A couple of months ago I wrote a blog post MSBuild how to execute a target after CoreCompile in which I describe how you can execute a target if the CoreCompile target is executed, if CoreCompile is skipped then so will your other target. The draw back of the approach that I outlined in my previous post was that it required you to edit your .csproj/.vbproj/etc file itself. So if you had a scenario where you were building multiple projects then you would have to edit all of the project files. In this post I’ll describe how you can perform the same customization without having to edit the project file itself. Note this blog is in response to a question on StackOverflow Determine if MSBuild CoreCompile will run and call custom target.

Before we get to the solution for this particular case let me describe an extensibility hook that the C# and VB projects have. Most of the logic for building C# and VB projects is captured in the MSBuild targets file at C:\Windows\Microsoft.NET\Framework\v4.0.30319\Microsoft.Common.targets. If you take a look in that file you will notice at the top an import looking like the one below.

This statement will import a file (located at the value for CustomBeforeMicrosoftCommonTargets) if the property is not empty and the file exists. The default value for CustomBeforeMicrosoftCommonTargets is C:\Program Files (x86)\MSBuild\v4.0\Custom.Before.Microsoft.Common.targets. So if you drop an MSBuild file at that location it will modify the build process for every C#/VB project built on that machine. Alternatively if you do not want (or cannot due to ACLs) then you can drop the file somewhere else and then specify its location by overriding the CustomBeforeMicrosoftCommonTargets property. This is the approach that I will take here. I have created a sample solution which consists of two projects ProjA and ProjB. I also have a build script, build.proj, to automate the build for this. Below is the entire contents of build.proj.

build.proj

  
    $(MSBuildThisFileDirectory)extend-corecompile.proj
  

  
    
    
  

  
       
  

  
    
  

  
  

In the Build target above I use the MSBuild task to build both ProjA and ProjB. As you can see I am passing the property CustomBeforeMicrosoftCommonTargets=$(FileToInject) which points to extend-corecompile.proj. By passing this property when ProjA, and ProjB, is built it will automatically import the extend-corecompile.proj file for the build process. You can see the contents of extend-corecompile.proj below.

extend-corecompile.proj

  
    
      $(TargetsTriggeredByCompilation);
      MyCustomTarget
    
  

  
    
  
  

This project file uses the technique outlined in my previous blog post to execute the MyCustomTarget only if CoreCompile is executed.

Note: You can get the latest version of this sample at https://github.com/sayedihashimi/sayed-samples/tree/master/ExtBuildMultiple.

Sayed Ibrahim Hashimi | SayedIHashimi