Can I deny access to an Assembly attribute from outside the assembly it is applied to?

Can I mark an assembly attribute (like [assembly: AssemblyMetadata("key", "value")]) as private/internal to make it only accessible from within the assembly it is applied to?

Background: I have just tested a technique to get some build information in code (e.g. the solution directory) via the AssemblyMetadata attribute and a custom msbuild target by adding the following class to the project and msbuild target to the *.csproj file:

static class BuildEnvironment
{
    static string _solutionDir;

    public static string SolutionDirectory
    {
        get
        {
            if (_solutionDir == null)
                _solutionDir = Initialize();
            return _solutionDir;

            string Initialize()
            {
                var metadata = typeof(BuildEnvironment).GetTypeInfo().Assembly.GetCustomAttributes<AssemblyMetadataAttribute>();
                return metadata.FirstOrDefault((x) => x.Key == "SolutionDir")?.Value ?? string.Empty;
            }
        }
    }
}


<Target Name="GenerateBuildEnvironment" BeforeTargets="CoreCompile">
    <ItemGroup>
        <AssemblyAttributes Include="AssemblyMetadata">
            <_Parameter1>SolutionDir</_Parameter1>
            <_Parameter2>$(SolutionDir)</_Parameter2>
        </AssemblyAttributes>
    </ItemGroup>
    <WriteCodeFragment AssemblyAttributes="@(AssemblyAttributes)" Language="C#" OutputDirectory="$(IntermediateOutputPath)">
        <Output TaskParameter="OutputFile" ItemName="Compile" />
    </WriteCodeFragment>
</Target>