C#扩展一般用于linq

下面是dictionary的扩展

 using System.Collections.Generic;

 namespace NetAnalysis.Common
 {

   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;

         }

   }
 }