Why are the C# pre-build and post-build events not called if I import a custom target with my own build target in it?

Question

Why are the C# pre-build and post-build events not called if I import a custom target with my own build target in it?

I have a C# project file, which I modified by importing my own custom target file. Inside the target, I have defined a "Build" target which will be called when I do the build from the Visual Studio IDE or from the MSBUILD command line.

<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
    <Target Name="Build"> 
        <Message Text="Custom Build started" Importance="high"/>
    </Target>
</Project>

The "Build" target from the custom target file is getting called if I do the build from the Visual Studio IDE or from the MSBUILD command line. But, the pre-build and post-build events configured inside the project file is not getting called after importing my own custom target file.

It will be great if anybody could suggest what kind of change I have to make in my target file to call the pre-build event before calling the "Build" target from my target file, and the post-build event after the "Build" target.

Answer 1

Your custom Build target is overriding the project system provided Build target.

As of the time of writing this answer, the project system Build is defined as follows:

  <!--
    ============================================================
                                        Build

    The main build entry point.
    ============================================================
    -->
  <PropertyGroup>
    <BuildDependsOn>
      BeforeBuild;
      CoreBuild;
      AfterBuild
    </BuildDependsOn>
  </PropertyGroup>

  <Target
      Name="Build"
      Condition=" '$(_InvalidConfigurationWarning)' != 'true' "
      DependsOnTargets="$(BuildDependsOn)"
      Returns="@(TargetPathWithTargetPlatformMoniker)" />

The definition of the CoreBuild target is where the PreBuildEvent and PostBuildEvent targets are introduced to the target chain.

As of the time of writing this answer, CoreBuild is defined as follows:

  <!--
    ============================================================
                                        CoreBuild

    The core build step calls each of the build targets.
    ============================================================
    -->
  <PropertyGroup>
    <CoreBuildDependsOn>
      BuildOnlySettings;
      PrepareForBuild;
      PreBuildEvent;
      ResolveReferences;
      PrepareResources;
      ResolveKeySource;
      Compile;
      ExportWindowsMDFile;
      UnmanagedUnregistration;
      GenerateSerializationAssemblies;
      CreateSatelliteAssemblies;
      GenerateManifests;
      GetTargetPath;
      PrepareForRun;
      UnmanagedRegistration;
      IncrementalClean;
      PostBuildEvent
    </CoreBuildDependsOn>
  </PropertyGroup>

  <Target
      Name="CoreBuild"
      DependsOnTargets="$(CoreBuildDependsOn)">

    <OnError ExecuteTargets="_TimeStampAfterCompile;PostBuildEvent" Condition="'$(RunPostBuildEvent)'=='Always' or '$(RunPostBuildEvent)'=='OnOutputUpdated'"/>
    <OnError ExecuteTargets="_CleanRecordFileWrites"/>

  </Target>

Because you override Build and your override doesn't have DependsOnTargets="$(BuildDependsOn)", CoreBuild is not in the target chain. Then because CoreBuild is not in the target chain, its dependencies, including PreBuildEvent and PostBuildEvent, are not in the target chain.

You could change your custom build to something like the following which sets a target chain that includes PreBuildEvent and PostBuildEvent.

    <Target Name="Build" DependsOnTargets="PreBuildEvent;CustomBuild;PostBuildEvent"/>
    <Target Name="CustomBuild">
        <Message Text="Custom Build started" Importance="high"/>
    </Target>

If what you actually need is a "utility" project that doesn't actually build, see the "Microsoft.Build.NoTargets" project SDK.