首先感谢“q107770540”等网友的帮助。
一、"Linq to object"方法实现
public List<ListMenuCatalog> GetRoomLayerBuildingLists()
{
List<ListMenuCatalog> listmenucatalogs = new List<ListMenuCatalog>();
List<RoomLayerBuilding> roomlayerbuildings = this.GetRoomLayerBuildingDatas();
//var listbybuilding = roomlayerbuildings.Distinct(r => r.BuildingNo).ToList();
[color=#FF0000]问题一:“roomlayerbuildings.Distinct(r => r.BuildingNo).ToList()”这样不对么,为什么会出现这样的错误,信息如下?
错误 1 无法将 lambda 表达式 转换为类型“System.Collections.Generic.IEqualityComparer<ServicesEntity.RoomLayerBuilding>”,因为它不是委托类型 C:\Users\Administrator\Desktop\DX4.0\Mycems.BLL\RoomLayerBuildingDatas.cs 59 62 Mycems.BLL
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//var listbybuilding = (from lb in roomlayerbuildings select roomlayerbuildings.BuildingNo).Distinct();
问题二:“from lb in roomlayerbuildings select roomlayerbuildings.BuildingNo).Distinct()”这样写不对么? 为什么会出现这样的错误,信息如下?
错误 1 “System.Collections.Generic.List<ServicesEntity.RoomLayerBuilding>”不包含“BuildingNo”的定义,并且找不到可接受类型为“System.Collections.Generic.List<ServicesEntity.RoomLayerBuilding>”的第一个参数的扩展方法“BuildingNo”(是否缺少 using 指令或程序集引用?) C:\Users\Administrator\Desktop\DX4.0\Mycems.BLL\RoomLayerBuildingDatas.cs 60 91 Mycems.BLL
return listmenucatalogs;
}
问题三:如果从“roomlayerbuildings”集合中筛选出“DpRoomNo”、“RoomName”两个属性字段不重复的的结果集,应该怎样写?
问题四:“var query3=room.Where(r=>r.DpRoomNo=="001").ToList();”返回的是一个“List”,要获取其中的值,还要将“Var query3”转化为“List”集合,然后获取第一个是么?还有其它好的方法么?
完整实体类:
public class RoomLayerBuilding : INotifyPropertyChanged
{
public RoomLayerBuilding() { }
/// <summary>
/// 房间编号
/// </summary>
public String DpRoomNo
{
get
{
return _dproomno;
}
set
{
_dproomno = value;
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs("DpRoomNo"));
}
}
/// <summary>
/// 房间名称
/// </summary>
public String RoomName
{
get
{
return _dproomname;
}
set
{
_dproomname = value;
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs("RoomName"));
}
}
/// <summary>
/// 楼层编号
/// </summary>
public String LayerNo
{
get
{
return _dplayerno;
}
set
{
_dplayerno = value;
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs("LayerNo"));
}
}
/// <summary>
/// 建筑编号
/// </summary>
public String BuildingNo