The newer SDK-style project files (*.csproj) do not support all of the Assembly attributes that could be used in older project files. A simple example is the AssemblyTrademarkAttribute. There is no <Trademark> element defined in the new projects. Arbitrary attributes can however be added like this sample:

<ItemGroup>
    <AssemblyAttribute Include="System.Reflection.AssemblyTrademarkAttribute">
      <_Parameter1>My Trademark</_Parameter1>
    </AssemblyAttribute>
</ItemGroup>

It's a bit ugly and I can't find formal documentation of the elements, but it works fine. Some people are using this technique to add InternalsVisibleTo attributes to their assemblies without the need to manually add an AssemblyInfo.cs file to their project.

An interesting trick is create your own Attribute with a string property and constructor parameter, then use it like this:

<ItemGroup>
    <AssemblyAttribute Include="MyCompany.AssemblyBuildTimeAttribute">
      <_Parameter1>$([System.DateTime]::UtcNow.ToString("yyyy-MM-dd HH:mm:ss"))</_Parameter1>
    </AssemblyAttribute>
</ItemGroup>