Question

这是我的两张桌子：

publicParking(publicParkingID, address, latitude, longtitude, status,
              PricePerHour, maxSpaces, occupiedSpaces, freeSpaces, isOrdered)

和

parkingLot(parkingLotID, address, latitude, longtitude, status,
           PricePerHour, maxSpaces, occupiedSpaces, freeSpaces, isOrdered)

除ID外，所有列都相同。

我需要在LINQ中编写查询，返回按价格排序的表格，并将所有可用停车位publicParking / parkingLot） - status==true

表格应如下所示：

ID地址纬度经度状态

我应该联合，还是应该更改表格，以便第一列只调用ID？（而不是publicParkingID和parkingLotID）

我已经尝试过此代码，但它不起作用

var union =  
         (from lot in parkingLots
         where lot.status == true
         select lot).Union( from pub in publicParkings
         where pub.status==true
         select pub);

它给出了这个错误：

ERROR

我正在使用LINQPad5和tutorialsteacher的代码编辑器。还有其他选择吗？

Answer 1

要使用Union，两个结果序列必须包含相同的类型。在您的示例中，外部查询包含parkingLot和内部publicParking。

可以使用匿名类型解决：

var union =  
     (from lot in parkingLots
     where lot.status == true
     orderby lot.PricePerHour // don't forget ordering
     select new {
           ID = lot.parkingLotID, 
           lot.address, lot.latitude, lot.longitude, lot.status})
    .Union(from pub in publicParkings
     where pub.status==true
     orderby pub.PricePerHour // don't forget ordering
     select new {
           ID = pub.publicParkingID, 
           pub.address, pub.latitude, pub.longitude, pub.status});

但是对于进一步的数据处理可能更好的是自定义类：

public class ParkingData
{
    public int ID {get; set;}
    public string Address {get; set;}
    public double Latitude {get; set;}
    public string Longitude {get; set;}
    public bool Status {get; set;}
}

并查询：

var union =  
     (from lot in parkingLots
     where lot.status == true
     orderby lot.PricePerHour // don't forget ordering
     select new ParkingData {
           ID = lot.parkingLotID, 
           Address = lot.address, 
           Latitude = lot.latitude, 
           Longitude = lot.longitude, 
           Status = lot.status})
    .Union(from pub in publicParkings
     where pub.status==true
     orderby pub.PricePerHour // don't forget ordering
     select new {
     select new ParkingData {
           ID = pub.publicParkingID, 
           Address = pub.address, 
           Latitude = pub.latitude, 
           Longitude = pub.longitude, 
           Status = pub.status});

Query- LINQ，2表，Union

1 个答案: