By default, the Razor SDK doesn't publish reference assemblies that are required to perform runtime compilation. This results in compilation failures when the application model relies on runtime compilation—for example, the app uses embedded views or changes views after the app is published. Set CopyRefAssembliesToPublishDirectory to true to continue publishing reference assemblies. Both code generation and compilation are supported by a single call to the compiler. A single assembly is produced that contains the app types and the generated views.

For a web app, ensure your app is targeting the Microsoft.NET.Sdk.Web SDK.

Razor language version

When targeting the Microsoft.NET.Sdk.Web SDK, the Razor language version is inferred from the app's target framework version. For projects targeting the Microsoft.NET.Sdk.Razor SDK or in the rare case that the app requires a different Razor language version than the inferred value, a version can be configured by setting the <RazorLangVersion> property in the app's project file:

<PropertyGroup>
  <RazorLangVersion>{VERSION}</RazorLangVersion>
</PropertyGroup>
Razor's language version is tightly integrated with the version of the runtime that it was built for. Targeting a language version that isn't designed for the runtime is unsupported and likely produces build errors.
Additional resources
Additions to the csproj format for .NET Core
Common MSBuild project items
The .NET Core 2.1 SDK or later includes the Microsoft.NET.Sdk.Razor MSBuild SDK (Razor SDK). The Razor SDK:
Is required to build, package, and publish projects containing Razor files for ASP.NET Core MVC-based or Blazor projects.
Includes a set of predefined targets, properties, and items that allow customizing the compilation of Razor (.cshtml or .razor) files.
The Razor SDK includes Content items with Include attributes set to the **\*.cshtml and **\*.razor globbing patterns. Matching files are published.
Prerequisites
.NET Core 2.1 SDK or later
Use the Razor SDK
Most web apps aren't required to explicitly reference the Razor SDK.
To use the Razor SDK to build class libraries containing Razor views or Razor Pages, we recommend starting with the Razor class library (RCL) project template. An RCL that's used to build Blazor (.razor) files minimally requires a reference to the Microsoft.AspNetCore.Components package. An RCL that's used to build Razor views or pages (.cshtml files) minimally requires targeting netcoreapp3.0 or later and has a FrameworkReference to the Microsoft.AspNetCore.App metapackage in its project file.
Properties
The following properties control the Razor's SDK behavior as part of a project build:
RazorCompileOnBuild: When true, compiles and emits the Razor assembly as part of building the project. Defaults to true.
RazorCompileOnPublish: When true, compiles and emits the Razor assembly as part of publishing the project. Defaults to true.
The properties and items in the following table are used to configure inputs and output to the Razor SDK.
Warning
Starting with ASP.NET Core 3.0, MVC Views or Razor Pages aren't served by default if the RazorCompileOnBuild or RazorCompileOnPublish MSBuild properties in the project file are disabled. Applications must add an explicit reference to the Microsoft.AspNetCore.Mvc.Razor.RuntimeCompilation package if the app relies on runtime compilation to process .cshtml files.
RazorComponent
Item elements (.razor files) that are inputs to Razor component code generation.
RazorCompile
Item elements (.cs files) that are inputs to Razor compilation targets. Use this ItemGroup to specify additional files to be compiled into the Razor assembly.
RazorTargetAssemblyAttribute
Item elements used to code generate attributes for the Razor assembly. For example:  
RazorAssemblyAttribute
Include="System.Reflection.AssemblyMetadataAttribute"
_Parameter1="BuildSource" _Parameter2="https://learn.microsoft.com/">
RazorEmbeddedResource
Item elements added as embedded resources to the generated Razor assembly.
RazorCompileToolset
Used to determine the toolset used to build the Razor assembly. Valid values are Implicit, RazorSDK, and PrecompilationTool.
EnableDefaultContentItems
Default is true. When true, includes web.config, .json, and .cshtml files as content in the project. When referenced via Microsoft.NET.Sdk.Web, files under wwwroot and config files are also included.
EnableDefaultRazorGenerateItems
When true, includes .cshtml files from Content items in RazorGenerate items.
GenerateRazorTargetAssemblyInfo
When true, generates a .cs file containing attributes specified by RazorAssemblyAttribute and includes the file in the compile output.
EnableDefaultRazorTargetAssemblyInfoAttributes
When true, adds a default set of assembly attributes to RazorAssemblyAttribute.
CopyRazorGenerateFilesToPublishDirectory
When true, copies RazorGenerate items (.cshtml) files to the publish directory. Typically, Razor files aren't required for a published app if they participate in compilation at build-time or publish-time. Defaults to false.
PreserveCompilationReferences
When true, copy reference assembly items to the publish directory. Typically, reference assemblies aren't required for a published app if Razor compilation occurs at build-time or publish-time. Set to true if your published app requires runtime compilation. For example, set the value to true if the app modifies .cshtml files at runtime or uses embedded views. Defaults to false.
IncludeRazorContentInPack
When true, all Razor content items (.cshtml files) are marked for inclusion in the generated NuGet package. Defaults to false.
EmbedRazorGenerateSources
When true, adds RazorGenerate (.cshtml) items as embedded files to the generated Razor assembly. Defaults to false.
UseRazorBuildServer
When true, uses a persistent build server process to offload code generation work. Defaults to the value of UseSharedCompilation.
GenerateMvcApplicationPartsAssemblyAttributes
When true, the SDK generates additional attributes used by MVC at runtime to perform application part discovery.
DefaultWebContentItemExcludes
A globbing pattern for item elements that are to be excluded from the Content item group in projects targeting the Web or Razor SDK
ExcludeConfigFilesFromBuildOutput
When true, .config and .json files do not get copied to the build output directory.
AddRazorSupportForMvc
When true, configures the Razor SDK to add support for the MVC configuration that is required when building applications containing MVC views or Razor Pages. This property is implicitly set for .NET Core 3.0 or later projects targeting the Web SDK
RazorLangVersion
The version of the Razor Language to target.
For more information on properties, see MSBuild properties.
Targets
The Razor SDK defines two primary targets:
RazorGenerate: Code generates .cs files from RazorGenerate item elements. Use the RazorGenerateDependsOn property to specify additional targets that can run before or after this target.
RazorCompile: Compiles generated .cs files in to a Razor assembly. Use the RazorCompileDependsOn to specify additional targets that can run before or after this target.
RazorComponentGenerate: Code generates .cs files for RazorComponent item elements. Use the RazorComponentGenerateDependsOn property to specify additional targets that can run before or after this target.
Runtime compilation of Razor views
By default, the Razor SDK doesn't publish reference assemblies that are required to perform runtime compilation. This results in compilation failures when the application model relies on runtime compilation—for example, the app uses embedded views or changes views after the app is published. Set CopyRefAssembliesToPublishDirectory to true to continue publishing reference assemblies.
For a web app, ensure your app is targeting the Microsoft.NET.Sdk.Web SDK.
Razor language version
When targeting the Microsoft.NET.Sdk.Web SDK, the Razor language version is inferred from the app's target framework version. For projects targeting the Microsoft.NET.Sdk.Razor SDK or in the rare case that the app requires a different Razor language version than the inferred value, a version can be configured by setting the <RazorLangVersion> property in the app's project file:
<PropertyGroup>
  <RazorLangVersion>{VERSION}</RazorLangVersion>
</PropertyGroup>
Razor's language version is tightly integrated with the version of the runtime that it was built for. Targeting a language version that isn't designed for the runtime is unsupported and likely produces build errors.
Additional resources
Additions to the csproj format for .NET Core
Common MSBuild project items
Standardizes the experience around building, packaging, and publishing projects containing Razor files for ASP.NET Core MVC-based projects.
Includes a set of predefined targets, properties, and items that allow customizing the compilation of Razor files.
The Razor SDK includes a Content item with an Include attribute set to the **\*.cshtml globbing pattern. Matching files are published.
Prerequisites
.NET Core 2.1 SDK or later
Use the Razor SDK
Most web apps aren't required to explicitly reference the Razor SDK.
To use the Razor SDK to build class libraries containing Razor views or Razor Pages:
Use Microsoft.NET.Sdk.Razor instead of Microsoft.NET.Sdk:
<Project SDK="Microsoft.NET.Sdk.Razor">
  <!-- omitted for brevity -->
</Project>
Typically, a package reference to Microsoft.AspNetCore.Mvc is required to receive additional dependencies that are required to build and compile Razor Pages and Razor views. At a minimum, your project should add package references to:
Microsoft.AspNetCore.Razor.Design
Microsoft.AspNetCore.Mvc.Razor.Extensions
Microsoft.AspNetCore.Mvc.Razor
The Microsoft.AspNetCore.Razor.Design package provides the Razor compilation tasks and targets for the project.
The preceding packages are included in Microsoft.AspNetCore.Mvc. The following markup shows a project file that uses the Razor SDK to build Razor files for an ASP.NET Core Razor Pages app:
<Project Sdk="Microsoft.NET.Sdk.Razor">
  <PropertyGroup>
    <TargetFramework>netcoreapp2.1</TargetFramework>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="Microsoft.AspNetCore.Mvc" Version="2.1.3" />
  </ItemGroup>
</Project>
Warning
The Microsoft.AspNetCore.Razor.Design and Microsoft.AspNetCore.Mvc.Razor.Extensions packages are included in the Microsoft.AspNetCore.App metapackage. However, the version-less Microsoft.AspNetCore.App package reference provides a metapackage to the app that doesn't include the latest version of Microsoft.AspNetCore.Razor.Design. Projects must reference a consistent version of Microsoft.AspNetCore.Razor.Design (or Microsoft.AspNetCore.Mvc) so that the latest build-time fixes for Razor are included. For more information, see this GitHub issue.
Properties
The following properties control the Razor's SDK behavior as part of a project build:
RazorCompileOnBuild: When true, compiles and emits the Razor assembly as part of building the project. Defaults to true.
RazorCompileOnPublish: When true, compiles and emits the Razor assembly as part of publishing the project. Defaults to true.
The properties and items in the following table are used to configure inputs and output to the Razor SDK.
Items
Description
RazorComponent
Item elements (.razor files) that are inputs to Razor component code generation.
RazorCompile
Item elements (.cs files) that are inputs to Razor compilation targets. Use this ItemGroup to specify additional files to be compiled into the Razor assembly.
RazorTargetAssemblyAttribute
Item elements used to code generate attributes for the Razor assembly. For example:  
RazorAssemblyAttribute
Include="System.Reflection.AssemblyMetadataAttribute"
_Parameter1="BuildSource" _Parameter2="https://learn.microsoft.com/">
RazorEmbeddedResource
Item elements added as embedded resources to the generated Razor assembly.
RazorCompileToolset
Used to determine the toolset used to build the Razor assembly. Valid values are Implicit, RazorSDK, and PrecompilationTool.
EnableDefaultContentItems
Default is true. When true, includes web.config, .json, and .cshtml files as content in the project. When referenced via Microsoft.NET.Sdk.Web, files under wwwroot and config files are also included.
EnableDefaultRazorGenerateItems
When true, includes .cshtml files from Content items in RazorGenerate items.
GenerateRazorTargetAssemblyInfo
When true, generates a .cs file containing attributes specified by RazorAssemblyAttribute and includes the file in the compile output.
EnableDefaultRazorTargetAssemblyInfoAttributes
When true, adds a default set of assembly attributes to RazorAssemblyAttribute.
CopyRazorGenerateFilesToPublishDirectory
When true, copies RazorGenerate items (.cshtml) files to the publish directory. Typically, Razor files aren't required for a published app if they participate in compilation at build-time or publish-time. Defaults to false.
CopyRefAssembliesToPublishDirectory
When true, copy reference assembly items to the publish directory. Typically, reference assemblies aren't required for a published app if Razor compilation occurs at build-time or publish-time. Set to true if your published app requires runtime compilation. For example, set the value to true if the app modifies .cshtml files at runtime or uses embedded views. Defaults to false.
IncludeRazorContentInPack
When true, all Razor content items (.cshtml files) are marked for inclusion in the generated NuGet package. Defaults to false.
EmbedRazorGenerateSources
When true, adds RazorGenerate (.cshtml) items as embedded files to the generated Razor assembly. Defaults to false.
UseRazorBuildServer
When true, uses a persistent build server process to offload code generation work. Defaults to the value of UseSharedCompilation.
GenerateMvcApplicationPartsAssemblyAttributes
When true, the SDK generates additional attributes used by MVC at runtime to perform application part discovery.
DefaultWebContentItemExcludes
A globbing pattern for item elements that are to be excluded from the Content item group in projects targeting the Web or Razor SDK
ExcludeConfigFilesFromBuildOutput
When true, .config and .json files do not get copied to the build output directory.
AddRazorSupportForMvc
When true, configures the Razor SDK to add support for the MVC configuration that is required when building applications containing MVC views or Razor Pages. This property is implicitly set for .NET Core 3.0 or later projects targeting the Web SDK
RazorLangVersion
The version of the Razor Language to target.
For more information on properties, see MSBuild properties.
Targets
The Razor SDK defines two primary targets:
RazorGenerate: Code generates .cs files from RazorGenerate item elements. Use the RazorGenerateDependsOn property to specify additional targets that can run before or after this target.
RazorCompile: Compiles generated .cs files in to a Razor assembly. Use the RazorCompileDependsOn to specify additional targets that can run before or after this target.
RazorComponentGenerate: Code generates .cs files for RazorComponent item elements. Use the RazorComponentGenerateDependsOn property to specify additional targets that can run before or after this target.
Runtime compilation of Razor views
By default, the Razor SDK doesn't publish reference assemblies that are required to perform runtime compilation. This results in compilation failures when the application model relies on runtime compilation—for example, the app uses embedded views or changes views after the app is published. Set CopyRefAssembliesToPublishDirectory to true to continue publishing reference assemblies.
For a web app, ensure your app is targeting the Microsoft.NET.Sdk.Web SDK.
Razor language version
When targeting the Microsoft.NET.Sdk.Web SDK, the Razor language version is inferred from the app's target framework version. For projects targeting the Microsoft.NET.Sdk.Razor SDK or in the rare case that the app requires a different Razor language version than the inferred value, a version can be configured by setting the <RazorLangVersion> property in the app's project file:
<PropertyGroup>
  <RazorLangVersion>{VERSION}</RazorLangVersion>
</PropertyGroup>
Razor's language version is tightly integrated with the version of the runtime that it was built for. Targeting a language version that isn't designed for the runtime is unsupported and likely produces build errors.
Additional resources
Additions to the csproj format for .NET Core
Common MSBuild project items