System.Xml.Xsl.Runtime.XsltFunctions.MSNamespaceUri C# (CSharp) Method

        public static string MSNamespaceUri(string name, XPathNavigator currentNode)
        {
            int colonOffset;
            int len = ValidateNames.ParseQName(name, 0, out colonOffset);

            if (len != name.Length)
            {
                return string.Empty;
            }
            string prefix = name.Substring(0, colonOffset);
            if (prefix == "xmlns")
            {
                return string.Empty;
            }
            string ns = currentNode.LookupNamespace(prefix);
            if (ns != null)
            {
                return ns;
            }
            if (prefix == "xml")
            {
                return XmlReservedNs.NsXml;
            }
            return string.Empty;
        }