MSBuild RegEx assembly version

Trying to create an MSBuild task that outputs my code to a folder. Everything works except the regex. My code:

<Target Name="AfterBuild">
  <GetAssemblyIdentity AssemblyFiles="$(OutDir)$(TargetFileName)">
    <Output TaskParameter="Assemblies" ItemName="TheVersion" />
  </GetAssemblyIdentity>
  <PropertyGroup>
    <Pattern>(\d+)\.(\d+)\.(\d+)</Pattern>
    <In>%(TheVersion.Version)</In>
    <OutVersion>$([System.Text.RegularExpressions.Regex]::Match($(In), $(Pattern)))</OutVersion>
  </PropertyGroup>
  <ItemGroup>
    <OutputFiles Include="$(OutDir)*" Exclude="*.tmp" />
    <SolnFiles Include="$(SolutionDir)INDIVIDUAL.txt;$(SolutionDir)LICENSE.txt;$(SolutionDir)README.md" />
  </ItemGroup>

  <Copy SourceFiles="@(OutputFiles)" DestinationFolder="$(SolutionDir)dache-%(OutVersion)\Tests" SkipUnchangedFiles="true" />
  <Copy SourceFiles="@(SolnFiles)" DestinationFolder="$(SolutionDir)dache-%(OutVersion)\" SkipUnchangedFiles="true" />
</Target>

      

        
        
        
      

    

When I run this I get this error:

The "D: \ Dache \ INDIVIDUAL.txt" item in the "SolnFiles" item list does not define a value for the "OutVersion" metadata. To use this metadata, either qualify it by specifying% (SolnFiles.OutVersion), or make sure that all the items in this list define a value for this metadata.

When I try %(SolnFiles.OutVersion)

it goes blank. I am doing something dumb here, what is it?