System.Xml.Xsl.Xslt.XsltLoader.ParseModeListAttribute C# (CSharp) Method

        private QilName ParseModeListAttribute(int attNum)
        {
            //Debug.Assert(input.IsXsltKeyword(atoms.Template) && !V1);
            if (!_input.MoveToXsltAttribute(attNum, "mode"))
            {
                return nullMode;
            }

            string modeList = _input.Value;
            if (modeList == "#all")
            {
                ReportNYI("xsl:template[@mode='#all']");
                return nullMode;
            }
            else
            {
                string[] list = XmlConvert.SplitString(modeList);
                List<QilName> modes = new List<QilName>(list.Length);

                _compiler.EnterForwardsCompatible();  // mode is always optional attribute

                if (list.Length == 0)
                {
                    ReportError(SR.Xslt_ModeListEmpty);
                }
                else
                {
                    foreach (string qname in list)
                    {
                        QilName mode;
                        if (qname == "#default")
                        {
                            mode = nullMode;
                        }
                        else if (qname == "#current")
                        {
                            ReportNYI("xsl:apply-templates[@mode='#current']");
                            break;
                        }
                        else if (qname == "#all")
                        {
                            ReportError(SR.Xslt_ModeListAll);
                            break;
                        }
                        else
                        {
                            mode = CreateXPathQName(qname);
                        }
                        bool dup = false;
                        foreach (QilName m in modes)
                        {
                            dup |= m.Equals(mode);
                        }
                        if (dup)
                        {
                            ReportError(SR.Xslt_ModeListDup, qname);
                        }
                        else
                        {
                            modes.Add(mode);
                        }
                    }
                }

                if (!_compiler.ExitForwardsCompatible(_input.ForwardCompatibility))
                {
                    modes.Clear();
                    modes.Add(nullMode);
                }
                if (1 < modes.Count)
                {
                    ReportNYI("Multipe modes");
                    return nullMode;
                }
                if (modes.Count == 0)
                {
                    return nullMode;
                }
                return modes[0];
            }
        }