MsBuild: Item: Remove with absolute path - msbuild

Question

This comes from a Shared project:
<Content Include="$(MSBuildThisFileDirectory)MyFile1" />
Let's say it's equivalent to
<Content Include="c:\MyProject\MyFile1" />
This comes from a normal project:
<Content Include="MyFile2" />
One is an absolute path, the other is a relative one.
Which makes issues when trying to Remove them, because eg the one with the relative path can't be Remove-d with its absolute path.
It seems Remove does string matching and not Path matching.
Maybe I have to type into Remove the exact same string as it was Include-ed?
I can remove these files with:
<Content Remove="MyFile2" />
<Content Remove="c:\MyProject\MyFile1" />
I can't remove them with:
<Content Remove="c:\MyProject\MyFile2" />
<Content Remove="MyFile1" />
Is there a way to tell MsBuild these are paths and Remove them always by absolute path?

Answer 1

Items have a set of metadata - see MSBuild well-known item metadata.
%(Identity) will be the string that was used for the item in the Include. But if the Item is a file that exists, then %(FullPath) will have a value.
e.g. Your example items are:
Identity
FullPath
c:\MyProject\MyFile1
c:\MyProject\MyFile1
MyFile2
c:\MyProject\MyFile2
You need to use Identity for the Remove but you can create a new ItemGroup that is a subset of Content by testing the FullPath and then use that ItemGroup as the value of your Remove.
An example might be
<Target Name="Test">
...
<ItemGroup>
<FilesToRemove Include="#(Content)" Condition="'%(FullPath)' == 'c:\MyProject\MyFile1' or '%(FullPath)' == 'c:\MyProject\MyFile2'" />
</ItemGroup>
<ItemGroup>
<Content Remove="#(FilesToRemove)" />
</ItemGroup>
...
</Target>
The FilesToRemove ItemGroup is using task batching and must be within a Target.
Another example of the same approach but testing the file extension:
<Target Name="Test">
...
<ItemGroup>
<FilesToRemove Include="#(Content)" Condition="'%(Extension)' == '.js'" />
</ItemGroup>
<ItemGroup>
<Content Remove="#(FilesToRemove)" MatchOnMetadata="Extension" />
</ItemGroup>
...
</Target>
The Remove attribute accepts wildcards but
<Content Remove="**\*.js" />
won't work because it will not match items added without using a wildcard.