were

building actually looked like until you compiled and ran the completed page in a browser User controls also suffered from the same problem asincludefiles — you had to match up the opening and closing

of your HTML tags in two separate files Personally, we prefer user controls overincludefiles, but user controls aren’t perfect template pieces for use throughout an application You will find that Visual Studio corrects some of the problems by rendering user-control content in the design view User controls are

ideal if you are including only small sections on a Web page; they are still rather cumbersome, however, when working with larger page templates

In light of the issues withincludefiles and user controls, the ASP.NET team developed the idea of master

pages — an outstanding new way of applying templates to your applications They inverted the way the

developer attacks the problem Master pages live outside the pages you develop, while user controls live

within your pages and are doomed to duplication These master pages draw a more distinct line between the common areas that you carry over from page to page and the content areas that are unique on each page You will find that working with master pages is easy and fun The next section of this chapter looks

at some of the basics of master pages in ASP.NET

The Basics of Master Pages

Master pages are an easy way to provide a template that can be used by any number of ASP.NET pages in your application In working with master pages, you create a master file that is the template referenced by

a subpage or content page Master pages use a.masterfile extension, whereas content pages use the.aspx file extension you’re used to; but content pages are declared as such within the file’sPagedirective

You can place anything you want to be included as part of the template in the.masterfile This can

include the header, navigation, and footer sections used across the Web application The content page

then contains all the page content except for the master page’s elements At runtime, the ASP.NET engine combines these elements into a single page for the end user Figure 5-2 shows a diagram of how this

process works

One of the nice things about working with master pages is that you can visually see the template in the IDE when you are creating the content pages Because you can see the entire page while you are working

on it, it is much easier to develop content pages that use a template While you are working on the content page, all the templated items are shaded gray and are not editable The only items that are alterable are

clearly shown in the template These workable areas, called content areas, originally are defined in the

master page itself Within the master page, you specify the areas of the page that the content pages can use You can have more than one content area in your master page if you want Figure 5-3 shows the

master page with a couple of content areas shown

Trang 8

Figure 5-2

Figure 5-3

232

Trang 9

If you look at the screenshot from Figure 5-3, you can sort of see two defined areas on the page — these are content areas The content area is represented in the design view of the page by a light dotted box

that represents the ContentPlaceHolder control Also, if you hover your mouse over the content area, you will see the name of the control appear above the control (although lightly) This hovering is also shown

in action in Figure 5-3

Companies and organizations will find using master pages ideal, as the technology closely models their typical business requirements Many companies have a common look and feel that they apply across

their intranet They can now provide the divisions of their company with a.masterfile to use when

creating a department’s section of the intranet This process makes it quite easy for the company to keep

a consistent look and feel across its entire intranet

Coding a Master Page

Now look at building the master page shown previously in Figure 5-3 You can create one in any

text-based editor, such as Notepad or Visual Web Developer Express Edition, or you can use the new

Visual Studio 2008 In this chapter, you see how it is done with Visual Studio 2008

Master pages are added to your projects in the same way as regular.aspxpages — choose the Master

Page option when you add a new file to your application, as shown in Figure 5-4

Figure 5-4

Because it’s quite similar to any other.aspxpage, the Add New Item dialog enables you to choose from

a master page using the inline coding model or a master page that places its code in a separate file Not placing your server code in a separate file means that you use the inline code model for the page you are creating This option creates a single.masterpage Choosing the option to place your code in a separate file means that you use the new code-behind model with the page you are creating Selecting the check box ‘‘Place code in separate file’’ creates a single.masterpage, along with an associated.master.vbor

Trang 10

.master.csfile You also have the option of nesting your master page within another master page by

selecting the Select master page option, but this is covered later in this chapter

A sample master page that uses the inline-coding model is shown in Listing 5-1

Listing 5-1: A sample master page

<%@ Master Language="VB" %>

<script runat="server">

</script>

<html xmlns="http://www.w3.org/1999/xhtml" >

<head runat="server">

<title>My Company Master Page</title>

<asp:ContentPlaceHolder id="head" runat="server">

</asp:ContentPlaceHolder>

</head>

<body>

<form id="form1" runat="server">

<table cellpadding="3" border="1">

<tr bgcolor="silver">

<td colspan="2">

<h1>My Company Home Page</h1>

</td>

</tr>

<tr>

<td>

<asp:ContentPlaceHolder ID="ContentPlaceHolder1"

runat="server">

</td>

<td>

<asp:ContentPlaceHolder ID="ContentPlaceHolder2"

runat="server">

</td>

</tr>

<tr>

<td colspan="2">

</td>

</tr>

</table>

</form>

</body>

</html>

This is a simple master page The great thing about creating master pages in Visual Studio 2008 is that

you can work with the master page in code view, but you can also switch over to design view to create

your master pages just as any other ASP.NET page

234

Định dạng
Số trang	10
Dung lượng	504,46 KB