Introduction to razor

The main purpose of razor syntax is to makeCodeIt can work with the marking stream without conflict with control characters. For example, the following aspx code:

<Ul>

<% Foreach (var p in model. Products) {%>

<Li> <% = P. name %> ($ <% = P. Price %>) </LI>

<% }%>

</Ul>

Now, we only keep what we actually pay attention to and remove the extra aspx control characters. The processed code is as follows:

<Ul>

Foreach (var p in model. Products ){

<Li> P. Name ($ P. Price) </LI>

}

</Ul>

Obviously, the above Code does not have enough information to determine the code and the tags. When designing the razor engine, we hope to add as little information as possible to distinguish the code and markup in the above Code. Pages Based on the razor engine contain code, tags, and as few additional tags as possible. Therefore, using the C # razor syntax, the above Code becomes:

<Ul>

@ Foreach (var p in model. Products ){

<Li> @ P. Name ($ @ P. Price) </LI>

}

</Ul> 

This is not a complement to the aspx syntax. Razor uses a full understanding of C # (or VB) and HTML syntax to deduce the code you want to write. Let's continue with the above example. Let's take a step-by-step look at how razor resolves it.

<Ul>

Razor parses forward until it encounters the "@" character, so this line of razor will classify <ul> As a tag and go to the next line for processing.

@ Foreach (var p in model. Products ){

Now, Razor finds a "@" character. "@" is a magic character in razor. Unlike "<%=%>" in aspx, it only has one character, next, the parser calculates the remaining content. In aspx, we declare the end of the code block through "%>", but Razor does not have its own syntax to declare the end of the code block. Razor uses the least match mode and language-based syntax to determine the end of a code block. In the above case, Razor knows that the foreach declaration in C # is included in the "{" and "}" characters, so when the foreach declaration ends, the parsing engine returns the flag status.

<Li> @ P. Name ($ @ P. Price) </LI>

I just said that the parser will be in code mode before it reaches the foreach end. What should I do with this code? This code is more like a tag, but we are still in the foreach declaration code block. In fact, this is another situation where razor uses language-based syntax to deduce your intention. We know that there will be some declaration statements after the "{" character,, we found the "<li>" mark rather than the declaration statement. At this time, razor will infer that you actually want to switch to the tag resolution rather than the code resolution status. So what we actually get is the stack with three kinds of context information: the first is to mark the status; switch to the code status through @ foreach, and switch back to the flag status through "<li>; at the end of the "<li>" mark, It is inferred that the Code status of the foreach subject has been returned.

}

Then, it is parsed to the end "}" character of the foreach statement block and returned to the tag context.

</Ul>

Next, we will continue to parse the mark until the next "@" character or the end of the file is reached.

View the next article: razor insider Analysis

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