IdentityUtil

IdentityUtil.cs

    public static class IdentityUtil
    {
        public static string GetCurrentIdentityDomainName()
        {
            var identity = WindowsIdentity.GetCurrent();
            if (identity == null || !identity.IsAuthenticated || identity.IsSystem)
                return null;

            return GetDomainName(identity.Name);
        }

        public static string GetDomainName(string fullUserName)
        {
            if (fullUserName == null)
                return null;

            var index = fullUserName.IndexOf("\\", StringComparison.Ordinal);
            if (index == -1)
                return null;

            var domain = fullUserName.Substring(0, index);
              return domain;
        }
    }

System.Environment.UserDomainName