Professional ASP.NET 3.5 in C# and Visual Basic Part 29 pps

This control defines the areas of the template where the content page can place its content: In the case of this master page, two defined areas exist where the content page can

Start by reviewing the code for the master page The first line is the directive:

<%@ Master Language="VB" %>

Instead of using thePagedirective, as you would with a typical.aspxpage, you use theMasterdirective for a master page This master page uses only a single attribute,Language TheLanguageattribute’s value here isVB, but of course, you can also useC#if you are building a C# master page

You code the rest of the master page just as you would any other.aspxpage You can use server controls, raw HTML and text, images, events, or anything else you normally would use for any.aspxpage This means that your master page can have aPage_Loadevent as well or any other event that you deem

appropriate

In the code shown in Listing 5-1, notice the use of a new server control — the<asp:ContentPlaceHolder>

control This control defines the areas of the template where the content page can place its content:

<tr>

<td>

<asp:ContentPlaceHolder ID="ContentPlaceHolder1"

runat="server">

</asp:ContentPlaceHolder>

</td>

<td>

<asp:ContentPlaceHolder ID="ContentPlaceHolder2"

runat="server">

</asp:ContentPlaceHolder>

</td>

</tr>

In the case of this master page, two defined areas exist where the content page can place content Our

master page contains a header and a footer area It also defines two areas in the page where any inheriting content page can place its own content Look at how a content page uses this master page

Coding a Content Page

Now that you have a master page in place in your application, you can use this new template for any

content pages in your application Right-click the application in the Solution Explorer and choose Add

New Item to create a new content page within your application

To create a content page or a page that uses this master page as its template, you select a typical Web

Form from the list of options in the Add New Item dialog (see Figure 5-5) Instead of creating a typical

Web Form, however, you check the Select Master Page check box This gives you the option of associating this Web Form later to some master page

After you name your content page and click the Add button in the Add New Item dialog, you are

pre-sented with the Select a Master Page dialog, as shown in Figure 5-6

This dialog allows you to choose the master page from which you want to build your content page You choose from the available master pages that are contained within your application For this example,

select the new master page that you created in Listing 5-1 and click OK This creates the content page

The created page is a simple.aspxpage with only a couple of lines of code contained in the file, as shown

in Listing 5-2

Figure 5-5

Figure 5-6

Listing 5-2: The created content page

<%@ Page Language="VB" MasterPageFile="~/Wrox.master" Title="Untitled Page" %>

<script runat="server">

</script>

<asp:Content ID="Content1" ContentPlaceHolderID="head" Runat="Server">

</asp:Content>

<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1"

Runat="Server">

</asp:Content>

This content page is not much different from the typical.aspxpage you coded in the past The big

difference is the inclusion of theMasterPageFileattribute within thePagedirective The use of this

attribute indicates that this particular.aspxpage constructs its control’s based on another page The

location of the master page within the application is specified as the value of theMasterPageFile

attribute

The other big difference is that it contains neither the<form id="form1" runat="server">tag nor any opening or closing HTML tags that would normally be included in a typical.aspxpage

This content page may seem simple, but if you switch to the design view within Visual Studio 2008, you see the power of using content pages What you get with visual inheritance is shown in Figure 5-7

Figure 5-7

In this screenshot, you can see that just by using theMasterPageFileattribute in thePagedirective, you

are able to visually inherit everything that theWrox.masterfile exposes From the design view within

Visual Studio, you can also see what master page you are working with as the name of the referenced

master page is presented in the upper-right corner of the Design view page If you try and click into the

gray area that represents what is inherited from the master page, you will see that your cursor changes

to show you are not allowed This is illustrated in Figure 5-8 (the cursor is on the word Page in the title)

Figure 5-8

All the common areas defined in the master page are shown in gray, whereas the content areas that you

specified in the master page using the<asp:ContentPlaceHolder>server control are shown clearly and

available for additional content in the content page You can add any content to these defined content

areas as if you were working with a regular.aspxpage An example of using this.masterpage for a

content page is shown in Listing 5-3

Listing 5-3: The content page that uses Wrox.master

VB

<%@ Page Language="VB" MasterPageFile="~/Wrox.master" %>

<script runat="server">

Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs)

Label1.Text = "Hello " & TextBox1.Text & "!"

End Sub

</script>

<asp:Content ID="Content1" ContentPlaceHolderId="ContentPlaceHolder1"

runat="server">

<b>Enter your name:</b><br />

<asp:Textbox ID="TextBox1" runat="server" />

<br />

<br />

<asp:Button ID="Button1" runat="server" Text="Submit"

OnClick="Button1_Click" /><br />

<br />

<asp:Label ID="Label1" runat="server" Font-Bold="True" />

</asp:Content>

<asp:Content ID="Content2" ContentPlaceHolderId="ContentPlaceHolder2"

runat="server">

<asp:Image ID="Image1" runat="server" ImageUrl="wrox.gif" />

</asp:Content>

C#

<%@ Page Language="C#" MasterPageFile="~/Wrox.master" %>

<script runat="server">

protected void Button1_Click(object sender, System.EventArgs e)

{

Label1.Text = "Hello " + TextBox1.Text + "!";

}

</script>

Right away you see some differences As stated before, this page has no <form id="form1"

runat="server">tag nor any opening or closing<html>tags These tags are not included because they are located in the master page Also notice a new server control — the<asp:Content>server control

<asp:Content ID="Content1" ContentPlaceHolderId="ContentPlaceHolder1"

runat="server">

</asp:Content>

The<asp:Content>server control is a defined content area that maps to a specific<asp:ContentPlace

Holder>server control on the master page In this example, you can see that the<asp:Content>server control maps itself to the<asp:ContentPlaceHolder>server control in the master page that has theID

ofContentPlaceHolder1 Within the content page, you don’t have to worry about specifying the location

of the content because this is already defined within the master page Therefore, your only concern is to place the appropriate content within the provided content sections, allowing the master page to do most

of the work for you

Just as when you work with any typical.aspxpage, you can create any event handlers for your content page In this case, you are using just a single event handler — the button click when the end user submits the form The created.aspxpage that includes the master page and content page material is shown in

Figure 5-9

Figure 5-9

Mixing Page Types and Languages

One interesting point: When you use master pages, you are not tying yourself to a specific coding model (inline or code-behind), nor are you tying yourself to the use of a specific language You can feel free to mix these elements within your application because they all work well

You could use the master page created earlier, knowing that it was created using the inline-coding model,

and then build your content pages using the code-behind model Listing 5-4 shows a content page created

using a Web Form that uses the code-behind option

Listing 5-4: A content page that uses the code-behind model

.aspx (VB)

<%@ Page Language="VB" MasterPageFile="~/Wrox.master" AutoEventWireup="false"

CodeFile="MyContentPage.aspx.vb" Inherits="MyContentPage" %>

<asp:Content ID="Content1" ContentPlaceHolderID="head" Runat="Server">

</asp:Content>

<asp:Content ID="Content2" ContentPlaceHolderId="ContentPlaceHolder1"

runat="server">

<b>Enter your name:</b><br />

<asp:Textbox ID="TextBox1" runat="server" />

<br />

<br />

<asp:Button ID="Button1" runat="server" Text="Submit" /><br />

<br />

<asp:Label ID="Label1" runat="server" Font-Bold="True" />

</asp:Content>

<asp:Content ID="Content3" ContentPlaceHolderId="ContentPlaceHolder2"

runat="server">

<asp:Image ID="Image1" runat="server" ImageUrl="ineta.JPG" />

</asp:Content>

VB Code-Behind

Partial Class MyContentPage

Inherits System.Web.UI.Page

Protected Sub Button1_Click(ByVal sender As Object, _

ByVal e As System.EventArgs) Handles Button1.Click

Label1.Text = "Hello " & TextBox1.Text & "!"

End Sub

End Class

C# Code-Behind

public partial class MyContentPage : System.Web.UI.Page

{

protected void Button1_Click (object sender, System.EventArgs e)

{

Label1.Text = "Hello " + TextBox1.Text + "!";

}

}

Even though the master page is using the inline-coding model, you can easily create content pages (such

as the page shown in Listing 5-4) that use the code-behind model The pages will still work perfectly

Not only can you mix the coding models when using master pages, you can also mix the

program-ming languages you use for the master or content pages Just because you build a master page in C#

doesn’t mean that you are required to use C# for all the content pages that use this master page You

can also build content pages in Visual Basic For a good example, create a master page in C# that uses

thePage_Loadevent handler and then create a content page in Visual Basic Once it is complete, run the page It works perfectly well This means that even though you might have a master page in one of the available NET languages, the programming teams that build applications from the master page can use whatever NET language they want You have to love the openness that the NET Framework˜offers!

Specifying Which Master Page to Use

You just observed that it is pretty easy to specify at page level which master page to use In thePage

directive of the content page, you simply use theMasterPageFileattribute:

<%@ Page Language="VB" MasterPageFile="~/Wrox.master" %>

Besides specifying the master page that you want to use at the page level, you have a second way to

specify which master page you want to use in theweb.configfile of the application This is shown in

Listing 5-5

Listing 5-5: Specifying the master page in the web.config file

<configuration>

<system.web>

<pages masterPageFile="~/Wrox.master" />

</system.web>

</configuration>

Specifying the master page in theweb.configfile causes every single content page you create in the

application to inherit from the specified master page If you declare your master page in theweb.config

file, you can create any number of content pages that use this master page Once specified in this manner, the content page’sPagedirective can then be constructed in the following manner:

<%@ Page Language="VB" %>

You can easily override the application-wide master page specification by simply declaring a different

master page within your content page:

<%@ Page Language="VB" MasterPageFile="~/MyOtherCompany.master" %>

By specifying the master page in theweb.config, you are really not saying that you want all the.aspx

pages to use this master page If you create a normal Web Form and run it, ASP.NET will know that

the page is not a content page and will run the page as a normal.aspxpage

If you want to apply the master page template to only a specific subset of pages (such as pages contained within a specific folder of your application), you can use the<location>element within theweb.config

file, as illustrated in Listing 5-6

Listing 5-6: Specifying the master page for a specific folder in the web.config file

<configuration>

<location path="AdministrationArea">

<system.web>

<pages masterPageFile="~/WroxAdmin.master" />

</system.web>

</location>

</configuration>

With the addition of this<location>section in theweb.configfile, you have now specified that a

specific folder (AdministrationArea) will use a different master file template This is done using the path

attribute of the<location>element The value of thepathattribute can be a folder name as shown, or

it can even be a specific page — such asAdminPage.aspx

Working with the Page Title

When you create content pages in your application, by default all the content pages automatically use

the title that is declared in the master page For instance, you have primarily been using a master page

with the titleMy Company Master Page Every content page that is created using this particular master

page also uses the sameMy Company Master Pagetitle You can avoid this by specifying the page’s title

using theTitleattribute in the@Pagedirective in the content page You can also work with the page title

programmatically in your content pages To accomplish this, in the code of the content page, you use the

Masterobject TheMasterobject conveniently has a property calledTitle The value of this property is

the page title that is used for the content page You code it as shown in Listing 5-7

Listing 5-7: Coding a custom page title for the content page

VB

<%@ Page Language="VB" MasterPageFile="~/Wrox.master" %>

<script runat="server">

Protected Sub Page_LoadComplete(ByVal sender As Object, _

ByVal e As System.EventArgs)

Master.Page.Title = "This page was generated on: " & _ DateTime.Now.ToString()

End Sub

</script>

C#

<%@ Page Language="C#" MasterPageFile="~/wrox.master" %>

<script runat="server">

protected void Page_LoadComplete(object sender, EventArgs e)

{

Master.Page.Title = "This page was generated on: " +

}

</script>

Working with Controls and Properties

from the Master Page

When working with master pages from a content page, you actually have good access to the controls

and the properties that the master page exposes The master page, when referenced by the content page, exposes a property calledMaster You use this property to get at control values or custom properties that are contained in the master page itself

To see an example of this, create a GUID (unique identifier) in the master page that you can retrieve

on the content page that is using the master For this example, use the master page that was created in

Listing 5-1, but add a Label server control and thePage_Loadevent (see Listing 5-8)

Listing 5-8: A master page that creates a GUID on the first request

VB

<%@ Master Language="VB" %>

<script runat="server">

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs)

If Not Page.IsPostBack Then Label1.Text = System.Guid.NewGuid().ToString() End If

End Sub

</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>

<b>User’s GUID:&nbsp;&nbsp;

<asp:Label ID="Label1" runat="server" /></b>

</td>

</tr>

<tr>

<td>

<asp:ContentPlaceHolder ID="ContentPlaceHolder1"

runat="server">

</asp:ContentPlaceHolder>

<td>

<asp:ContentPlaceHolder ID="ContentPlaceHolder2"

runat="server">

</asp:ContentPlaceHolder>

</td>

</tr>

<tr>

<td colspan="2">

Copyright 2008 - My Company

</td>

</tr>

</table>

</form>

</body>

</html>

C#

protected void Page_Load(object sender, EventArgs e)

{

if (!Page.IsPostBack) {

Label1.Text = System.Guid.NewGuid().ToString();

} }

Now you have a Label control on the master page that you can access from the content page You have

a couple of ways to accomplish this task The first is to use theFindControl()method that the master

page exposes This approach is shown in Listing 5-9

Listing 5-9: Getting at the Label’s Text value in the content page

VB

<%@ Page Language="VB" MasterPageFile="~/Wrox.master" %>

<script runat="server" language="vb">

Protected Sub Page_LoadComplete(ByVal sender As Object, _

ByVal e As System.EventArgs)

Label1.Text = CType(Master.FindControl("Label1"), Label).Text End Sub

Protected Sub Button1_Click(ByVal sender As Object, _

ByVal e As System.EventArgs)

Label2.Text = "Hello " & TextBox1.Text & "!"

End Sub

</script>

<asp:Content ID="Content1" ContentPlaceHolderID="head" Runat="Server">

</asp:Content>

<asp:Content ID="Content2" ContentPlaceHolderId="ContentPlaceHolder1"