An MSBuild target to add to your project files that will restore packages *if* nuget.exe is available via the PATH environment variable.

gistfile1.xml

  <!-- add this target to *each* project file, and modify the BeforeBuild target that's already in the project file (usually commented out) to depend on it -->
  <Target Name="RestoreNuGetPackages" Condition="Exists('.\packages.config')">
    <!-- try to execute `nuget help` to see if it's available from what's in the PATH -->
    <Exec Command="cmd.exe /c nuget help &gt; NUL" IgnoreExitCode="True">
      <Output TaskParameter="ExitCode" PropertyName="NuGetExitCode"/>
    </Exec>
    <!-- raise an error if nuget.exe wassn't available from what's in the PATH -->
    <Error Text="Failed to execute nuget.exe; please make sure your PATH environment variable provides a path to nuget.exe." Condition="'$(NuGetExitCode)' != '' and '$(NuGetExitCode)' > '0'" />
    <!-- restore packages -->
    <Exec Command="nuget install .\packages.config -o $(SolutionDir)\packages" />
  </Target>
  
  <!-- You might have to un-comment the BeforeBuild target before adding the DependsOnTargets="RestoreNuGetPackages" attribute -->
  <Target Name="BeforeBuild" DependsOnTargets="RestoreNuGetPackages"></Target>