如何连接两个字典收藏LINQ查询

Question

我的第一个数据收集是这样的：

IEnumerable<Dictionary<string, object>> firstSourceData; 

的项目是这样的：

new Dictionary<string, object> 
{ 
    ["id"] = 1, 
    ["name"] = "some", 
    ["age"] = 30 
} 

我的第二个数据是另一个字典集合：

IEnumerable<Dictionary<string, object>> secondSourceData; 

项目如下：

new Dictionary<string, object> 
{ 
    ["id"] = 1, 
    ["sales"] = 58, 
    ["age"] = 30 
} 

这两个数据来自不同的来源，我将创建一个不包含重复值的单个字典集合。只有Id键才是Dictianaries的标准，其他属性可能会发生变化。

IEnumerable<Dictionary<string, object>> joined; 

new Dictionary<string, object> 
{ 
    ["id"] = 1, 
    ["sales"] = 58, 
    ["name"] = "some", 
    ["age"] = 30 
}, 

我该怎么用LINQ lambda表达式来做这件事？ （而且是没有任何问题，如果源长度差）

Answer 1

这是你在找什么做：

• 合并词典的两个集合。
• 按“id”键值分组项目。
• 对于每个组你有多个字典，所以使用SelectMany来平整，然后GroupBy上的关键。现在您可以重新创建字典 - ToDictionary。注意你可能有自己重复的键，这就是为什么嵌套GroupBy和值选择你想要的。在这里，我只是用FirstOrDefault

所以：

var result = firstSourceData.Concat(secondSourceData) 
       .GroupBy(item => item["id"]) 
       .Select(group => group.SelectMany(item => item) 
             .GroupBy(item => item.Key) 
             .ToDictionary(key => key.Key, 
                value => value.FirstOrDefault().Value)); 

---

这是结果：

new Dictionary<string, object> 
{ 
    ["id"] = 1, 
    ["sales"] = 58, 
    ["name"] = "some", 
    ["age"] = 30 
}, 
new Dictionary<string, object> 
{ 
    ["id"] = 2, 
    ["sales"] = 58, 
    ["age"] = 30 
} 

对于这个测试案例：

var firstSourceData = new List<Dictionary<string, object>> 
{ 
    new Dictionary<string, object> 
    { 
     ["id"] = 1, 
     ["sales"] = 58, 
     ["age"] = 30 
    }, 
    new Dictionary<string, object> 
    { 
     ["id"] = 2, 
     ["sales"] = 58, 
     ["age"] = 30 
    } 
}; 

var secondSourceData = new List<Dictionary<string, object>> 
{ 
    new Dictionary<string, object> 
    { 
     ["id"] = 1, 
     ["name"] = "some", 
     ["age"] = 30 
    } 
}; 

Answer 2

你可以做联盟：

Dictionary<string,object> dict1 = new Dictionary<string, object>(); 
     dict1.Add("id", 1); 
     dict1.Add("name", "Some"); 
     dict1.Add("age", 30); 

     Dictionary<string, object> dict2 = new Dictionary<string, object>(); 
     dict2.Add("id", 1); 
     dict2.Add("sales", 58); 
     dict2.Add("age", 30); 

     Dictionary<string, object> dict3 = new Dictionary<string, object>(); 
     dict3 = dict1.Union(dict2).ToDictionary(c => c.Key, c => c.Value); 

结果值：

[0] = {[id, 1]} 
[1] = {[name, Some]} 
[2] = {[age, 30]} 
[3] = {[sales, 58]} 

Answer 3

与concat

IEnumerable<Dictionary<string, object>> joined; 

joined= firstSSourceData.Concat(secondSourceData.Where(a => !firstSSourceData.ContainsKey(a.Key))); 

Answer 4

做到这一点你可以这样使用Join

from dict1 in firstSourceData 
join dict2 in secondSourceData 
on dict1["id"] equals dict2["id"] 
select dict1.Concat(          //concatenates 2 dictionaries together 
      dict2.Where(kv => !dict1.ContainsKey(kv.Key)) //chooses non-repeating keys 
     ).ToDictionary(kv => kv.Key, kv => kv.Value)  //gets a new dictionary from that 

如果源的长度不同join只会选择这些字典，其中id s在第一个来源。如果你想获得的所有id S，你无论有两个来源的数据，你可以使用DefaultIfEmpty

from dict1 in firstSourceData 
join tempDict2 in secondSourceData 
on dict1["id"] equals tempDict2["id"] into joined 
from dict2 in joined.DefaultIfEmpty(new Dictionary<string, object>()) //make a new dictionary if there's none 
select dict1.Concat(
      dict2.Where(kv => !dict1.ContainsKey(kv.Key)) 
     ).ToDictionary(kv => kv.Key, kv => kv.Value) 

如果你想从字典都不管id s请参阅this问题。