How do I get the current subdomain within .Net Core middleware?

I have managed to work out my own answer in the meantime...comments appreciated.

private static string GetSubDomain(HttpContext httpContext)
        {
            var subDomain = string.Empty;

            var host = httpContext.Request.Host.Host;

            if (!string.IsNullOrWhiteSpace(host))
            {
                subDomain = host.Split('.')[0];
            }

            return subDomain.Trim().ToLower();
        }