MSBuild How to pass same task to multiple projects

Question

I am wanting to run the same task on multiple projects from one build file without having to copy the task to each project file.

I am getting all project files in my solution and:

<ItemGroup>
    <ProjectsToBuild Include="..\Modules\**\*csproj"/>
</ItemGroup>

I am then calling the MSBuild task on each ProjectToBuild

<MSBuild Projects ="@(ProjectsToBuild)" 
             Targets="DoStuff"
             ContinueOnError ="false" 
             Properties="Configuration=$(Configuration)">
    <Output ItemName="OutputFiles" TaskParameter="TargetOutputs"/>
</MSBuild>

This doesn't work, as the Target must exist in the project you are building.

From MSDN

The targets must occur in all the project files. If they do not, a build error occurs.

Is there a way I can pass the DoStuff task to the projects that are being passed into the MSBuild task?

Answer 1

Since this project has a few different people from different timezones and locations, I didn't want to add another requirement for people to update their proj files manually everytime. I was able to do what I wanted in the end however.

<Target Name="BuildAll" DependsOnTargets="$(BuildAllDependsOn)"/>

<PropertyGroup>
    <BuildAllDependsOn>UpdateProjects;CoreBuild</BuildAllDependsOn>
</PropertyGroup>

<ItemGroup>
    <ProjectsToBuild Include="$(MSBuildProjectDirectory)\..\MyProjects\**\*csproj" Exclude="$(MSBuildProjectDirectory)\..\MyProjects\**\Team*csproj;$(MSBuildProjectDirectory)\..\MyProjects\**\Image*csproj"/>
</ItemGroup>

<Target Name="CoreBuild">
<Message Text="CoreBuild" />
    <MSBuild Projects ="@(ProjectsToBuild)" 
             Targets ="DoStuff" 
             ContinueOnError ="false" 
             Properties="Configuration=$(Configuration)">
        <Output ItemName="OutputFiles" TaskParameter="TargetOutputs"/>
    </MSBuild>
</Target>

<Target Name="UpdateProjects">
    <Message Text="$(MSBuildProjectDirectory)" />
    <ItemGroup>
      <CSProjects Include="$(MSBuildProjectDirectory)\..\MyProjects\**\*csproj" Exclude="$(MSBuildProjectDirectory)\..\MyProjects\**\Team*csproj;$(MSBuildProjectDirectory)\..\MyProjects\**\Image*csproj" />
    </ItemGroup>
    <Message Text="Updating Projects:[@(CSProjects)]" />
    <UpdateProject ProjectPath="%(CSProjects.Identity)" ImportsPath="$(MSBuildProjectDirectory)\projectImports.Targets" ModuleTargets="$(MSBuildProjectDirectory)\DoStuff.Targets" CommunityTasksPath="$(MSBuildProjectDirectory)" />
 </Target>

<UsingTask
  TaskName="UpdateProject"
  TaskFactory="CodeTaskFactory"
  AssemblyFile="$(MSBuildToolsPath)\Microsoft.Build.Tasks.v12.0.dll">
  <ParameterGroup>
      <ProjectPath Required="true" />
      <ImportsPath Required="true" />
      <ModuleTargets Required="true" />
      <CommunityTasksPath Required="true" />
  </ParameterGroup>
  <Task>
      <Reference Include="System.Xml" />
      <Reference Include="System.Xml.Linq" />
      <Using Namespace="System" />
      <Using Namespace="System.Linq" />
      <Using Namespace="System.Xml.Linq" />
      <Code Type="Fragment" Language="cs">
          <![CDATA[
              var document = XDocument.Load(ProjectPath);
              XNamespace ns = "http://schemas.microsoft.com/developer/msbuild/2003";
              var alreadyAdded = document.Descendants(ns + "Target").Any(el => (string)el.Attribute("DependsOnTargets").Value == "DoStuff");
              if (!alreadyAdded)
                  {
                      var importsDoc = XDocument.Load(ImportsPath);
                      importsDoc.Descendants(ns + "Import").FirstOrDefault().Attribute("Project").Value = ModuleTargets;
                      importsDoc.Descendants(ns + "MSBuildCommunityTasksPath").FirstOrDefault().Value = CommunityTasksPath;
                      document.Descendants(ns + "Project").FirstOrDefault().Add(importsDoc.Root.Elements());
                      document.Save(ProjectPath);
                  }
          ]]>
      </Code>
  </Task>
</UsingTask>

I first call UpdateProjects which updates each projects file with the location of the task. I use a code block (linq to xml) to find and update the project file. If it has already been updated, it won't add the same thing twice. I then call build on each project file and tell msbuild the name of the target that was added to each project file.