选择单个对象及其对应的列表

Question

我有一个包含ProjectID及其详细信息的类，如下所示，我想从SQL Server中检索列表详细信息。我正在努力将行列表转换为ProjectModel。 我在下面尝试过，并引用了各种来源，但没有运气。我想编写获取列表的代码，而不是 BuildAutoCompleteList（PTO）。

我是否需要使用groupby来获得结果。

课程

public class ProjectModel
{
    public string ProjectName { get; set; }
    public Guid ProjectID { get; set; }
    public IEnumerable<SegmentModel> Segments { get; set; }        
}

public class SegmentModel
{
    public DateTime? StartDate { get; set; }
    public DateTime? EndDate { get; set; }        
    public string MileStone { get; set; }        
}
public class ProjectMilestone
{
    public string ProjectName { get; set; }
    public Guid ProjectID { get; set; }
    public DateTime? StartDate { get; set; }
    public DateTime? EndDate { get; set; }
    public string MileStone { get; set; }
    public ProjectMilestone() { }
}

实体

var collection = _db.GetReportMilestones().Join(_db.GetReports(), RM => RM.ReportId, R => R.Id,
                (RM, R) => new { RM, R }).
                Join(_db.GetProjects(), P => P.R.ProjectId, PR => PR.Id, (P, PR) => new { P, PR }).Where(M => M.P.R.StateId == 1)
                .Select(PTO => new ProjectTimelineModel
                {
                    ProjectName = PTO.PR.Name,
                    ProjectID = PTO.PR.Id,
                    Segments = BuildAutoCompleteList(PTO)
                }).ToList();

下面是我的尝试，会引发错误。

 var collection = _db.GetReportMilestones().Join(_db.GetReports(), RM => RM.ReportId, R => R.Id,
            (RM, R) => new { RM, R }).
            Join(_db.GetProjects(), P => P.R.ProjectId, PR => PR.Id, (P, PR) => new { P, PR }).Where(M => M.P.R.StateId == 1)
            .Select(PTO => new ProjectMilestone
            {
                ProjectName = PTO.PR.Name,
                ProjectID = PTO.PR.Id,
                StartDate = PTO.P.RM.ScheduledDate,
                EndDate = PTO.P.RM.PassedDate,
                MileStone = PTO.P.RM.Name
            }).ToList();

        var results = collection.OrderBy(n => n.ProjectName);

        var groupbyResult = results.GroupBy(n => new { n.ProjectID, n.ProjectName }).Select(x => new ProjectTimelineModel()
        {
            ProjectID = x.Key.ProjectID,
            ProjectName = x.Key.ProjectName,
            Segments = x.GroupBy(n => n.ProjectID)

        }).ToList();