#code expressions

Code Expressions

Code expressions can be used in Razor views to pull out data from your model or contain expressions for Razor to evaluate and then display as text. The "@" symbol is used to indicate a code expression.

If your model is enumerable, a couple methods are available to you.

<!-- The model is a list of restaurant reviews --> @model IEnumerable <!-- .First() gives you the first review in the list --> <p>Name of the first reviewer: @Model.First().Name</p> <!-- .Last() give you the last review in the list --> <p>Rating from the last review: @Model.Last().Rating</p> <!-- .Count() returns the number of reviews in the list --> <p>Number of reviews for the restaurant: @Model.Count()</p>

Note: You can add comments to .cshtml files, which will not be visible in the output html file by placing the comment between "@*" and "*@". @* Commented out code *@

Implicit vs Explicit C# Code Expressions

When using implicit C# code, we let Razor figure out what is C# code and what is markup. Razor is able to parse the line of code below correctly. <p>The number is @item.Number</p>

But what if you wanted to divide the number by 10? Doing the code below will display "/ 10" as text and not include it in the C# expression for evaluation. <span>@item.Number / 10</span>

This is where explicit C# code expressions are useful. Simply wrap the entire expression in parentheses after the "@" symbol as seen below. Now the @item.Number is divided by 10 and then displayed. <span>The number divided by 10 is @(item.Number / 10)</span>

Razor is generally good at differentiating between C# code and markup, but there are a couple gotchas. Below are some of the common ones.

If you want to add the "@" symbol as text before some text, such as a twitter handle, you will need to escape the "@" sign via another "@" symbol. This way, it doesn't think the twitter handle is C# code that needs to be evaluated. <p>Twitter Handle: @@TwitterName</p>

Another gotcha is when you use want to append some text, such as the letter 'R' to a rating score stored in a model property. You want it to display something like "R5". The below code will NOT work. <span>Incorrect: [email protected]</span>

It will assume "@item.Rating" is text. This assumption is default so it is easier to display email addresses which follow the format of something@something. To get around this, just use explicit C# expressions. <span>Correct: R@(Item.Rating)</span>

Tidbit: The @VirtualPath property is inherited by views and can be used to display the virtual path of the view.

Code Blocks

You can make C# code blocks in .cshtml files to write multiple lines of consecutive C# code. Code blocks allow you to do the same things you can do in .cs files. You can change properties of the ViewBag and even declare variables, which can be used anywhere in the .cshtml file after the variable declaration.

@ { ViewBag.Title = "New Title"; int num = 5; }

For each statements work a little differently to make it easier to read, write, and transition between C# code and markup. We can use the for each statement to iterate through a list of items in a model and display their properties one by one. Razor is smart enough to differentiate between C# and the table markup so we can write code like the example below.

@foreach (var item in Model) { <td> @Html.DisplayFor(modelItem => item.Name) </td> <td> @Html.DisplayFor(modelItem => item.Rating) </td> ... }

However, adding the literal text "Review" at the top of the for each statement causes an error as Razor thinks it's C# code.

@foreach (var item in Model) { // Causes an error! Review <td> @Html.DisplayFor(modelItem => item.Name) </td> <td> @Html.DisplayFor(modelItem => item.Rating) </td> ... }

To solve this problem, you can indicate that "Review" is literal text by adding "@:" before it as shown below. @:Review