|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 <[email protected]%> in a normal ASPX page, the master page has a <[email protected] %> 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 <[email protected]%> 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|
In the next forty months – just over three years – businesses will undergo extraordinary changes. The exponential growth of digitization and machine learning will see a step function change in how businesses create value, satisfy customers, and outperform their competition. In the next forty months companies will take the actions that will see them get to the next level of the game called Capitalism. Or they won’t – game over. The winners of today and tomorrow think differently, follow different...
Oct. 26, 2016 02:30 AM EDT Reads: 1,060
“Media Sponsor” of SYS-CON's 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. CloudBerry Backup is a leading cross-platform cloud backup and disaster recovery solution integrated with major public cloud services, such as Amazon Web Services, Microsoft Azure and Google Cloud Platform.
Oct. 26, 2016 02:30 AM EDT Reads: 1,467
The Internet of Things (IoT), in all its myriad manifestations, has great potential. Much of that potential comes from the evolving data management and analytic (DMA) technologies and processes that allow us to gain insight from all of the IoT data that can be generated and gathered. This potential may never be met as those data sets are tied to specific industry verticals and single markets, with no clear way to use IoT data and sensor analytics to fulfill the hype being given the IoT today.
Oct. 26, 2016 01:45 AM EDT Reads: 2,729
Ask someone to architect an Internet of Things (IoT) solution and you are guaranteed to see a reference to the cloud. This would lead you to believe that IoT requires the cloud to exist. However, there are many IoT use cases where the cloud is not feasible or desirable. In his session at @ThingsExpo, Dave McCarthy, Director of Products at Bsquare Corporation, will discuss the strategies that exist to extend intelligence directly to IoT devices and sensors, freeing them from the constraints of ...
Oct. 26, 2016 01:15 AM EDT Reads: 3,107
SYS-CON Events announced today that SoftNet Solutions will exhibit at the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. SoftNet Solutions specializes in Enterprise Solutions for Hadoop and Big Data. It offers customers the most open, robust, and value-conscious portfolio of solutions, services, and tools for the shortest route to success with Big Data. The unique differentiator is the ability to architect and ...
Oct. 26, 2016 12:00 AM EDT Reads: 1,045
The Internet of Things will challenge the status quo of how IT and development organizations operate. Or will it? Certainly the fog layer of IoT requires special insights about data ontology, security and transactional integrity. But the developmental challenges are the same: People, Process and Platform and how we integrate our thinking to solve complicated problems. In his session at 19th Cloud Expo, Craig Sproule, CEO of Metavine, will demonstrate how to move beyond today's coding paradigm ...
Oct. 26, 2016 12:00 AM EDT Reads: 3,865
Fifty billion connected devices and still no winning protocols standards. HTTP, WebSockets, MQTT, and CoAP seem to be leading in the IoT protocol race at the moment but many more protocols are getting introduced on a regular basis. Each protocol has its pros and cons depending on the nature of the communications. Does there really need to be only one protocol to rule them all? Of course not. In his session at @ThingsExpo, Chris Matthieu, co-founder and CTO of Octoblu, walk you through how Oct...
Oct. 26, 2016 12:00 AM EDT Reads: 3,192
A completely new computing platform is on the horizon. They’re called Microservers by some, ARM Servers by others, and sometimes even ARM-based Servers. No matter what you call them, Microservers will have a huge impact on the data center and on server computing in general. Although few people are familiar with Microservers today, their impact will be felt very soon. This is a new category of computing platform that is available today and is predicted to have triple-digit growth rates for some ...
Oct. 26, 2016 12:00 AM EDT Reads: 34,222
Everyone knows that truly innovative companies learn as they go along, pushing boundaries in response to market changes and demands. What's more of a mystery is how to balance innovation on a fresh platform built from scratch with the legacy tech stack, product suite and customers that continue to serve as the business' foundation. In his General Session at 19th Cloud Expo, Michael Chambliss, Head of Engineering at ReadyTalk, will discuss why and how ReadyTalk diverted from healthy revenue an...
Oct. 25, 2016 11:45 PM EDT Reads: 2,995
In past @ThingsExpo presentations, Joseph di Paolantonio has explored how various Internet of Things (IoT) and data management and analytics (DMA) solution spaces will come together as sensor analytics ecosystems. This year, in his session at @ThingsExpo, Joseph di Paolantonio from DataArchon, will be adding the numerous Transportation areas, from autonomous vehicles to “Uber for containers.” While IoT data in any one area of Transportation will have a huge impact in that area, combining sensor...
Oct. 25, 2016 10:45 PM EDT Reads: 997
For basic one-to-one voice or video calling solutions, WebRTC has proven to be a very powerful technology. Although WebRTC’s core functionality is to provide secure, real-time p2p media streaming, leveraging native platform features and server-side components brings up new communication capabilities for web and native mobile applications, allowing for advanced multi-user use cases such as video broadcasting, conferencing, and media recording.
Oct. 25, 2016 08:45 PM EDT Reads: 3,246
Established in 1998, Calsoft is a leading software product engineering Services Company specializing in Storage, Networking, Virtualization and Cloud business verticals. Calsoft provides End-to-End Product Development, Quality Assurance Sustenance, Solution Engineering and Professional Services expertise to assist customers in achieving their product development and business goals. The company's deep domain knowledge of Storage, Virtualization, Networking and Cloud verticals helps in delivering ...
Oct. 25, 2016 08:30 PM EDT Reads: 1,108
SYS-CON Events announced today that Enzu will exhibit at the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. Enzu’s mission is to be the leading provider of enterprise cloud solutions worldwide. Enzu enables online businesses to use its IT infrastructure to their competitive advantage. By offering a suite of proven hosting and management services, Enzu wants companies to focus on the core of their online busine...
Oct. 25, 2016 08:15 PM EDT Reads: 1,378
In the next five to ten years, millions, if not billions of things will become smarter. This smartness goes beyond connected things in our homes like the fridge, thermostat and fancy lighting, and into heavily regulated industries including aerospace, pharmaceutical/medical devices and energy. “Smartness” will embed itself within individual products that are part of our daily lives. We will engage with smart products - learning from them, informing them, and communicating with them. Smart produc...
Oct. 25, 2016 07:30 PM EDT Reads: 1,544
November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. Penta Security is a leading vendor for data security solutions, including its encryption solution, D’Amo. By using FPE technology, D’Amo allows for the implementation of encryption technology to sensitive data fields without modification to schema in the database environment. With businesses having their data become increasingly more complicated in their mission-critical applications (such as ERP, CRM, HRM), continued ...
Oct. 25, 2016 07:30 PM EDT Reads: 1,127
OnProcess Technology has announced it will be a featured speaker at @ThingsExpo, taking place November 1 - 3, 2016, in Santa Clara, California. Dan Gettens, OnProcess’ Chief Analytics Officer, will discuss how Internet of Things (IoT) data can be leveraged to predict product failures, improve uptime and slash costly inventory stock. @ThingsExpo is an annual gathering of IoT and cloud developers, practitioners and thought-leaders who exchange ideas and insights on topics ranging from Big Data in...
Oct. 25, 2016 07:15 PM EDT Reads: 338
SYS-CON Events announced today that Cloudbric, a leading website security provider, will exhibit at the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. Cloudbric is an elite full service website protection solution specifically designed for IT novices, entrepreneurs, and small and medium businesses. First launched in 2015, Cloudbric is based on the enterprise level Web Application Firewall by Penta Security Sys...
Oct. 25, 2016 06:45 PM EDT Reads: 1,250
SYS-CON Events announced today that Transparent Cloud Computing (T-Cloud) Consortium will exhibit at the 19th International Cloud Expo®, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. The Transparent Cloud Computing Consortium (T-Cloud Consortium) will conduct research activities into changes in the computing model as a result of collaboration between "device" and "cloud" and the creation of new value and markets through organic data proces...
Oct. 25, 2016 06:45 PM EDT Reads: 1,449
SYS-CON Events announced today that Roundee / LinearHub will exhibit at the WebRTC Summit at @ThingsExpo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. LinearHub provides Roundee Service, a smart platform for enterprise video conferencing with enhanced features such as automatic recording and transcription service. Slack users can integrate Roundee to their team via Slack’s App Directory, and '/roundee' command lets your video conference ...
Oct. 25, 2016 06:15 PM EDT Reads: 2,149
Successful digital transformation requires new organizational competencies and capabilities. Research tells us that the biggest impediment to successful transformation is human; consequently, the biggest enabler is a properly skilled and empowered workforce. In the digital age, new individual and collective competencies are required. In his session at 19th Cloud Expo, Bob Newhouse, CEO and founder of Agilitiv, will draw together recent research and lessons learned from emerging and established ...
Oct. 25, 2016 05:45 PM EDT Reads: 1,466