Setting properties' values in MSBuild

Question

Let's consider the below example.

There, I have:

1. target MAIN calls target t and then calls target tt.
2. target t calls target ttt, and target tt calls target tttt.
3. target t defines property aa, and target ttt modifies aa.
4. target tttt tries to print property aa's value.
5. In short, we have: MAIN -> {t -> {ttt->modifies aa, defines aa}, tt -> tttt -> prints aa}

But in target tttt, we can't "see" aa's updated value (by ttt)! How do I make that value visible to target tttt?

The whole script is as below:

<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003" DefaultTargets="MAIN" >
  <Target Name="MAIN" >
    <CallTarget Targets="t" />
    <CallTarget Targets="tt" />
  </Target>

  <Target Name="t">
    <Message Text="t" />
    <PropertyGroup>
      <aa>1</aa>
    </PropertyGroup>
    <CallTarget Targets="ttt" />
  </Target>

  <Target Name="tt">
    <Message Text="tt" />
    <CallTarget Targets="tttt" />
  </Target>

  <Target Name="ttt">
    <PropertyGroup>
      <aa>122</aa>
    </PropertyGroup>
    <Message Text="ttt" />
  </Target>

  <Target Name="tttt">
    <Message Text="tttt" />
    <Message Text="tttt:$(aa)" />
  </Target>

</Project>

Answer 1

As already said in an answer to another post you should model your MSBuild project with dependencies between your Targets rather than calling Targets one after another.

<Project DefaultTargets="tttt" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
    <Target Name="t">
        <Message Text="t" />
            <PropertyGroup>
                <aa>1</aa>
            </PropertyGroup>
     </Target>

     <Target Name="tt" DependsOnTargets="t">
         <Message Text="tt" />
     </Target>

     <Target Name="ttt" DependsOnTargets="t;tt">
         <PropertyGroup>
             <aa>122</aa>
         </PropertyGroup>
         <Message Text="ttt" />
     </Target>

     <Target Name="tttt" DependsOnTargets="t;tt;ttt">
         <Message Text="tttt" />
         <Message Text="tttt:$(aa)" />
     </Target>
</Project>

An approach I use, is to define a Target as my final goal, putting it into the projects DefaultTargets.

Then add all the things that need to happen to achieve this goal.