Linq查询以获取列表中重复ID的不同值

Question

假设这是我的会员班

class Member 
{
    public string CategoryId { get; set; }
    public string MemberName { get; set; }
    public int Distance { get; set; }
}

而且，这是清单。

var list = new List<Member>();
list.Add(new { CategoryId = "01", MemberName = "andy", Distance = 3 });
list.Add(new { CategoryId = "02", MemberName = "john", Distance = 5 });
list.Add(new { CategoryId = "01", MemberName = "mathew", Distance = 7 });
list.Add(new { CategoryId = "03", MemberName = "bakara", Distance = 2 });

任何人都可以建议逻辑/ linq查询来获取具有唯一/唯一categoryID的列表，其中各个MemberNames用逗号分隔

输出应为：

list.Add(new { CategoryId = "01", MemberName="andy,mathew"});
list.Add(new { CategoryId = "02", MemberName="john"});
list.Add(new { CategoryId = "03", MemberName="bakara"});

Answer 1

您需要按CategoryId分组，然后为每个组加入MemberName值，如下所示：

var result =
    list.GroupBy(member => member.CategoryId)
    .Select(group => new //Do you want an anonymous type or a Member object?
    {
        CategoryId = group.Key,
        MemberName = string.Join(",", group.Select(member => member.MemberName))
    })
    .ToList();