Question

假设我有一个平面的对象列表，每个对象都有一个人的名字，以及他们所在的单个角色，如下所示：

        var People = new[] { 
            new PersonRole(){ Name = "Adam", Role = "R1" },
            new PersonRole(){ Name = "Adam", Role = "R2" },
            new PersonRole(){ Name = "Adam", Role = "R3" },
            new PersonRole(){ Name = "Bob", Role = "R1" },
        };

现在，有没有直接的方法可以根据名称和角色（显然）将其转换为Dictionary<string, List<string>>。我分两步完成，如下所示，但我不得不认为有更直接的方法。

Dictionary<string, List<string>> resultLookup = 
   People.Select(p => p.Name).Distinct().ToDictionary(str => str, str => new List<string>());

People.ForEach(p => resultLookup[p.Name].Add(p.Role));

谢谢！

Answer 1

Dictionary<string, List<string>> dictionary = people.GroupBy(p => p.Name).ToDictionary(g => g.Key, g => g.Select(p => p.Role).ToList());

未经测试，但我认为这应该有用......

编辑现在进行测试，确实有效。

Answer 2

这应该这样做：

var people = new[] { 
    new { Name = "Adam", Role = "R1" },
    new { Name = "Adam", Role = "R2" },
    new { Name = "Adam", Role = "R3" },
    new { Name = "Bob", Role = "R1" },
};

var r = from p in people
        group p by p.Name
        into g
        select new {
            Name = g.Key,
            Roles = g.Select(p => p.Role).ToList()
        };

var d = r.ToDictionary(k => k.Name, e => e.Roles);

Answer 3

var dict = People.ToLookup(p=>p.Name, p=>p.Role)
  .ToDictionary(it=>it.Key, it=>it.ToList());

Answer 4

 var result = People.GroupBy(a => a.Name).ToDictionary(a => a.First().Name, b => b.Select(c => c.Role).ToList());

Answer 5

People
.GroupBy( p => p.Name )
.ToDictionary( p => p.Key, p => p.Select(pr => pr.Role).ToList() )

有没有更好的LINQ查询来做到这一点？

5 个答案: