如何使用 Linq 加入两个实体

Question

我有两个模型 RP 和 RPHistory 如下所示，它们都包含相同的数据，我如何将它们结合起来从两者中创建单个列表数据？

 public class RP: 
    {
        public int ID { get; set; }
        public int RPID { get; set; }
        public string Name { get; set; }
        public int ProductID { get; set; }
    }

我有第二个模态

 public class RPHistory: 
    {
        public int ID { get; set; }
        public int RPID { get; set; }
        public string Name { get; set; }
        public int ProductID { get; set; }
    }

我有这段代码可以从 RP 获取数据：

var RPs = await Context.RP.Where(b => b.ProductID  == request.ID).ToListAsync();

如何加入更新上述代码以包含 RPHistory？

Answer 1

尝试以下方式：

var RPs = await Context.RP.Where(b => b.ProductID  == request.ID)
                          .Select(x=> new {
                                           x.ID, 
                                           x.RPID, 
                                           x.Name, 
                                           x.ProductID, 
                                           History = Context.RPHistory
                                                            .Where(y=> y.RPID == x.RPID)
                                                            .ToList() //Note nested Select 
                                                                      //assuming List and 
                                                                      //there can be more 
                                                                      //than one entry
                                           }
                                  ).ToListAsync();

编辑：

如果你想要一个具体的类，就这样做：

public class RpWithHistory {
  public int ID;
  public int RPID;
  public string Name;
  public int ProductID;
  public List<RPHistory> History;
}

// Then in your code:

var RPs = await Context.RP.Where(b => b.ProductID  == request.ID)
                              .Select(x=> new RpWithHistory {
                                               ID = x.ID, 
                                               RPID = x.RPID, 
                                               Name = x.Name, 
                                               ProductID = x.ProductID, 
                                               History = Context.RPHistory
                                                                .Where(y=> y.RPID 
                                                                        == x.RPID)
                                                                .ToList()
                                               }
                                      ).ToListAsync();