title: Environment variables get lost between MSBuild projects
body: <p>I have a .NET solution containing following projects:</p>
  
  <ul>
  <li>web application (WAP)</li>
  <li>web deployment (WDP, .wdproj) </li>
  <li>wix setup (WIX, .wixproj)</li>
  </ul>
  
  <p>In the WDP I've used a custom MSBuild task (SetEnvVar) to set some env. variables for further use in the build process. After setting them I can use them without prob. 
  in the WDP but in the WIX they are empty/undefined. The strange thing is that when I reference those env. vars in the WIX files (by using properties in .wxs or preproc vars in .wxi) I get the values as expected.</p>
  
  <p>Do you have any idea why the env. vars get lost/are undefined in .wixproj?</p>
  
  <p>By the way the (solution) build process is triggered from inside VS 2010.</p>
  
  <p><strong>Update</strong></p>
  
  <p>This is basically my task code: </p>
  
  <pre><code>Environment.SetEnvironmentVariable(this.Variable, this.Value);
  </code></pre>
  
  <p>Is a MSBuild solution build not one process?</p>
  
  <p>Will MSBuild spawn a new process for every project in the solution?</p>