MsBuild Target Order

MsBuild version 4.0 introduced two new Target attributes: BeforeTargets and AfterTargets. Prior to v4.0 if you wanted to run some tasks before or after a target you had to explicitly build them into the dependency chain using the DependsOnTargets attribute. For example, if you wanted to do something like print a set of configuration messages before running a build, you had to add that target to the list of build dependencies.

    <Target Name="PrintBuildInfo" >
    	<Message
    		Text="This is a $(Configuration) build."
    		Importance="high"
    		/>
    	<Message
    		Text=".NET framework version $(TargetFrameworkVersion)"
    		/>
    </Target>

    <Target Name="Build"
    	DependsOnTargets="PrintBuildInfo" >

    	<!-- Build Stuff -->

    </Target>

I'm sure you will agree that printing the build info is not really something that Build depends on, at least not in the same way as cleaning a directory or making sure a file is in the right place.

This style of target chaining contributes to the fragility of builds and make it harder to build loosely coupled scripts, not to mention adding diagnostics during development.

With BeforeTargets the original DependsOnTargets list can stay the same, semantically representing the important parts of the build process and self-contained targets can be slotted into the process as required. Magic.

    <Target Name="PrintBuildInfor"
    	BeforeTargets="Build">
    	<Message
    		Text="This is a $(Configuration) build."
    		Importance="high"
    		/>
    	<Message
    		Text=".NET framework version $(TargetFrameworkVersion)"
    		/>
    </Target>

    <Target Name="Build" >

    	<!-- Build Stuff -->

    </Target>

One thing to note is adding BeforeTargets and AfterTargets changes how MsBuild derives the final build order of targets but the targets you define still only run once per build even if you specify more than one build target in the attribute.