C# 实现敏感词过滤

　　实现 该 敏感词过滤 采用的是 dfa算法，参考文章：

　　具体 实现 步骤 如下：

　　第一步，构建 敏感词库（wordslibrary）  类：

using system.collections.generic;
using system.linq;
using system;

namespace contentsafe.sensitiveword
{
    /// <summary>
    /// 敏感词库
    /// </summary>
    public class wordslibrary
    {
        /// <summary>
        /// 词库树结构类
        /// </summary>
        public class itemtree
        {
            public char item { get; set; }
            public bool isend { get; set; }
            public list<itemtree> child { get; set; }
        }

        /// <summary>
        /// 词库树
        /// </summary>
        public itemtree library { get; private set; }

        /// <summary>
        /// 敏感词组
        /// </summary>
        public string[] words { get; protected set; }

        /// <summary>
        /// 敏感词库
        /// </summary>
        public wordslibrary()
        {
            loadwords();
            init();
        }

        /// <summary>
        /// 敏感词库
        /// </summary>
        /// <param name="words">敏感词组</param>
        public wordslibrary(string[] words) : this()
        {
            words = words;
        }

        /// <summary>
        /// 加载 敏感词组，可被重写以自定义 如何加载 敏感词组
        /// </summary>
        public virtual void loadwords()
        {
        }

        /// <summary>
        /// 词库初始化
        /// </summary>
        private void init()
        {
            if (words == null)
                words = new[] { "" };

            library = new itemtree() { item = 'r', isend = false, child = createtree(words) };
        }

        /// <summary>
        /// 创建词库树
        /// </summary>
        /// <param name="words">敏感词组</param>
        /// <returns></returns>
        private list<itemtree> createtree(string[] words)
        {
            list<itemtree> tree = null;

            if (words != null && words.length > 0)
            {
                tree = new list<itemtree>();

                foreach (var item in words)
                    if (!string.isnullorempty(item))
                    {
                        char cha = item[0];

                        itemtree node = tree.find(e => e.item == cha);
                        if (node != null)
                            addchildtree(node, item);
                        else
                            tree.add(createsingletree(item));
                    }
            }

            return tree;
        }

        /// <summary>
        /// 创建单个完整树
        /// </summary>
        /// <param name="word">单个敏感词</param>
        /// <returns></returns>
        private itemtree createsingletree(string word)
        {
            //根节点，此节点 值为空
            itemtree root = new itemtree();
            //移动 游标
            itemtree p = root;

            for (int i = 0; i < word.length; i++)
            {
                itemtree child = new itemtree() { item = word[i], isend = false, child = null };
                p.child = new list<itemtree>() { child };
                p = child;
            }
            p.isend = true;

            return root.child.first();
        }

        /// <summary>
        /// 附加分支子树
        /// </summary>
        /// <param name="childtree">子树</param>
        /// <param name="word">单个敏感词</param>
        private void addchildtree(itemtree childtree, string word)
        {
            //移动 游标
            itemtree p = childtree;

            for (int i = 1; i < word.length; i++)
            {
                char cha = word[i];
                list<itemtree> child = p.child;

                if (child == null)
                {
                    itemtree node = new itemtree() { item = cha, isend = false, child = null };
                    p.child = new list<itemtree>() { node };
                    p = node;
                }
                else
                {
                    itemtree node = child.find(e => e.item == cha);
                    if (node == null)
                    {
                        node = new itemtree() { item = cha, isend = false, child = null };
                        child.add(node);
                        p = node;
                    }
                    else
                        p = node;
                }
            }
            p.isend = true;
        }
    }
}

　　第二步，构建 敏感词检测（contentcheck） 类：

using system.collections.generic;
using system.linq;
using system;

namespace contentsafe.sensitiveword
{
    /// <summary>
    /// 敏感词检测
    /// </summary>
    public class contentcheck
    {
        /// <summary>
        /// 检测文本
        /// </summary>
        public string text { private get; set; }

        /// <summary>
        /// 敏感词库 词树
        /// </summary>
        public wordslibrary.itemtree library { private get; set; }

        /// <summary>
        /// 敏感词检测
        /// </summary>
        public contentcheck() { }

        /// <summary>
        /// 敏感词检测
        /// </summary>
        /// <param name="library">敏感词库</param>
        public contentcheck(wordslibrary library)
        {
            if (library.library == null)
                throw new exception("敏感词库未初始化");

            library = library.library;
        }

        /// <summary>
        /// 敏感词检测
        /// </summary>
        /// <param name="library">敏感词库</param>
        /// <param name="text">检测文本</param>
        public contentcheck(wordslibrary library, string text) : this(library)
        {
            if (text == null)
                throw new exception("检测文本不能为null");

            text = text;
        }

        /// <summary>
        /// 检测敏感词
        /// </summary>
        /// <param name="text">检测文本</param>
        /// <returns></returns>
        private dictionary<int, char> wordscheck(string text)
        {
            if (library == null)
                throw new exception("未设置敏感词库 词树");

            dictionary<int, char> dic = new dictionary<int, char>();
            wordslibrary.itemtree p = library;
            list<int> indexs = new list<int>();

            for (int i = 0, j = 0; j < text.length; j++)
            {
                char cha = text[j];
                var child = p.child;

                var node = child.find(e => e.item == cha);
                if (node != null)
                {
                    indexs.add(j);
                    if (node.isend || node.child == null)
                    {
                        if (node.child != null)
                        {
                            int k = j + 1;
                            if (k < text.length && node.child.exists(e => e.item == text[k]))
                            {
                                p = node;
                                continue;
                            }
                        }

                        foreach (var item in indexs)
                            dic.add(item, text[item]);

                        indexs.clear();
                        p = library;
                        i = j;
                        ++i;
                    }
                    else
                        p = node;
                }
                else
                {
                    indexs.clear();
                    if (p.gethashcode() != library.gethashcode())
                    {
                        ++i;
                        j = i;
                        p = library;
                    }
                    else
                        i = j;
                }
            }

            return dic;
        }

        /// <summary>
        /// 替换敏感词
        /// </summary>
        /// <param name="library">敏感词库</param>
        /// <param name="text">检测文本</param>
        /// <param name="newchar">替换字符</param>
        /// <returns></returns>
        public static string sensitivewordsreplace(wordslibrary library, string text, char newchar = '*')
        {
            dictionary<int, char> dic = new contentcheck(library).wordscheck(text);
            if (dic != null && dic.keys.count > 0)
            {
                char[] chars = text.tochararray();
                foreach (var item in dic)
                    chars[item.key] = newchar;

                text = new string(chars);
            }

            return text;
        }

        /// <summary>
        /// 替换敏感词
        /// </summary>
        /// <param name="text">检测文本</param>
        /// <param name="newchar">替换字符</param>
        /// <returns></returns>
        public string sensitivewordsreplace(string text, char newchar = '*')
        {
            dictionary<int, char> dic = wordscheck(text);
            if (dic != null && dic.keys.count > 0)
            {
                char[] chars = text.tochararray();
                foreach (var item in dic)
                    chars[item.key] = newchar;

                text = new string(chars);
            }

            return text;
        }

        /// <summary>
        /// 替换敏感词
        /// </summary>
        /// <param name="newchar">替换字符</param>
        /// <returns></returns>
        public string sensitivewordsreplace(char newchar = '*')
        {
            if (text == null)
                throw new exception("未设置检测文本");

            return sensitivewordsreplace(text, newchar);
        }

        /// <summary>
        /// 查找敏感词
        /// </summary>
        /// <param name="library">敏感词库</param>
        /// <param name="text">检测文本</param>
        /// <returns></returns>
        public static list<string> findsensitivewords(wordslibrary library, string text)
        {
            contentcheck check = new contentcheck(library, text);
            return check.findsensitivewords();
        }

        /// <summary>
        /// 查找敏感词
        /// </summary>
        /// <param name="text">检测文本</param>
        /// <returns></returns>
        public list<string> findsensitivewords(string text)
        {
            dictionary<int, char> dic = wordscheck(text);
            if (dic != null && dic.keys.count > 0)
            {
                int i = -1;
                string str = "";
                list<string> list = new list<string>();
                foreach(var item in dic)
                {
                    if (i == -1 || i + 1 == item.key)
                        str += item.value;
                    else
                    {
                        list.add(str);
                        str = "" + item.value;
                    }

                    i = item.key;
                }
                list.add(str);

                return list.distinct().tolist();
            }
            else
                return null;
        }

        /// <summary>
        /// 查找敏感词
        /// </summary>
        /// <returns></returns>
        public list<string> findsensitivewords()
        {
            if (text == null)
                throw new exception("未设置检测文本");

            return findsensitivewords(text);
        }
    }
}

　　第三步，测试与使用方法：

string[] words = new[] { "敏感词1", "敏感词2", "含有", "垃圾" }; //敏感词组 可自行在网上 搜索下载

//敏感词库 类可被继承，如果想实现自定义 敏感词导入方法 可以 对 loadwords 方法进行 重写
var library = new wordslibrary(words); //实例化 敏感词库

string text = "在任意一个文本中都可能包含敏感词1、2、3等等，只要含有敏感词都会被找出来，比如：垃圾";
contentcheck check = new contentcheck(library, text);  //实例化 内容检测类
var list = check.findsensitivewords();    //调用 查找敏感词方法 返回敏感词列表
var str = check.sensitivewordsreplace();  //调用 敏感词替换方法 返回处理过的字符串

　　该 实现方案 不止 这个 使用方法，更多使用方法 可自行 研究