分组并连接元组列表 [英] Group and concatenate List of tuples

问题描述

我有一个成对的列表(键，值)，键和值都是字符串.我想用重复的键聚合元组.

I have a list of pairs (key, val) with both key and value being strings. I want to aggregate the tuples with duplicate keys.

For (key1, val1), (key2, val2), (key3, val3), (key1, val4), (key2, val5) 

我要输出

(key1, val1+val4), (key2, val2+val5)

这是我当前的查询

var duplicates = Contents.Records.SelectMany(x => x.Users).Select(x => new { Name = x.Name, ID= x.ID}).GroupBy(x => x.ID).Select(x => new { x.Key, Names = x.Select(p=>p.Name).Aggregate((a,b) => a +","+b)}).ToArray();

但是在每个重复项的末尾，成员名称为空.

But at the end for each entry in duplicates the member Names is empty.

数据如下，每条记录都有一个列表用户.每个用户都有一个名称和一个ID. 我在做什么错了?

The data is as follows each Records has a List Users. Each user has a Name and an ID. What am I doing wrong?

推荐答案

Aggregate看起来应该可以完成.但是我从不喜欢Aggregate.语法不直观(在我看来).通常，其他方式看起来更清晰.拿这个:

Aggregate looks like it should do the job. But I've never liked Aggregate. The syntax is not intuitive (in my mind). Usually other ways look more lucid. Take this one:

Tuple<string,string>[] tuples = { 
                                    Tuple.Create("key1", "val1"), 
                                    Tuple.Create("key2", "val2"), 
                                    Tuple.Create("key3", "val3"), 
                                    Tuple.Create("key1", "val4"), 
                                    Tuple.Create("key2", "val5")
                                };
tuples.GroupBy(t => t.Item1, t => t.Item2)
      .Select(g => Tuple.Create(g.Key, string.Join("+", g)))
      .Dump(); // Linqpad output command

结果:

key1    val1+val4
key2    val2+val5
key3    val3

这篇关于分组并连接元组列表的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！