Basic Programming Concepts Using Razer syntax
The Razor syntax, you can quickly create dynamic web pages with sophisticated features, and it won't take much code to get things done. It isn't an exhaustive examination, just a quick tour through the programming concepts you'll use most often.The Razor Syntax, Server Code, and ASP.NET
Razor syntax is a simple programming syntax for embedding server-based code in a web page. In a web page that uses the Razor syntax, there are two kinds of content: client content and server code. Client content is the stuff you're used to in web pages: HTML markup (elements), style information such as CSS, client script such as JavaScript, and plain text.Razor syntax lets you add server code to this client content. If there's server code in the page, the server runs that code first, before it sends the page to the browser. By running on the server, the code can perform tasks that can be a lot more complex to do using client content alone, like accessing server-based databases. Most importantly, server code can dynamically create client content — it can generate HTML markup or other content on the fly and then send it to the browser along with any static HTML that the page might contain. From the browser's perspective, client content that's generated by your server code is no different than any other client content. As you've already seen, the server code that's required is quite simple.
ASP.NET web pages that include the Razor syntax have a special file extension (.cshtml or .vbhtml). The server recognizes these extensions, runs the code that's marked with Razor syntax, and then sends the page to the browser.
Where does ASP.NET fit in?
Razor syntax is based on a technology from Microsoft called ASP.NET, which in turn is based on the Microsoft .NET Framework. The.NET Framework is a big, comprehensive programming framework from Microsoft for developing virtually any type of computer application. ASP.NET is the part of the .NET Framework that's specifically designed for creating web applications. Developers have used ASP.NET to create many of the largest and highest-traffic websites in the world. (Any time you see the file-name extension .aspx as part of the URL in a site, you'll know that the site was written using ASP.NET.)The Razor syntax gives you all the power of ASP.NET, but using a simplified syntax that's easier to learn if you're a beginner and that makes you more productive if you're an expert. Even though this syntax is simple to use, its family relationship to ASP.NET and the .NET Framework means that as your websites become more sophisticated, you have the power of the larger frameworks available to you.
Language and Syntax
Earlier you saw a basic example of how to create an ASP.NET Web Pages page, and how you can add server code to HTML markup. Here you'll learn the basics of writing ASP.NET server code using the Razor syntax — that is, the programming language rules.If you're experienced with programming (especially if you've used C, C++, C#, Visual Basic, or JavaScript), much of what you read here will be familiar. You'll probably need to familiarize yourself only with how server code is added to markup in .cshtml files.
Basic Syntax
Combining Text, Markup, and Code in Code Blocks
In server code blocks, you'll often want to output text or markup (or both) to the page. If a server code block contains text that's not code and that instead should be rendered as is, ASP.NET needs to be able to distinguish that text from code. There are several ways to do this.- Enclose the text in an HTML element like
<p></p>or<em></em>:
@if(IsPost) { // This line has all content between matched <p> tags. <p>Hello, the time is @DateTime.Now and this page is a postback!</p> } else { // All content between matched tags, followed by server code. <p>Hello <em>stranger</em>, today is: <br /> </p> @DateTime.Now }
The HTML element can include text, additional HTML elements, and server-code expressions. When ASP.NET sees the opening HTML tag, it renders everything including the element and its content as is to the browser (and resolves the server-code expressions).
- Use the
@:operator or the<text>element. The@:outputs a single line of content containing plain text or unmatched HTML tags; the<text>element encloses multiple lines to output. These options are useful when you don't want to render an HTML element as part of the output.
@if(IsPost) { // Plain text followed by an unmatched HTML tag and server code. @: The time is: <br /> @DateTime.Now // Server code and then plain text, matched tags, and more text. @DateTime.Now @:is the <em>current</em> time. }
If you want to output multiple lines of text or unmatched HTML tags, you can precede each line with@:, or you can enclose the line in a<text>element. Like the@:operator,<text>tags are used by ASP.NET to identify text content and are never rendered in the page output.
@if(IsPost) { // Repeat the previous example, but use <text> tags. <text> The time is: <br /> @DateTime.Now @DateTime.Now is the <em>current</em> time. </text> } @{ var minTemp = 75; <text>It is the month of @DateTime.Now.ToString("MMMM"), and it's a <em>great</em> day! <br /><p>You can go swimming if it's at least @minTemp degrees. </p></text> }
The first example repeats the previous example but uses a single pair of<text>tags to enclose the text to render. In the second example, the<text>and</text>tags enclose three lines, all of which have some uncontained text and unmatched HTML tags (<br />), along with server code and matched HTML tags. Again, you could also precede each line individually with the@:operator; either way works.
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