|By Jeevan Murkoth||
|December 7, 2004 12:00 AM EST||
Since the advent of Web development, Web developers have sought a way to provide a consistent look and feel across the Web application. This pursuit has resulted in different custom solutions. With the introduction of master pages in ASP.NET 2.0, Microsoft has finally brought the support to the framework level and has given the developers what they have been asking for. Master pages, as the name suggests, allow the developer to define the layout in a single page and easily apply the layout to multiple pages across the Web site, thereby ensuring a consistent appearance. This article looks at how we use master pages with the help of some examples. We will also look at some of the new features that are available in ASP.NET 2.0.
Master pages allow the developer to take a compartmentalized approach while developing Web sites. It allows the developer to move standardized layouts like header, footer, navigation, or any other content that is common over multiple pages to the master page. Content that is specific to a particular page can be defined in content pages that we will see in the next section. Master pages are transparent to the users and when a request is made to the URL of the content page, ASP.NET merges the content of the content page with that of the master page and renders the resulting page. Unlike ordinary ASPX pages, a Web server does not serve a master page and if a user makes a request to the master page, the server returns an error message (see Figure 1).
Master pages are like any other ASP.NET pages with a couple of exceptions. They are identified by a .master file extension. Listing 1 (the code is online at www.sys-con.com/dotnet/source.cfm) is an example of a simple master page. Note that instead of the familiar page directive <%@Page%> in a normal ASPX page, the master page has a <%@Master %> directive. Master pages define ContentPlaceholder controls that act as placeholders where content from the content page will be inserted. ContentPlaceholder control is specific to master pages and cannot be declared in a content page. In this example we have defined one ContentPlaceholder control identified as ContentPlaceholder1. A master page can define zero to any number of ContentPlaceholder controls.
The content page is the actual page that a user will request from the server. Content pages are like typical ASPX pages and have a .ASPX extension. However, they differ from an ordinary ASPX page in two ways. The first difference is that a content page has to be associated with a master page, which is done by setting the MasterPageFile attribute in the page directive. Second, all of the content in a Web page must be defined inside a new content control. Any content that is defined outside the content control results in an error. The content control in turn has to be mapped to the Contentplaceholder controls that have been defined in the Master page. Listing 2 shows a content page that refers to Sample.master as its master page. In this example the content page defines a content control called Content1. This content control in turn is mapped to the ContentPlaceholder ContentPlaceHolder1 of the master page by setting the ContentPlaceHolderID.
Sequence of Events
Just like regular ASPX pages, master pages and content pages have events that are fired during the page life cycle. They can also have user controls that need to be initialized. The list below shows the sequence of events in a content page that references a master page.
- Controls in the master page are initialized
- Controls in the content page are initialized
- Master page is initialized
- Content page is initialized
- Content page loads
- Master page loads
- Master page controls load
- Content page controls load
Now that we have seen what a master page and a content page are, let's see how to create a master and content page using Visual Studio .NET 2005 Beta. Visual Studio allows us to add master pages by choosing an item of type Master Page in the Add New Item option. It also gives us the option to have a code behind page associated with the master page and also select the language of the page. In Figure 2, I add a master page called MyMaster1.master using the Add New Item dialog.
To the master page that I just created, I have added an image, footer, and two content placeholders. Each of the ContentPlaceholder controls that has been added has a unique ID which will be referred to by the content page to insert its content. Listing 3 shows the markup and Figure 3 shows the design view of the master page that I have created. Any content page that uses this master page will automatically inherit the image, the heading, and the footer.
Now that we have created the master page, let's go ahead and create a content page using the Add New Item option in Visual Studio .NET 2005 Beta (see Figure 4). A content page is just an ordinary Web form and Visual Studio .NET 2005 Beta does not have a special type called content page. When we create the content page, the Add New Item dialog, however, gives us the option to select the master page that will be referenced by the Web form. Once we select this option, Visual Studio presents us with a dialog box that lists all the master pages in the Web site (see Figure 5). Figure 6 shows the design view of the content page that we have just created. You will notice that all the master page content is grayed out and cannot be edited. Listing 4 shows the markup of the content page we just created. The only editable portion in the content page is between the <asp:Content> tags. Each of these content tags is linked to ContentPlaceholder of the master page by setting the ContentPlaceHolderID for the content control. In Listing 4, Content1 is mapped to ContentPlaceholder1 of the master page and Content2 is mapped to ContentPlaceholder2 of the master page. Content control in turn can contain other controls. In this example I have added some text in each of the content tags. Figure 7 shows the browser rendering of the content page.
Nesting Master Pages
Master pages can be nested and can have one master page refer to another as its master. Nested master pages are very useful while designing Web sites with different sections where each individual section has to have its own layout and at the same time be consistent with the overall appearance of the Web site. For example, in a corporate Web site we could have a master page that could define the global menu and a master page for each department that would define the departmental menu. Nesting the department master page and the corporate master page would allow us to combine the two menus. Visual Studio .NET 2005 Beta, however, does not provide designer support for nested master pages.
Let's look at how to create a nested master page with the help of an example. Listing 5 shows the parent master page, ParentMaster.master. This parent master page is then referred to by the child master page (see Listing 6). As you can see, the child master page is not very different from the parent master page. They have the same .master extension; however, the child master page has a content control that is mapped to the ContentPlaceHolder control defined in the parent master page. The child master page can also define ContentPlaceHolder controls of its own to display content of the content page that refers to this page as its master. The child master page in our example defines a content control that is mapped to ContentPlaceHolder1 of the master page. It defines a Contentplaceholder control of its own ChildContentPlaceHolder1 to which the content page will map its content. Listing 7 is the content page that refers to the child master page as its master page. Figure 8 shows the rendering of the content page that uses nested master pages.
Configuring a Site to Use Master Pages
Instead of giving the master attribute in the page directive of each and every page in a Website, ASP.NET 2.0 gives you the option to set the master page in the Web.config file. This is very useful in large Web sites as it gives the developers the flexibility to make the change at one place and apply it across the site. The code snippet below shows how to set the master page in the web.config file:
<pages masterPageFile="MyMaster1.master" />
A couple of things need to be pointed out about setting master pages through the web.config file. First, if the content page has a master page explicitly set in its page directive, that master page assumes precedence over the one set in the web.config file. If there are multiple master page settings in different web.config files, the master page setting in the immediate folder overrides the other setting similar to how in an application with multiple sub- folders, the setting of the web config in the immediate folder takes precedence over the others.
Accessing Master Page Controls from Content Pages
The developer may need to access the controls in the master page for many reasons. One could be to display a value that is relevant to the content page. ASP.NET 2.0 gives you multiple options to achieve this. The first step is to get a reference to the master page. In a content page, the Master property returns the reference to the master page. Once we have obtained the reference to the master page, it is now possible to refer to the controls of the master page. We will look at two approaches. The first approach is early binding, where the control is declared as a public property in the master page. Listing 8 shows the master page where we first expose the text of control Label2 as a public property LabelText. We then access and set the value of LabelText in the page load event of the content page as shown in Listing 9. Another thing to point out is the strong typed reference to the Master page using the <%@masterType%> directive in the Content page. This explicitly casts the value of the master property to the master page object which in our case is AccessMasterProperties.
The second approach is the late binding approach. Here we make use of the familiar FindControl method. We get a reference to a label control in the master page and change the text value from the content page. We search for the label by its ID which in this case is Label1 and then cast it to a label control and set the value for the text.
Dynamically Changing Master Pages
ASP.NET 2.0 allows the developer to change the master page associated with a content page dynamically at run-time. This is very useful if the developer would like to give the users the flexibility of choosing the master pages. The master page for a content page can be set programmatically by assigning a value to the MasterPagefile property of the page. However, this dynamic assignment can be done only in the preinit event of the content page since this is the earliest event that occurs in the page execution life cycle. If we attempt to set the master page file in events like pageload, it would result in an exception. Listing 10 shows an example where we have a dropdown list with the available master pages. On clicking the button we redirect the response to the same page and pass the value of the master page to be set as a request string. The MasterPagefile is then set in the preinit event.
Device-Specific Master Pages
ASP.NET 2.0 pages and controls have built-in support that enables them to automatically render appropriate content depending on the browser and the device that has requested the page. Master pages also support similar behavior. We can create a master page specifically for a device or a browser and in the content page instead of binding to a single master page. We can bind them to number of master pages, each of them specific to a particular device. The binding is qualified with the device name. Listing 11 shows a content page that is bound to two master pages, one for Internet explorer and another for mozilla. The Internet Explorer master page is prefixed with ie and the one for Mozilla is prefixed with Mozilla. These browser prefixes are defined in the browsercaps section of the machine.config file. Depending upon the browser requesting the page, the content page is bound to the appropriate master page. Figures 9 and 10 show the rendering of the content page when it is requested through the two different browsers, Mozilla and Internet Explorer. As you see, ASP.NET 2.0 has automatically chosen the appropriate master page.
In this article we looked at the concept of master pages and saw how they allow the developer to easily create reusable page layouts. It also greatly simplifies maintenance as it is now possible to make changes at one place and propagate them throughout the Web site. I am sure that this feature will have a significant impact on how ASP.NET applications are built in the future.
|Mujtaba Syed 12/14/04 03:48:48 PM EST|
SYS-CON Events announced today that HPM Networks will exhibit at the 17th International Cloud Expo®, which will take place on November 3–5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. For 20 years, HPM Networks has been integrating technology solutions that solve complex business challenges. HPM Networks has designed solutions for both SMB and enterprise customers throughout the San Francisco Bay Area.
Aug. 2, 2015 05:45 PM EDT Reads: 505
For IoT to grow as quickly as analyst firms’ project, a lot is going to fall on developers to quickly bring applications to market. But the lack of a standard development platform threatens to slow growth and make application development more time consuming and costly, much like we’ve seen in the mobile space. In his session at @ThingsExpo, Mike Weiner, Product Manager of the Omega DevCloud with KORE Telematics Inc., discussed the evolving requirements for developers as IoT matures and conducted a live demonstration of how quickly application development can happen when the need to comply wit...
Aug. 2, 2015 11:15 AM EDT Reads: 354
The Internet of Everything (IoE) brings together people, process, data and things to make networked connections more relevant and valuable than ever before – transforming information into knowledge and knowledge into wisdom. IoE creates new capabilities, richer experiences, and unprecedented opportunities to improve business and government operations, decision making and mission support capabilities.
Aug. 1, 2015 10:00 AM EDT Reads: 335
Explosive growth in connected devices. Enormous amounts of data for collection and analysis. Critical use of data for split-second decision making and actionable information. All three are factors in making the Internet of Things a reality. Yet, any one factor would have an IT organization pondering its infrastructure strategy. How should your organization enhance its IT framework to enable an Internet of Things implementation? In his session at @ThingsExpo, James Kirkland, Red Hat's Chief Architect for the Internet of Things and Intelligent Systems, described how to revolutionize your archit...
Jul. 30, 2015 07:30 PM EDT Reads: 1,421
MuleSoft has announced the findings of its 2015 Connectivity Benchmark Report on the adoption and business impact of APIs. The findings suggest traditional businesses are quickly evolving into "composable enterprises" built out of hundreds of connected software services, applications and devices. Most are embracing the Internet of Things (IoT) and microservices technologies like Docker. A majority are integrating wearables, like smart watches, and more than half plan to generate revenue with APIs within the next year.
Jul. 30, 2015 02:30 PM EDT Reads: 140
Growth hacking is common for startups to make unheard-of progress in building their business. Career Hacks can help Geek Girls and those who support them (yes, that's you too, Dad!) to excel in this typically male-dominated world. Get ready to learn the facts: Is there a bias against women in the tech / developer communities? Why are women 50% of the workforce, but hold only 24% of the STEM or IT positions? Some beginnings of what to do about it! In her Opening Keynote at 16th Cloud Expo, Sandy Carter, IBM General Manager Cloud Ecosystem and Developers, and a Social Business Evangelist, d...
Jul. 30, 2015 12:00 PM EDT Reads: 2,079
In his keynote at 16th Cloud Expo, Rodney Rogers, CEO of Virtustream, discussed the evolution of the company from inception to its recent acquisition by EMC – including personal insights, lessons learned (and some WTF moments) along the way. Learn how Virtustream’s unique approach of combining the economics and elasticity of the consumer cloud model with proper performance, application automation and security into a platform became a breakout success with enterprise customers and a natural fit for the EMC Federation.
Jul. 30, 2015 09:00 AM EDT Reads: 2,173
The Internet of Things is not only adding billions of sensors and billions of terabytes to the Internet. It is also forcing a fundamental change in the way we envision Information Technology. For the first time, more data is being created by devices at the edge of the Internet rather than from centralized systems. What does this mean for today's IT professional? In this Power Panel at @ThingsExpo, moderated by Conference Chair Roger Strukhoff, panelists addressed this very serious issue of profound change in the industry.
Jul. 29, 2015 03:00 PM EDT Reads: 1,299
Discussions about cloud computing are evolving into discussions about enterprise IT in general. As enterprises increasingly migrate toward their own unique clouds, new issues such as the use of containers and microservices emerge to keep things interesting. In this Power Panel at 16th Cloud Expo, moderated by Conference Chair Roger Strukhoff, panelists addressed the state of cloud computing today, and what enterprise IT professionals need to know about how the latest topics and trends affect their organization.
Jul. 29, 2015 02:00 PM EDT Reads: 1,205
It is one thing to build single industrial IoT applications, but what will it take to build the Smart Cities and truly society-changing applications of the future? The technology won’t be the problem, it will be the number of parties that need to work together and be aligned in their motivation to succeed. In his session at @ThingsExpo, Jason Mondanaro, Director, Product Management at Metanga, discussed how you can plan to cooperate, partner, and form lasting all-star teams to change the world and it starts with business models and monetization strategies.
Jul. 28, 2015 04:30 PM EDT Reads: 1,776
Converging digital disruptions is creating a major sea change - Cisco calls this the Internet of Everything (IoE). IoE is the network connection of People, Process, Data and Things, fueled by Cloud, Mobile, Social, Analytics and Security, and it represents a $19Trillion value-at-stake over the next 10 years. In her keynote at @ThingsExpo, Manjula Talreja, VP of Cisco Consulting Services, discussed IoE and the enormous opportunities it provides to public and private firms alike. She will share what businesses must do to thrive in the IoE economy, citing examples from several industry sectors.
Jul. 28, 2015 11:00 AM EDT Reads: 2,049
There will be 150 billion connected devices by 2020. New digital businesses have already disrupted value chains across every industry. APIs are at the center of the digital business. You need to understand what assets you have that can be exposed digitally, what their digital value chain is, and how to create an effective business model around that value chain to compete in this economy. No enterprise can be complacent and not engage in the digital economy. Learn how to be the disruptor and not the disruptee.
Jul. 27, 2015 10:00 AM EDT Reads: 2,044
Akana has released Envision, an enhanced API analytics platform that helps enterprises mine critical insights across their digital eco-systems, understand their customers and partners and offer value-added personalized services. “In today’s digital economy, data-driven insights are proving to be a key differentiator for businesses. Understanding the data that is being tunneled through their APIs and how it can be used to optimize their business and operations is of paramount importance,” said Alistair Farquharson, CTO of Akana.
Jul. 27, 2015 09:00 AM EDT Reads: 334
Business as usual for IT is evolving into a "Make or Buy" decision on a service-by-service conversation with input from the LOBs. How does your organization move forward with cloud? In his general session at 16th Cloud Expo, Paul Maravei, Regional Sales Manager, Hybrid Cloud and Managed Services at Cisco, discusses how Cisco and its partners offer a market-leading portfolio and ecosystem of cloud infrastructure and application services that allow you to uniquely and securely combine cloud business applications and services across multiple cloud delivery models.
Jul. 27, 2015 08:00 AM EDT Reads: 1,910
The enterprise market will drive IoT device adoption over the next five years. In his session at @ThingsExpo, John Greenough, an analyst at BI Intelligence, division of Business Insider, analyzed how companies will adopt IoT products and the associated cost of adopting those products. John Greenough is the lead analyst covering the Internet of Things for BI Intelligence- Business Insider’s paid research service. Numerous IoT companies have cited his analysis of the IoT. Prior to joining BI Intelligence, he worked analyzing bank technology for Corporate Insight and The Clearing House Payment...
Jul. 26, 2015 09:00 PM EDT Reads: 1,588
"Optimal Design is a technology integration and product development firm that specializes in connecting devices to the cloud," stated Joe Wascow, Co-Founder & CMO of Optimal Design, in this SYS-CON.tv interview at @ThingsExpo, held June 9-11, 2015, at the Javits Center in New York City.
Jul. 25, 2015 02:00 PM EDT Reads: 404
SYS-CON Events announced today that CommVault has been named “Bronze Sponsor” of SYS-CON's 17th International Cloud Expo®, which will take place on November 3–5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. A singular vision – a belief in a better way to address current and future data management needs – guides CommVault in the development of Singular Information Management® solutions for high-performance data protection, universal availability and simplified management of data on complex storage networks. CommVault's exclusive single-platform architecture gives companies unp...
Jul. 25, 2015 01:00 PM EDT Reads: 1,973
Electric Cloud and Arynga have announced a product integration partnership that will bring Continuous Delivery solutions to the automotive Internet-of-Things (IoT) market. The joint solution will help automotive manufacturers, OEMs and system integrators adopt DevOps automation and Continuous Delivery practices that reduce software build and release cycle times within the complex and specific parameters of embedded and IoT software systems.
Jul. 25, 2015 12:15 PM EDT Reads: 486
"ciqada is a combined platform of hardware modules and server products that lets people take their existing devices or new devices and lets them be accessible over the Internet for their users," noted Geoff Engelstein of ciqada, a division of Mars International, in this SYS-CON.tv interview at @ThingsExpo, held June 9-11, 2015, at the Javits Center in New York City.
Jul. 25, 2015 12:00 PM EDT Reads: 1,553
Internet of Things is moving from being a hype to a reality. Experts estimate that internet connected cars will grow to 152 million, while over 100 million internet connected wireless light bulbs and lamps will be operational by 2020. These and many other intriguing statistics highlight the importance of Internet powered devices and how market penetration is going to multiply many times over in the next few years.
Jul. 25, 2015 09:00 AM EDT Reads: 1,502