日志记录类（明确FileStream\Dictionary等用法）

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Configuration;

namespace LogHelp
{
    public class LogHelp
    {
        private string _filename;
        private static Dictionary<long, long> lockDic = new Dictionary<long, long>();

        //获取或设置文件名称
        public string FileName
        {
            get { return _filename; }
            set { _filename = value; }
        }

        //构造函数；根据传入的文件名，将日志写到相应的路径下的文件中。
        public LogHelp(string filename)
        {
            string folder = ConfigurationManager.AppSettings["LogPath"]+"\\"+System.DateTime.Now.Date.ToString("yyyyMMdd");
            if (!System.IO.Directory.Exists(folder))
                System.IO.Directory.CreateDirectory(folder);
            if (!filename.ToLower().EndsWith(".txt"))
            {
                filename = filename.Split(‘.‘)[0];
                filename += ".txt";
            }

            _filename = folder + "\\" + filename;
        }

        //创建文件
        public void Create(string fileName)
        {
            if (!System.IO.File.Exists(fileName))
            {
                using (System.IO.FileStream fs= System.IO.File.Create(fileName))
                {
                    fs.Close();
                }
            }
        }

        //写入文本
        private void Write(string content, string newLine)
        {
            if (string.IsNullOrEmpty(_filename))
            {
                throw new Exception("FileName不能为空！");
            }
            using(System.IO.FileStream fs=new System.IO.FileStream(_filename,System.IO.FileMode.OpenOrCreate,System.IO.FileAccess.ReadWrite,System.IO.FileShare.ReadWrite,8,System.IO.FileOptions.Asynchronous))
            {
                //FileStream只能处理字节，须通过编码将字符数据转换成字节。
                //新建字节型数组dataArrary对象，dataArrary对象得到了content+newLine的Encoding的值
                Byte[] dataArrary = System.Text.Encoding .Default.GetBytes(content+newLine);
                bool flag = true;
                long slen = dataArrary.Length;
                long len = 0;
                while (flag)
                {
                    try
                    {
                        if (len >= fs.Length)
                        {
                            fs.Lock(len, slen);
                            lockDic[len] = slen;
                            flag = false;
                        }
                        else
                        {
                            len = fs.Length;
                        }
                    }
                    catch (Exception ex)
                    {
                        while (!lockDic.ContainsKey(len))
                        {
                            len += lockDic[len];
                        }
                    }
                }
                fs.Seek(len, System.IO.SeekOrigin.Begin); //seek设置文件的读取和写入位置
                fs.Write(dataArrary, 0, dataArrary.Length);
                fs.Close();
            }
        }

        //写入文件内容
        public void WriteLine(string content)
        {
            this.Write(content, System.Environment.NewLine);
        }

        //写入文件
        public void Write(string content)
        {
            this.Write(content, "");
        }

    }
}

public class Program
{
     private static LogHelp log = new LogHelp("LogTest");
     static void Main(string[] args)
     {
         log.WriteLine("Hello World");
     }
}

public static void DicSample4()
{
       //1)普通调用
        Dictionary<int, String> dict = new Dictionary<int, String>();
        DictionaryExtensionMethodClass.TryAdd(dict, 1, "ZhangSan");
        DictionaryExtensionMethodClass.TryAdd(dict, 2, "WangWu");
        DictionaryExtensionMethodClass.AddOrPeplace(dict, 3, "WangWu");
        DictionaryExtensionMethodClass.AddOrPeplace(dict, 3, "ZhangWu");
        DictionaryExtensionMethodClass.TryAdd(dict, 2, "LiSi");

        //2)TryAdd 和 AddOrReplace 这两个方法具有较强自我描述能力，用起来很省心，而且也简单：
        dict.AddOrPeplace(20, "Orange");
        dict.TryAdd(21, "Banana");
        dict.TryAdd(22, "apple");

        //3)像Linq或jQuery一样连起来写   
        dict.TryAdd(10, "Bob")
              .TryAdd(11, "Tom")
              .AddOrPeplace(12, "Jom");
        //4) 获取值
        String F = "Ba";
        dict.TryGetValue(31, out F);
        Console.WriteLine("F : {0}",F);

        foreach (var dic in dict)
        {
            Console.WriteLine("Output : Key : {0}, Value : {1}", dic.Key, dic.Value);
        }
        //5)下面是使用GetValue获取值
        var v1 = dict.GetValue(111,null);
        var v2 = dict.GetValue(10,"abc");

        //6)批量添加
        var dict1 = new Dictionary<int,int>();
        dict1.AddOrPeplace(3, 3);
        dict1.AddOrPeplace(5, 5);

        var dict2 = new Dictionary<int, int>();
        dict2.AddOrPeplace(1, 1);
        dict2.AddOrPeplace(4, 4);
        dict2.AddRange(dict1, false);
  }
　　扩展方法所在的类
    public static class DictionaryExtensionMethodClass 
    {
        /// <summary>
        /// 尝试将键和值添加到字典中：如果不存在，才添加；存在，不添加也不抛导常
        /// </summary>
        public static Dictionary<TKey, TValue> TryAdd<TKey, TValue>(this Dictionary<TKey, TValue> dict, TKey key, TValue value)
        {
            if (dict.ContainsKey(key) == false)
                dict.Add(key, value);
            return dict;
        }

        /// <summary>
        /// 将键和值添加或替换到字典中：如果不存在，则添加；存在，则替换
        /// </summary>
        public static Dictionary<TKey, TValue> AddOrPeplace<TKey, TValue>(this Dictionary<TKey, TValue> dict, TKey key, TValue value)
        {
            dict[key] = value;
            return dict;
        }

        /// <summary>
        /// 获取与指定的键相关联的值，如果没有则返回输入的默认值
        /// </summary>
        public static TValue GetValue<TKey, TValue>(this Dictionary<TKey, TValue> dict, TKey key, TValue defaultValue)
        {
            return dict.ContainsKey(key)?dict[key] : defaultValue;
        }

        /// <summary>
        /// 向字典中批量添加键值对
        /// </summary>
        /// <param name="replaceExisted">如果已存在，是否替换</param>
        public static Dictionary<TKey, TValue> AddRange<TKey, TValue>(this Dictionary<TKey, TValue> dict, IEnumerable<KeyValuePair<TKey, TValue>> values, bool replaceExisted)
        {
            foreach (var item in values)
            {
                if (dict.ContainsKey(item.Key) == false || replaceExisted)
                    dict[item.Key] = item.Value;
            }
            return dict;
        }


    }