MSBuild Filtering ItemGroup of files with condition

Question

This feels like it\'s so simple, but I cannot get it to work.

All I\'m trying to achieve is a filtered list of the embedded resources. I\'ve tried various approaches bu

Answer 1

Inside a target, this can be done using the batching syntax for items and using the System.String.Copy method to be able to call instance functions on the string:

<Target Name="ListAllEmbeddedResources">
  <ItemGroup>
    <AllEmbeddedResources Include="@(EmbeddedResource)" Condition="$([System.String]::Copy(%(FullPath)).Contains('Change'))" />
  </ItemGroup>
  <Message Importance="high" Text="AllEmbeddedResources: %(AllEmbeddedResources.Identity)" />
</Target>

Note that this syntax only works inside a target and not during static evaluation (item group directly under the <Project> node).

Answer 2

The Condition Attribute must return a boolean, and it operates on each element of the itemgroup. You can access each element using %(Identity). Say you have some unfiltered itemgroup called UnfilteredItems, and you want to filter those into a group called MyFilteredItems, using some regex pattern.

<ItemGroup>
  <MyFilteredItems Include="@(UnfilteredItems)" Condition="$([System.Text.RegularExpressions.Regex]::Match(%(Identity),'.*\\bin\\.*').Success)"/>
</ItemGroup>