C# Stack.FirstOrDefault方法代码示例

        public static ParsedData Parse(string data)
        {
            if (data != null && data.Length > 0)
            {
                var curr = Start (data[0]);
                var stk = new Stack<Token> ();

                stk.Push (curr);

                for (var i = 1; i < data.Length; i++)
                {
                    curr = curr.Parse (data[i]);

                    if (stk.Peek () != curr)
                        stk.Push (curr);
                }

                if (stk.Any (x => x is Error))
                    return new ParsedData ();
                else
                {
                    var title = stk.FirstOrDefault (x => x is Title);
                    var id = stk.FirstOrDefault (x => x is ID);
                    var path = stk.FirstOrDefault (x => x is Path);

                    return new ParsedData (title != null ? title.ToString () : null, path != null ? path.ToString () : null, id != null ? id.ToString () : null);
                }

            }
            else
                return new ParsedData ();
        }

        private string ParagraphHandler(string paragraph, DiaryMode mode)
        {
            var pbuilder = new StringBuilder();

            var paragraphPlugins = new Stack<IDiaryParagraphPlugin>(Plugins.OfType<IDiaryParagraphPlugin>());
            var linePlugins = new Stack<IDiaryLinePlugin>(Plugins.OfType<IDiaryLinePlugin>());
            var linkPlugins = new Stack<IDiaryLinkPlugin>(Plugins.OfType<IDiaryLinkPlugin>());

            Action<IList<string>> prevYield = lines => {
                // do line plugins
                while (linePlugins.Count > 0) {
                    var plugin = linePlugins.Pop();
                    lines = lines.SelectMany(x => plugin.Handle(x, mode)).ToArray();
                }

                var linkRegex = new Regex(@"\[([^\]]+)\]");
                var result = lines.Select(l => linkRegex.Replace(l, me => {
                    var content = me.Groups[1].Value;
                    var plugin = linkPlugins.FirstOrDefault(lp => lp.CanHandle(content, mode));
                    return plugin == null ? content : me.Result(plugin.Handle(content, mode));
                }));

                // join final result into one string
                pbuilder.Append(string.Join("\r\n", result));
            };
            while (paragraphPlugins.Count > 0) {
                var plugin = paragraphPlugins.Pop();
                var wrappedYield = prevYield;
                prevYield = l => plugin.Handle(l, mode, pbuilder, wrappedYield);
            }

            prevYield(paragraph.Split(new[] { "\r\n" }, StringSplitOptions.None));
            return pbuilder.ToString();
        }

//.........这里部分代码省略.........
                        break;
                    case PartType.Parenthesis:
                        if (CurrentPart.Value[0] == '(')
                            if (!needValue)
                                throw new Exception("Неуместная открывающая скобка: позиция " + CurrentPart.Position.ToString());
                            else
                                depth++;
                        else
                            if (depth == 0 || needValue)
                                throw new Exception("Неуместная закрывающая скобка: позиция " + CurrentPart.Position.ToString());
                            else
                                depth--;
                        break;
                    case PartType.Sign:
                        Operation CurrentOperation;
                        if (needValue)
                            if (CurrentPart.Value[0] == '-')
                            {
                                CurrentOperation.Sign = '~';
                                CurrentOperation.Precedence = depth * 10 + 1;
                                OpStack.Push(CurrentOperation);
                            }
                            else
                                throw new Exception("Неуместный знак: (" + CurrentPart.Value.ToString() + "): позиция "
                                                                               + CurrentPart.Position.ToString());
                        else
                        {
                            CurrentOperation.Sign = CurrentPart.Value[0];
                            CurrentOperation.Precedence = 0;
                            switch (CurrentPart.Value[0])
                            {
                                case '+':
                                    CurrentOperation.Precedence = depth * 10 + 1;
                                    break;
                                case '-':
                                    CurrentOperation.Precedence = depth * 10 + 1;
                                    break;
                                case '*':
                                    CurrentOperation.Precedence = depth * 10 + 2;
                                    break;
                                case '/':
                                    CurrentOperation.Precedence = depth * 10 + 2;
                                    break;
                                case '^':
                                    CurrentOperation.Precedence = depth * 10 + 3;
                                    break;
                            }
                            Reduce(CurrentOperation.Precedence);
                            OpStack.Push(CurrentOperation);
                            needValue = true;
                        }

                        break;
                    case PartType.Identifier:
                        if (!needValue)
                            throw new Exception("Неуместный идиентификатор: (" + CurrentPart.Value.ToString() +
                                "): позиция " + CurrentPart.Position.ToString());
                        foreach (Identifier CurrentIdentifier in Identifiers)
                        {
                            if ((CurrentPart.Value).ToLower() == (CurrentIdentifier.IdentifierString).ToLower())
                            {
                                ArgStack.Push(CurrentIdentifier.Value);
                                IsNew = false;
                            }
                            else
                                IsNew = true;
                            if (IsNew == false)
                                break;
                        }

                        if (IsNew == true)
                        {
                            Console.WriteLine("Введите значение идиентификатора {0:s}:", CurrentPart.Value);
                            ID.IdentifierString = CurrentPart.Value;
                            bool Check = double.TryParse(Console.ReadLine(), out ID.Value);
                            if (Check == false)
                                throw new Exception("Неверное значение идиентификатора (" + CurrentPart.Value + ')');
                            ArgStack.Push(ID.Value);
                            Identifiers.Add(ID);
                        }
                        needValue = false;
                        break;
                }
                // Вывод списка лексем с текущими состояниями стеков аргументов и операций
                Console.WriteLine("__________________");
                Console.WriteLine("Обработка лексемы № {0:d}", n);
                Console.WriteLine("Стек аргументов: ");
                foreach (double Arg in ArgStack)
                    Console.WriteLine("{0:g}", Arg.ToString());
                Console.WriteLine("Стек операций:");
                foreach (Operation Op in OpStack)
                    Console.WriteLine("{0:g} ({1:d})", Op.Sign.ToString(), Op.Precedence.ToString());
            }
            Reduce(0);
            if (depth > 0)
            {
                throw new Exception("Не закрыты скобки в конце строки");
            }
            return ArgStack.FirstOrDefault();
        }

        public static IList<ParsedChunk> ParseChunk(string input)
        {
            #region init

            // init
            var toReturn = new List<ParsedChunk>();
            var openTags = new Stack<BbTag>();
            var tags = new Queue<BbTag>();
            var processedQueue = new Queue<BbTag>();

            var finder = new BbFinder(input);

            // find all tags
            while (!finder.HasReachedEnd)
            {
                var next = finder.Next();
                if (next != null)
                    tags.Enqueue(next);
            }


            // return original input if we've no valid bbcode tags
            if (tags.All(x => x.Type == BbCodeType.None))
                return new[] {AsChunk(input)};

            #endregion

            while (tags.Count > 0)
            {
                // get the next tag to process
                var tag = tags.Dequeue();
                var addToQueue = true;

                #region add as child of last tag

                // check if we're in the context of another open tag
                if (openTags.Count > 0)
                {
                    var lastOpen = openTags.Peek();
                    var lastMatching = openTags.FirstOrDefault(x => tag.IsClosing && x.Type == tag.Type);

                    // check if we're closing any previous tags
                    if (lastMatching != null)
                    {
                        lastMatching.ClosingTag = tag;

                        // keep going through our opened tag stack until we find the one
                        // we're closing
                        do
                        {
                            lastOpen = openTags.Pop();

                            // if we end up with a tag that isn't the one we're closing,
                            // it must not have been closed correctly, e.g
                            // [i] [b] [/i]
                            // we'll treat that '[b]' as text
                            if (lastOpen != lastMatching) lastOpen.Type = BbCodeType.None;
                        } while (lastOpen != lastMatching);

                        #region handle noparse

                        if (lastMatching.Type == BbCodeType.NoParse)
                        {
                            lastMatching.Children = lastMatching.Children ?? new List<BbTag>();
                            lastMatching.Children.Add(new BbTag
                            {
                                Type = BbCodeType.None,
                                End = tag.Start,
                                Start = lastMatching.End
                            });
                        }

                        #endregion
                    }
                    else
                    {
                        if (openTags.All(x => x.Type != BbCodeType.NoParse))
                        {
                            // if not, we have to be a child of it
                            lastOpen.Children = lastOpen.Children ?? new List<BbTag>();

                            lastOpen.Children.Add(tag);
                        }

                        // any matching closing tags would be caught in the if part of this
                        // branch, this is an invalid tag, treat as text
                        if (tag.IsClosing) tag.Type = BbCodeType.None;

                        addToQueue = false;
                    }
                }

                #endregion

                // we don't need to continue processing closing tags
                if (tag.IsClosing) continue;

                // tell the system we're in the context of this tag now
                // though ignore children of 'text' and 'hr'
                if (tag.Type != BbCodeType.None && tag.Type != BbCodeType.HorizontalRule)
//.........这里部分代码省略.........