1 public static IDictionary<TKey, TResult> MapReduce<TInput, TKey, TValue, TResult>(this IEnumerable<TInput> inputList, 2             Func<TInput, KeyValueClass<TKey, TValue>> map, Func<TKey, IEnumerable<TValue>, TResult> reduce) 3         { 4             object locker = new object(); 5             ConcurrentDictionary<TKey, TResult> result = new ConcurrentDictionary<TKey, TResult>(); 6             //保存map出来的结果 7             ConcurrentDictionary<TKey, ConcurrentBag<TValue>> mapDic = new ConcurrentDictionary<TKey, ConcurrentBag<TValue>>(); 8             //并行map 9             Parallel.ForEach(inputList, (t, p, s) =>10             {11                 var pair = map(t);12                 if (pair != null)13                 {14                     //锁住防止并发操作list造成数据缺失15                     lock (locker)16                     {17                         //将匹配出来的结果加入结果集放入字典18                         ConcurrentBag<TValue> list = null;19                         if (mapDic.ContainsKey(pair.Key))20                         {21                             list = mapDic[pair.Key];22                         }23                         else24                         {25                             list = new ConcurrentBag<TValue>();26                             mapDic[pair.Key] = list;27                         }28                         list.Add(pair.Value);29                     }30                 }31             });32 33             //并行reduce34             Parallel.ForEach(mapDic.Keys, (t, p, s) =>35             {36                 result[t] = reduce(t, mapDic[t]);37             });38             return result;39         }

 1 public class KeyValueClass<K, V> 2     { 3         public KeyValueClass(K key, V value) 4         { 5             Key = key; 6             Value =http://www.mamicode.com/ value; 7         } 8  9         public KeyValueClass()10         {11 12         }13 14         public K Key { get; set; }15 16         public V Value { get; set; }17     }

 1 List<TestClass> listTestClass = new List<TestClass>(); 2             listTestClass.Add(new TestClass { a = "a", g = 1 }); 3             listTestClass.Add(new TestClass { a = "b", g = 3 }); 4             listTestClass.Add(new TestClass { a = "c", g = 4 }); 5             listTestClass.Add(new TestClass { a = "d", g = 2 }); 6             listTestClass.Add(new TestClass { a = "e", g = 1 }); 7             listTestClass.Add(new TestClass { a = "f", g = 2 }); 8             listTestClass.Add(new TestClass { a = "g", g = 5 }); 9             listTestClass.Add(new TestClass { a = "h", g = 6 });10             IDictionary<int, string> dic = listTestClass.MapReduce(t =>11             {12                 if (t.g < 5)13                 {14                     return new KeyValueClass<int, string>(t.g, t.a);15                 }16                 return null;17             }, (key, values) =>18            {19                return string.Join(",", values);20            });

 1 public class TestClass 2     { 3         public string a { get; set; } 4         public string b { get; set; } 5  6         public string d { get; set; } 7  8         //public DateTime f { get; set; } 9 10         public int g { get; set; }11 12         public List<TestClass> test { get; set; }13 14         public Dictionary<string, string> dic { get; set; }15     }