How can you conditionally run an MSBuild task only when your project outputs have been built?

Question

I want to run an MSBuild Task (which signs an executable/dll) but only when the output exe/dll has changed. If none of the source files have changed causing a recompile of the exe/dll then I don't want the task to run.

Despite spending several hours trying different things out I cannot work out how to get my target task to only run if the project has been compiled where the output files have changed (in other words the CoreCompile target was not skipped I think).

Answer 1

Should be the same as this answer, using the TargetOutputs parameter::

<MSBuild Projects="File.sln" >
   <Output TaskParameter="TargetOutputs" ItemName="AssembliesBuiltByChildProjects" />
</MSBuild>
<Message Text="Assemblies built: @(AssembliesBuiltByChildProjects)" /> <!-- just for debug -->
<CallTarget Targets="SignExe" Condition="'@(AssembliesBuiltByChildProjects)'!=''" />