What are the various "Build action" settings in Visual Studio project properties and what do they do?

• None: The file is not included in the project output group and is not compiled in the build process. An example is a text file that contains documentation, such as a Readme file.

• Compile: The file is compiled into the build output. This setting is used for code files.

• Content: Allows you to retrieve a file (in the same directory as the assembly) as a stream via Application.GetContentStream(URI). For this method to work, it needs a AssemblyAssociatedContentFile custom attribute which Visual Studio graciously adds when you mark a file as "Content"

• Embedded resource: Embeds the file in an exclusive assembly manifest resource.

• Resource (WPF only): Embeds the file in a shared (by all files in the assembly with similar setting) assembly manifest resource named AppName.g.resources.

• Page (WPF only): Used to compile a xaml file into baml. The baml is then embedded with the same technique as Resource (i.e. available as `AppName.g.resources)

• ApplicationDefinition (WPF only): Mark the XAML/class file that defines your application. You specify the code-behind with the x:Class="Namespace.ClassName" and set the startup form/page with StartupUri="Window1.xaml"

• SplashScreen (WPF only): An image that is marked as SplashScreen is shown automatically when an WPF application loads, and then fades

• DesignData: Compiles XAML viewmodels so that usercontrols can be previewed with sample data in Visual Studio (uses mock types)

• DesignDataWithDesignTimeCreatableTypes: Compiles XAML viewmodels so that usercontrols can be previewed with sample data in Visual Studio (uses actual types)

• EntityDeploy: (Entity Framework): used to deploy the Entity Framework artifacts

• CodeAnalysisDictionary: An XML file containing custom word dictionary for spelling rules

From the documentation:

The BuildAction property indicates what Visual Studio does with a file when a build is executed. BuildAction can have one of several values:

None - The file is not included in the project output group and is not compiled in the build process. An example is a text file that contains documentation, such as a Readme file.

Compile - The file is compiled into the build output. This setting is used for code files.

Content - The file is not compiled, but is included in the Content output group. For example, this setting is the default value for an .htm or other kind of Web file.

Embedded Resource - This file is embedded in the main project build output as a DLL or executable. It is typically used for resource files.

Page -- Takes the specified XAML file, and compiles into BAML, and embeds that output into the managed resource stream for your assembly (specifically AssemblyName.g.resources), Additionally, if you have the appropriate attributes on the root XAML element in the file, it will create a blah.g.cs file, which will contain a partial class of the "codebehind" for that page; this basically involves a call to the BAML goop to re-hydrate the file into memory, and to set any of the member variables of your class to the now-created items (e.g. if you put x:Name="foo" on an item, you'll be able to do this.foo.Background = Purple; or similar.

ApplicationDefinition -- similar to Page, except it goes onestep furthur, and defines the entry point for your application that will instantiate your app object, call run on it, which will then instantiate the type set by the StartupUri property, and will give your mainwindow.

Also, to be clear, this question overall is infinate in it's results set; anyone can define additional BuildActions just by building an MSBuild Task. If you look in the %systemroot%\Microsoft.net\framework\v{version}\ directory, and look at the Microsoft.Common.targets file, you should be able to decipher many more (example, with VS Pro and above, there is a "Shadow" action that allows you generate private accessors to help with unit testing private classes.

In VS2008, the doc entry that seems the most useful is:

Windows Presentation Foundation Building a WPF Application (WPF)

ms-help://MS.VSCC.v90/MS.MSDNQTR.v90.en/wpf_conceptual/html/a58696fd-bdad-4b55-9759-136dfdf8b91c.htm

ApplicationDefinition Identifies the XAML markup file that contains the application definition (a XAML markup file whose root element is Application). ApplicationDefinition is mandatory when Install is true and OutputType is winexe. A WPF application and, consequently, an MSBuild project can only have one ApplicationDefinition.

Page Identifies a XAML markup file whose content is converted to a binary format and compiled into an assembly. Page items are typically implemented in conjunction with a code-behind class.

The most common Page items are XAML files whose top-level elements are one of the following:

Window (System.Windows..::.Window).

Page (System.Windows.Controls..::.Page).

PageFunction (System.Windows.Navigation..::.PageFunction<(Of <(T>)>)).

ResourceDictionary (System.Windows..::.ResourceDictionary).

FlowDocument (System.Windows.Documents..::.FlowDocument).

UserControl (System.Windows.Controls..::.UserControl).

Resource Identifies a resource file that is compiled into an application assembly. As mentioned earlier, UICulture processes Resource items.

Content Identifies a content file that is distributed with an application. Metadata that describes the content file is compiled into the application (using AssemblyAssociatedContentFileAttribute).

Build actions control the MSBuild Item Type of each item in a project. For example, a Compile build action on MyClass.cs means something like this in your .csproj file:

<ItemGroup>
  <Compile>MyClass.cs</Compile>
</ItemGroup>

Item types have specific meanings by convention. Common types are Compile, Content and None, but there are others.

For example, .editorconfig files have their own item type (EditorConfigFiles). Files may be passed to analyzers by marking them with "C# analyzer additional file" (AdditionalFiles).

You can also define your own item types in your project for your own purposes via AvailableItemName. For example:

<ItemGroup>
  <AvailableItemName Include="Foo" />
</ItemGroup>

Doing this will produce: