System.Xml.XmlTextReaderImpl.LookupNamespace C# (CSharp) Method

        private string LookupNamespace(NodeData node)
        {
            string ns = _namespaceManager.LookupNamespace(node.prefix);
            if (ns != null)
            {
                return ns;
            }
            else
            {
                Throw(SR.Xml_UnknownNs, node.prefix, node.LineNo, node.LinePos);
                return null;
            }
        }

        public override string?LookupNamespace(string prefix)
        {
            string?ns = _impl.LookupNamespace(prefix);

            if (ns != null && ns.Length == 0)
            {
                ns = null;
            }
            return(ns);
        }