Compile MVC views during build

By default views are compiled at the runtime on the first request. It slows down start up times but also if there is a bug in the view, the error page will be displayed. That is why, it’s good idea to compile mvc views during build to pick up errors as early in the development process as possible.

Enabling MVC compilation during build time can be done by extending msbuild. To achive that paste the following code to the Directory.Build.targets file:

<PropertyGroup>
  <BuildDependsOn>
    $(BuildDependsOn);
    BuildMvcViews;
  </BuildDependsOn>
</PropertyGroup>

<Target Name="BuildMvcViews">
  <AspNetCompiler VirtualPath="temp" PhysicalPath="$(ProjectDir)" />
</Target>

Build MVC views incrementally

Above code works fine, however if you have huge number of projects (like we normally have in sitecore solutions) and a lot of *.cshtml files, the total build time of your solution can hugely increase. The aspnet_compiler.exe which is used under the hood is not well optimized. In my current project building mvc views doubles the total build time. It is especially painfull for those with slow machines.

MSBuild has a feature called incremental builds that can be used to tell msbuild to avoid building views again if there are no changes.

The quote from the documentation says:

To enable incremental builds (builds in which only those targets that have not been built before or targets that are out of date, are rebuilt), the Microsoft Build Engine (MSBuild) can compare the timestamps of the input files with the timestamps of the output files and determine whether to skip, build, or partially rebuild a target.

To use that feature we need to provide input files and output file(s) so MSBuild can compare timestamps of them. For inputs we can use *.cshtml files:

<ItemGroup>
  <BuildMvcViewsInputs Include="$(ProjectDir)Views\**\*.cshtml"></BuildMvcViewsInputs>
</ItemGroup>

We don’t have output file so we need to create one. For that we can just create an empty file and store it inside obj\$(Configuration). The file will be updated everytime the views are compiled. So the timestamp of the output file will be greater than timestamp of all the input files, unless any of the input files will be modified. In that case rebuild will happen again and output file will be overwritten with a new timestamp. We can keep the path to the output file in a new property:

<BuildMvcViewsCacheFile>$(IntermediateOutputPath)$(MSBuildProjectFile).BuildMvcViews.cache</BuildMvcViewsCacheFile>

We can generate that output file directly after the compilation of mvc views is completed by adding following code after <AspNetCompiler:

<WriteLinesToFile
    File="$(BuildMvcViewsCacheFile)"
    Lines=""
    Overwrite="true" />

Finally we can provide Inputs and Outputs to BuildMvcViews target and set Conditions. Complete code can looks like this:

<PropertyGroup>
  <BuildDependsOn>
    $(BuildDependsOn);
    BuildMvcViews;
  </BuildDependsOn>

  <BuildMvcViewsCacheFile>$(IntermediateOutputPath)$(MSBuildProjectFile).BuildMvcViews.cache</BuildMvcViewsCacheFile>
</PropertyGroup>

<ItemGroup>
  <BuildMvcViewsInputs Include="$(ProjectDir)Views\**\*.cshtml"></BuildMvcViewsInputs>
</ItemGroup>

<Target Name="BuildMvcViews" Inputs="@(BuildMvcViewsInputs)" Outputs="$(BuildMvcViewsCacheFile)">
  <AspNetCompiler VirtualPath="temp" PhysicalPath="$(ProjectDir)" Condition="'@(BuildMvcViewsInputs)' != ''"/>
  <WriteLinesToFile
    File="$(BuildMvcViewsCacheFile)"
    Lines=""
    Overwrite="true"
    Condition="'@(BuildMvcViewsInputs)' != ''"/>
</Target>

There is one more thing to do. We need to delete the output file when someones runs Cleanup or Rebuild of the solution. For that we need to update the code with the following code:

<PropertyGroup>
  <CleanDependsOn>
    $(CleanDependsOn);
    CleanBuildMvcViewsCacheFile;
  </CleanDependsOn>
</PropertyGroup>

<Target Name="CleanBuildMvcViewsCacheFile">
  <Delete Files="$(BuildMvcViewsCacheFile)" />
</Target>

The complete example looks like this:

<PropertyGroup>
  <BuildDependsOn>
    $(BuildDependsOn);
    BuildMvcViews;
  </BuildDependsOn>

  <BuildMvcViewsCacheFile>$(IntermediateOutputPath)$(MSBuildProjectFile).BuildMvcViews.cache</BuildMvcViewsCacheFile>
</PropertyGroup>

<ItemGroup>
  <BuildMvcViewsInputs Include="$(ProjectDir)Views\**\*.cshtml"></BuildMvcViewsInputs>
</ItemGroup>

<Target Name="BuildMvcViews" Inputs="@(BuildMvcViewsInputs)" Outputs="$(BuildMvcViewsCacheFile)">
  <AspNetCompiler VirtualPath="temp" PhysicalPath="$(ProjectDir)" Condition="'@(BuildMvcViewsInputs)' != ''"/>
  <WriteLinesToFile
    File="$(BuildMvcViewsCacheFile)"
    Lines=""
    Overwrite="true"
    Condition="'@(BuildMvcViewsInputs)' != ''"/>
</Target>

<PropertyGroup>
  <CleanDependsOn>
    $(CleanDependsOn);
    CleanBuildMvcViewsCacheFile;
  </CleanDependsOn>
</PropertyGroup>

<Target Name="CleanBuildMvcViewsCacheFile">
  <Delete Files="$(BuildMvcViewsCacheFile)" />
</Target>