Dump ItemGroup content with meta data.

GetMetadataTask.xml

<!-- From  https://stackoverflow.com/questions/17461175/how-to-get-all-the-metadata-keys-for-any-itemgroup-item -->
<UsingTask TaskName="GetMetadataTask"
            TaskFactory="RoslynCodeTaskFactory"
            AssemblyFile="$(MSBuildToolsPath)\Microsoft.Build.Tasks.Core.dll" >
    <ParameterGroup>
        <MyItemGroup ParameterType="Microsoft.Build.Framework.ITaskItem[]" Required="true" />
        <MetadataString Output="true" />
    </ParameterGroup>
    <Task>
        <Using Namespace="System"/>
        <Code Type="Fragment" Language="cs">
            <![CDATA[
        StringBuilder command = new StringBuilder();
        foreach (ITaskItem item in MyItemGroup )
        {
            command.AppendFormat("ItemName={0}\r\n", item);
            foreach (string parameter in item.MetadataNames)
            {
                command.AppendFormat("  {0}={1}\r\n", parameter, item.GetMetadata(parameter));
            }
            command.AppendFormat("\r\n");
        }
        MetadataString = command.ToString();
    ]]>
        </Code>
    </Task>
</UsingTask>
<!-- Usage (here for Reference). -->
<Target Name="PrintReferencesItemGroup" AfterTargets="ResolveReferences">
    <GetMetadataTask MyItemGroup="@(Reference)">
        <Output TaskParameter="MetadataString" PropertyName="YourMetadataString"/>
    </GetMetadataTask>
    <Message Text="$(YourMetadataString)" Importance="High" />
</Target>