Linq，如何按ID对数据进行分组并合并该ID中的数据

Question

从数据库中我得到以下值

PlanningID = GetValue<int>(dataReader["PlanningID"]),
PlanningStatus = GetValue<string>(dataReader["PlanningStatus"]),
Private = GetValue<int>(dataReader["Private"])
Social = GetValue<int>(dataReader["Social"])

PlanningID，PlanningStatus，Private

• 1，好，10
• 1，fair，5
• 1，不好，1

我希望按planningID对这些内容进行分组，以便它看起来像这样

public class ClassResult
{
   public int planningID { get; set; }
   public List<PlanningStatus> PlanningStatus { get; set; }
}

public class PlanningStatus
{
   public string PlanningStatus { get; set; }
   public int Private { get; set; }
   public int Social{ get; set; }
}

我试过这个，但输出错了：

IEnumerable<ClassResult> classResult =
                from result in results
                group result by new
                {
                    result.PlanningID,
                    result.PlanningStatus
                } into grouping

                select new ClassResult
                {
                    PlanningID = grouping.Key.PlanningID,
                    PlanningStatus = grouping.Key.PlanningStatus,                    
                    Private = grouping.First().Private,
                    Social = grouping.First().Social
                };

return lrrResults;

说实话，我不知道该怎么做

根据以下建议更新了投影，但仍有多个计划ID，例如1

            var results =
            from result in results
            group result by result.PlanningID
            into grouping
            select new ClassResult
            {
                PlanningID = grouping.Key,                     
                PlanningStatusType = grouping.Select(item => new PlanningStatusType
                {
                    PlanningStatus = item.PlanningStatus,
                    Private = item.Private,
                    Social = item.Social,
                }).ToList(),
                LatestChange = grouping.First().LatestChange,
                WeeklyChangeType = grouping.First().WeeklyChangeType,
                Address = grouping.First().Address
            };

Answer 1

在上面的查询中，您按PlanningID和PlanningStatus分组，因此这些组每个都包含1个项目。你想要做的是：

1. 像您一样实例化新的ClassResult，但设置planningID但设置.Key（现在只是一个属性
2. 使用PlanningStatus
将分组的每个项目投影到.Select()类型的新对象

代码：

var classResult = from result in results
                  group result by result.PlanningID into grouping
                  select new ClassResult
                  {
                      PlanningID = grouping.Key,
                      PlanningStatus = grouping.Select(item => new PlanningStatus {
                          PlanningStatus = item.PlanningStatus,
                          Private = item.Private,
                          Social = item.Social
                      }).ToList()
                  };

测试了一些示例代码并运行：