Group by Distinct使用Linq

时间:2014-07-01 12:31:17

标签: c# linq group-by distinct

我想明确地在id上合并两个或多个集合,并为每个id创建另一个属性的集合。

我有一个对象foo

public class foo
{
    public int id { get; set; }
    public string color { get; set; }
}

我有多个List<foo>,其共有 id 但颜色不同

//list 1
id = 1, color = "red"
id = 2, color = "blue"
id = 3, color = "green"
id = 1, color = "blue"
id = 2, color = "orange"
//list 2                
id = 1, color = "black"
id = 2, color = "amber"
id = 3, color = "red"
id = 4, color = "red"
id = 2, color = "silver"

我想使用linq来设计一个新的集合,该集合在id上是不同的,但是创建和颜色属性列表。

id = 1, color = { "red", "blue", "black" }
id = 2, color = { "blue", "orange", "amber", "silver" }
id = 3, color = { "green", "red" }
id = 4, color = { "red" }

问:如何用 linq

写出来

6 个答案:

答案 0 :(得分:3)

var colours = list.GroupBy(x => x.id)
                  .Select(x => new {id = x.Key, color = x.Select(y => y.color).ToList()})
                  .ToList();

这将为您提供所需结构中名为颜色的列表。

如果您希望颜色字段是逗号分隔的字符串,请将其更改为:

var colours = list.GroupBy(x => x.id)
                  .Select(x => new {id = x.Key, color = x.Select(y => y.color).ToArray().Join(",")})
                  .ToList();

答案 1 :(得分:3)

我想你想要一个Dictionary<int, List<string>>

Dictionary<int, List<string>> idColors = foos
    .GroupBy(f => f.id)
    .ToDictionary(g => g.Key, g => g.Select(f => f.color).ToList());

现在你可以用这种方式访问​​每个id的颜色:

List<string> colors = idColors[1];
Console.WriteLine(string.Join(",", colors));

答案 2 :(得分:1)

var result = List.GroupBy(g => new { g.id, g.color })
                         .Select(g => g.First())
                         .ToList();

答案 3 :(得分:1)

您可以使用下面提到的代码

var mergedList = list1.Concat(list2)
                  .GroupBy(person => person.id)
                  .Select(group => group.Aggregate(
                                     (merged, next) => merged.Merge(next)))
                  .ToList();

答案 4 :(得分:1)

我认为这就是你要找的东西:

list1.Concat(list2)
    .GroupBy(x => x.id)
    .Select(x => new foo 
                   {  
                      id = x.Key, 
                      color = string.Join(",", x.Select(g => g.color)) 
                   }).ToList();

答案 5 :(得分:1)

试试这个:

 var combinedList = list1;
 combinedList.AddRange(list2);
 var uniqueIds = combinedList.Select(p => p.id).Distinct()

 var result = new Dictionary<int, List<string>>();
 uniqueIds.ForEach(i => result.Add(i, new List<string>());
 combinedList.ForEach(i => result[i.id].Add(i.color);

我还没有对此进行测试,但我认为应该没问题...... 可能是一个更好的方法,但这应该让你现在工作!