基本MVC：这是什么＆QUOT; modelItem =＆GT;＆QUOT;做？ [英] Basic MVC: What does "modelItem =>" do?

问题描述

下面是一个经常由Visual Studio在MVC类型的应用程序产生code的样本行：

Here is a sample line of code that is often generated by Visual Studio in an MVC type of application:

@Html.DisplayFor(modelItem => item.LastName) 

• 我了解剃刀工程（即 @ ）


• 我理解HTML是静态辅助功能，如 DisplayFor（）
对象

• 我理解 item.LastName ，因为这松散的重新presents从数据/模型行和列


• I understand how razor works (the @)
• I understand Html is an object with static helper functions, like DisplayFor()
• I understand item.LastName as this loosely represents a row and column from data/model

...但到底是什么 modelItem =＆GT; ？早在我的一天， =＆GT; 曾经是被评价为一个布尔值的运营商。这是什么魔法？

...but what the heck is modelItem =>? Back in my day, => used to be an operator that was evaluated to a Boolean value. What is this sorcery?

推荐答案

你在做什么有一个路过的lambda前pression。这些都是基本相同的代表，函数指针在C或函数在Javascript中。 Youare基本上是告诉的Html DisplayFor使用此函数来获取显示项目。您的示例实际上应该可能是：

What you are doing there is passing a lambda expression. These are essentially the same as delegates, function pointers in C or functions in Javascript. Youare basically telling Html DisplayFor "use this function to get the display item". Your example should actually probably be:

@Html.DisplayFor(modelItem => modelItem.LastName)

否则，你正试图从外部范围关闭项。如果这是你真正想要做什么，然后modelItem基本上无所事事...

Otherwise, you are trying to close "item" from an outer scope. If this is what you are really trying to do, then modelItem is doing essentially nothing...

看<一个href=\"http://msdn.microsoft.com/en-us/library/bb397687.aspx\">http://msdn.microsoft.com/en-us/library/bb397687.aspx

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