public virtual void AddNamespace(string prefix, string uri)
        {
            if (uri == null)
            {
                throw new ArgumentNullException("uri");
            }

            if (prefix == null)
            {
                throw new ArgumentNullException("prefix");
            }

            prefix = _nameTable.Add(prefix);
            uri    = _nameTable.Add(uri);

            if ((Ref.Equal(_xml, prefix) && !uri.Equals(XmlReservedNs.NsXml)))
            {
                throw new ArgumentException(ResXml.Xml_XmlPrefix);
            }
            if (Ref.Equal(_xmlNs, prefix))
            {
                throw new ArgumentException(ResXml.Xml_XmlnsPrefix);
            }

            int declIndex         = LookupNamespaceDecl(prefix);
            int previousDeclIndex = -1;

            if (declIndex != -1)
            {
                if (_nsdecls[declIndex].scopeId == _scopeId)
                {
                    // redefine if in the same scope
                    _nsdecls[declIndex].uri = uri;
                    return;
                }
                else
                {
                    // othewise link
                    previousDeclIndex = declIndex;
                }
            }

            // set new namespace declaration
            if (_lastDecl == _nsdecls.Length - 1)
            {
                NamespaceDeclaration[] newNsdecls = new NamespaceDeclaration[_nsdecls.Length * 2];
                Array.Copy(_nsdecls, 0, newNsdecls, 0, _nsdecls.Length);
                _nsdecls = newNsdecls;
            }

            _nsdecls[++_lastDecl].Set(prefix, uri, _scopeId, previousDeclIndex);

            // add to hashTable
            if (_useHashtable)
            {
                _hashTable[prefix] = _lastDecl;
            }
            // or create a new hashTable if the threashold has been reached
            else if (_lastDecl >= MinDeclsCountForHashtable)
            {
                // add all to hash table
                Debug.Assert(_hashTable == null);
                _hashTable = new Dictionary <string, int>(_lastDecl);
                for (int i = 0; i <= _lastDecl; i++)
                {
                    _hashTable[_nsdecls[i].prefix] = i;
                }
                _useHashtable = true;
            }
        }
        // SxS: This function calls ValidateElement on XmlSchemaValidator which is annotated with ResourceExposure attribute.
        // Since the resource names (namespace location) are not provided directly by the user (they are read from the source
        // document) and the function does not expose any resources it is fine to disable the SxS warning.


        private async Task ProcessElementEventAsync()
        {
            if (_processInlineSchema && IsXSDRoot(_coreReader.LocalName, _coreReader.NamespaceURI) && _coreReader.Depth > 0)
            {
                _xmlSchemaInfo.Clear();
                _attributeCount = _coreReaderAttributeCount = _coreReader.AttributeCount;
                if (!_coreReader.IsEmptyElement)
                { //If its not empty schema, then parse else ignore
                    _inlineSchemaParser = new Parser(SchemaType.XSD, _coreReaderNameTable, _validator.SchemaSet.GetSchemaNames(_coreReaderNameTable), _validationEvent);
                    await _inlineSchemaParser.StartParsingAsync(_coreReader, null).ConfigureAwait(false);

                    _inlineSchemaParser.ParseReaderNode();
                    _validationState = ValidatingReaderState.ParseInlineSchema;
                }
                else
                {
                    _validationState = ValidatingReaderState.ClearAttributes;
                }
            }
            else
            { //Validate element
                //Clear previous data
                _atomicValue = null;
                _originalAtomicValueString = null;
                _xmlSchemaInfo.Clear();

                if (_manageNamespaces)
                {
                    _nsManager.PushScope();
                }
                //Find Xsi attributes that need to be processed before validating the element
                string xsiSchemaLocation = null;
                string xsiNoNamespaceSL  = null;
                string xsiNil            = null;
                string xsiType           = null;
                if (_coreReader.MoveToFirstAttribute())
                {
                    do
                    {
                        string objectNs   = _coreReader.NamespaceURI;
                        string objectName = _coreReader.LocalName;
                        if (Ref.Equal(objectNs, _nsXsi))
                        {
                            if (Ref.Equal(objectName, _xsiSchemaLocation))
                            {
                                xsiSchemaLocation = _coreReader.Value;
                            }
                            else if (Ref.Equal(objectName, _xsiNoNamespaceSchemaLocation))
                            {
                                xsiNoNamespaceSL = _coreReader.Value;
                            }
                            else if (Ref.Equal(objectName, _xsiType))
                            {
                                xsiType = _coreReader.Value;
                            }
                            else if (Ref.Equal(objectName, _xsiNil))
                            {
                                xsiNil = _coreReader.Value;
                            }
                        }
                        if (_manageNamespaces && Ref.Equal(_coreReader.NamespaceURI, _nsXmlNs))
                        {
                            _nsManager.AddNamespace(_coreReader.Prefix.Length == 0 ? string.Empty : _coreReader.LocalName, _coreReader.Value);
                        }
                    } while (_coreReader.MoveToNextAttribute());
                    _coreReader.MoveToElement();
                }
                _validator.ValidateElement(_coreReader.LocalName, _coreReader.NamespaceURI, _xmlSchemaInfo, xsiType, xsiNil, xsiSchemaLocation, xsiNoNamespaceSL);
                ValidateAttributes();
                _validator.ValidateEndOfAttributes(_xmlSchemaInfo);
                if (_coreReader.IsEmptyElement)
                {
                    await ProcessEndElementEventAsync().ConfigureAwait(false);
                }
                _validationState = ValidatingReaderState.ClearAttributes;
            }
        }