将两种不同的类型组合到一个linq查询中并对其进行排序

Question

我有两个数据库表，我正试图从它们创建一个联合查询。它们有不同的结构：

public partial class Notes
{
public int ID { get; set; }
public int VisitID { get; set; }
public string Note { get; set; }
public DateTime PostDate { get; set; }
public decimal AcctBalance {get; set; }
}
public partial class SystemNotes
{
public int ID {get; set;}
public int VisitID {get; set;}
public int FacilityID {get; set;}
public string Note {get; set;
public DateTime NoteDate {get ;set; }
}

我想做的是最终得到一个按PostDate排序的Notes格式的所有数据的列表。到目前为止，我尝试过的是：

List<Notes> requests = new List<Notes>();
requests = _context.Notes.Where(i => i.VisitID == VisitID && i.isActive == true).ToList();
List<SystemNotes> requests_s = new List<SystemNotes>();
requests_s = _context.SystemNotes.Where(i => i.VisitID == VisitID).ToList();

var unionA = from a in requests
select new 
{
a.ID,
a.VisitID,
a.Note,
a.PostDate,
a.AcctBalance
};
var unionB = from b in requests_s
select new Notes()
{
ID = b.ID,
VisitID = (int)b.VisitID,
Note = b.Note,
PostDate = b.NoteDate,

AcctBalance = (decimal)0.00
};
List<Object> allS = (from x in unionA select (Object)x).ToList();
allS.AddRange((from x in unionB select (Object)x).ToList());

然而，PostDate不再被识别为Object中的元素，因此我无法对其进行排序。此外，它是Object格式，而不是Notes格式，这正是我发送数据的目的。我被这一点卡住了。你能帮忙吗？还是我这样做的方式总体上是错误的？

Answer 1

如果我正确理解你想要什么：

List<Notes> myNotes = new List<Notes> {
new Notes () {
ID = 1,
VisitID = 2
}
};
List<SystemNotes> mySystemNotes = new List<SystemNotes> {
new SystemNotes () {
ID = 3,
VisitID = 4
}
};

var result = myNotes.Select (mn => new { mn.ID, mn.VisitID })
.Union(mySystemNotes.Select (msn => new { msn.ID, msn.VisitID }))
.OrderByDescending(a=>a.ID);

foreach (var currentItem in result)
{
Console.WriteLine ("ID={0}; VisitID={1}", currentItem.ID, currentItem.VisitID);
}