在源代码中查找这些信息比在文档中查找要好得多。

参考来自Github的MVC 6代码，我们有一些感兴趣的文件

——更新

由于源结构的变化，关于如何收集视图开始页的信息现在可以在RazorViewEngine.cs寻找“GetViewStartPages”函数中找到。

——/更新

为了回答它们是如何发挥作用的，看看RazorView，我相信(因为IView)它是绑定在MVC管道中的。这个文件有一个RenderAsync方法，可以从MVC管道中调用来呈现所请求的视图。

RenderAsync调用RenderPage和RenderLayout(注意顺序)。 RenderPage首先调用viewstart文件(注意复数，可能有多个_viewstart文件)。

所以，你所寻找的信息可以从Microsoft.AspNet.Mvc.Razor命名空间下RazorView.cs文件中的RenderViewStartAsync函数中获得。

来自ScottGu的博客:

Starting with the ASP.NET MVC 3 Beta release, you can now add a file called _ViewStart.cshtml (or _ViewStart.vbhtml for VB) underneath the \Views folder of your project: The _ViewStart file can be used to define common view code that you want to execute at the start of each View’s rendering. For example, we could write code within our _ViewStart.cshtml file to programmatically set the Layout property for each View to be the SiteLayout.cshtml file by default: Because this code executes at the start of each View, we no longer need to explicitly set the Layout in any of our individual view files (except if we wanted to override the default value above). Important: Because the _ViewStart.cshtml allows us to write code, we can optionally make our Layout selection logic richer than just a basic property set. For example: we could vary the Layout template that we use depending on what type of device is accessing the site – and have a phone or tablet optimized layout for those devices, and a desktop optimized layout for PCs/Laptops. Or if we were building a CMS system or common shared app that is used across multiple customers we could select different layouts to use depending on the customer (or their role) when accessing the site. This enables a lot of UI flexibility. It also allows you to more easily write view logic once, and avoid repeating it in multiple places.

还有这个。

If you want to have a common layout for your pages you need to define the common layout and to associate a view with layout we have to set layout property on each and every view, this violates the DRY(Don't Repeat Yourself) principle. For this .Net Framework has provide the "_ViewStart.cshtml" file, placed inside the view folder. We place layout information in "_ViewStart.cshtml" file and every view by default uses this layout information. If you want to give some different layout information, lets suppose to your Home view, you can create a new "_ViewStart.cshtml" with reference to that layout and place it in the "Home View" folder.

这可能会为这个问题增加一些附加信息(2016 ala MVC4, MVC5)。

Razor引擎找到并运行_ViewStart中的代码。cshtml在任何其他代码之前，这些代码位于_ViewStart. xml所在的同一目录或子目录中。找到CSHTML。

任何视图都可以覆盖Layout属性或其任何值。

只是想我可能会添加一些信息来告诉你为什么它是_ViewStart。

如果您获得ILSpy并检查RazorViewEngine (System.Web.Mvc.dll)中的代码，您将看到代码本身引用了该名称。

你可以看到RazorViewEngine在寻找这个名称的文件:

RazorViewEngine.ViewStartFileName = "_ViewStart";

只是另一个想法。

如果您想拥有自己的cshtml文件作为公共模板，可以采用这种方式

在你的_viewstart。你可以提到你常用的CSHTML文件。

@{Layout = "~/Views/Shared/_Layout.cshtml";}

在更普遍的意义上，MVC框架“知道”_Viewstart的能力。cshtml被称为“按惯例编码”。

Convention over configuration (also known as coding by convention) is a software design paradigm which seeks to decrease the number of decisions that developers need to make, gaining simplicity, but not necessarily losing flexibility. The phrase essentially means a developer only needs to specify unconventional aspects of the application. For example, if there's a class Sale in the model, the corresponding table in the database is called “sales” by default. It is only if one deviates from this convention, such as calling the table “products_sold”, that one needs to write code regarding these names.

维基百科

没有什么神奇的。它只是被写进MVC框架的核心代码库，因此是MVC“知道”的东西。这就是为什么你在.config文件或其他地方找不到它;它实际上在MVC代码中。但是，您可以重写以更改或取消这些约定。