System.Xml.Serialization.XmlSerializationWriter.WriteStartElement C# (CSharp) Method

        protected void WriteStartElement(string name, string ns, object o, bool writePrefixed, XmlSerializerNamespaces xmlns)
        {
            if (o != null && _objectsInUse != null)
            {
                if (_objectsInUse.ContainsKey(o)) throw new InvalidOperationException(SR.Format(SR.XmlCircularReference, o.GetType().FullName));
                _objectsInUse.Add(o, o);
            }

            string prefix = null;
            bool needEmptyDefaultNamespace = false;
            if (_namespaces != null)
            {
                foreach (string alias in _namespaces.Namespaces.Keys)
                {
                    string aliasNs = (string)_namespaces.Namespaces[alias];

                    if (alias.Length > 0 && aliasNs == ns)
                        prefix = alias;
                    if (alias.Length == 0)
                    {
                        if (aliasNs == null || aliasNs.Length == 0)
                            needEmptyDefaultNamespace = true;
                        if (ns != aliasNs)
                            writePrefixed = true;
                    }
                }
                _usedPrefixes = ListUsedPrefixes(_namespaces.Namespaces, _aliasBase);
            }
            if (writePrefixed && prefix == null && ns != null && ns.Length > 0)
            {
                prefix = _w.LookupPrefix(ns);
                if (prefix == null || prefix.Length == 0)
                {
                    prefix = NextPrefix();
                }
            }
            if (prefix == null && xmlns != null)
            {
                prefix = xmlns.LookupPrefix(ns);
            }
            if (needEmptyDefaultNamespace && prefix == null && ns != null && ns.Length != 0)
                prefix = NextPrefix();
            _w.WriteStartElement(prefix, name, ns);
            if (_namespaces != null)
            {
                foreach (string alias in _namespaces.Namespaces.Keys)
                {
                    string aliasNs = (string)_namespaces.Namespaces[alias];
                    if (alias.Length == 0 && (aliasNs == null || aliasNs.Length == 0))
                        continue;
                    if (aliasNs == null || aliasNs.Length == 0)
                    {
                        if (alias.Length > 0)
                            throw new InvalidOperationException(SR.Format(SR.XmlInvalidXmlns, alias));
                        WriteAttribute(nameof(xmlns), alias, null, aliasNs);
                    }
                    else
                    {
                        if (_w.LookupPrefix(aliasNs) == null)
                        {
                            // write the default namespace declaration only if we have not written it already, over wise we just ignore one provided by the user
                            if (prefix == null && alias.Length == 0)
                                break;
                            WriteAttribute(nameof(xmlns), alias, null, aliasNs);
                        }
                    }
                }
            }
            WriteNamespaceDeclarations(xmlns);
        }