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Please clarify the use of => in MVC Razor. For example, in the context of a statement such as:

@Html.LabelFor(m => m.AnswerText)
John H
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winbacker
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  • It doesn't mean equal or bigger than, it points out that m refers to the model, specific to the AnswerText property. – Max Dec 30 '13 at 21:03

4 Answers4

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=> is a lambda expression. Basically it's short hand for selecting the value of one of the parameters in your model. For instance if you have 

@model YourDomain.Foo.Models.Bar

and in your Bar model you have a string called UserName then using @Html.TextBoxFor(m => m.UserName) will display the value of the user name in the model. ie (John Smith) When using a LabelFor however instead of it displaying the value of the Model parameter it displays the name of the model parameter so in your example where you are using

@Html.LabelFor(m => m.AnswerText)

your resulting display will be AnswerText

AaronH
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In that context (and any other), it's a lambda expression.

You need to use a lambda expression, you can't just call the method with Model.AnswerText. If you use Model.AnswerText it would just work as a regular parameter to a method. When you use a lambda expression as a parameter, the method can look at the model metadata, to get a name (for the html element) and the value (along with other things).

Steen Tøttrup
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It's a lambda operator, just like anywhere else in C#. In this case LabelFor is an extension method with parameter expression that returns model property value (right side).

Paul Petrov
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It's as simple as saying => implies that the word preceding the => is a placeholder variable.

More info here and here

Jose
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