ASP.NET Razor - C# and VB Code Syntax
Razor supports both C# (C sharp) and VB (Visual Basic).
Main Razor Syntax Rules for C#
- Razor code blocks are enclosed in @{ ... }
- Inline expressions (variables and functions) start with @
- Code statements end with semicolon
- Variables are declared with the var keyword
- Strings are enclosed with quotation marks
- C# code is case sensitive
- C# files have the extension .cshtml
C# Example
<!-- Single statement block -->
@{ var myMessage = "Hello World"; }
<!-- Inline expression or variable -->
<p>The value of myMessage is: @myMessage</p>
<!-- Multi-statement block -->
@{
var greeting = "Welcome to our site!";
var weekDay = DateTime.Now.DayOfWeek;
var greetingMessage = greeting + " Here in Huston it is: " + weekDay;
}
<p>The greeting is: @greetingMessage</p>
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Main Razor Syntax Rules for VB
- Razor code blocks are enclosed in @Code ... End Code
- Inline expressions (variables and functions) start with @
- Variables are declared with the Dim keyword
- Strings are enclosed with quotation marks
- VB code is not case sensitive
- VB files have the extension .vbhtml
Example
<!-- Single statement block -->
@Code dim myMessage = "Hello World" End Code
<!-- Inline expression or variable -->
<p>The value of myMessage is: @myMessage</p>
<!-- Multi-statement block -->
@Code
dim greeting = "Welcome to our site!"
dim weekDay = DateTime.Now.DayOfWeek
dim greetingMessage = greeting & " Here in Huston it is: " & weekDay
End Code
<p>The greeting is: @greetingMessage</p>
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How Does it Work?
Razor is a simple programming syntax for embedding server code in web pages.
Razor syntax is based on the ASP.NET framework, the part of the Microsoft.NET Framework that's specifically designed for creating web applications.
The Razor syntax gives you all the power of ASP.NET, but is using a simplified syntax that's easier to learn if you're a beginner, and makes you more productive if you're an expert.
Razor web pages can be described as HTML pages with two kinds of content: HTML content and Razor code.
When the server reads the page, it runs the Razor code first, before it sends the HTML page to the browser. The code that is executed on the server can perform tasks that cannot be done in the browser, for example accessing a server database. Server code can create dynamic HTML content on the fly, before it is sent to the browser. Seen from the browser, the HTML generated by server code is no different than static HTML content.
ASP.NET web pages with Razor syntax have the special file extension cshtml (Razor using C#) or vbhtml (Razor using VB).
Working With Objects
Server coding often involves objects.
The "DateTime" object is a typical
built-in ASP.NET object, but objects can also be self-defined, a web page, a text box, a file,
a database record, etc.
Objects may have methods they can perform. A
database record might have a "Save" method, an image object might have a
"Rotate" method, an email object might have a "Send" method,
and so on.
Objects
also have properties that describe their characteristics. A database record
might have a FirstName and a LastName property (among others).
The ASP.NET
DateTime object has a Now property (written as DateTime.Now), and the Now property has a
Day property (written as DateTime.Now.Day). The example below shows how to
access some properties of the DateTime object:
Example
<table border="1">
<tr>
<th
width="100px">Name</th>
<td width="100px">Value</td>
</tr>
<tr>
<td>Day</td><td>@DateTime.Now.Day</td>
</tr>
<tr>
<td>Hour</td><td>@DateTime.Now.Hour</td>
</tr>
<tr>
<td>Minute</td><td>@DateTime.Now.Minute</td>
</tr>
<tr>
<td>Second</td><td>@DateTime.Now.Second</td>
</tr>
</td>
</table>
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If and Else Conditions
An important feature of dynamic web pages is that you can determine what to do based on conditions.
The common way to do this is with the if ... else statements:
Example
@{
var txt = "";
if(DateTime.Now.Hour > 12)
{txt = "Good Evening";}
else
{txt = "Good Morning";}
}
<html>
<body>
<p>The message is @txt</p>
</body>
</html>
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Reading User Input
Another important feature of dynamic web pages is that you can read user input.
Input is read by the Request[] function, and posting (input) is tested by the IsPost condition:
Example
@{
var totalMessage = "";
if(IsPost)
{
var num1 = Request["text1"];
var num2 = Request["text2"];
var total = num1.AsInt() + num2.AsInt();
totalMessage =
"Total = " + total;
}
}
<html>
<body
style="background-color: beige; font-family: Verdana, Arial;">
<form
action="" method="post">
<p><label for="text1">First Number:</label><br>
<input type="text" name="text1" /></p>
<p><label for="text2">Second
Number:</label><br>
<input type="text" name="text2" /></p>
<p><input
type="submit" value=" Add " /></p>
</form>
<p>@totalMessage</p>
</body>
</html>
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