Question

我正在使用LINQ执行自定义查询，该查询根据我的语句返回一个匿名类型列表：

            var currUnitFaster = (from unit in pacificRepo.Units
                                 join loc in pacificRepo.GeoLocations on new { unit.geo_location.Latitude, unit.geo_location.Longitude } equals new { loc.geo_location.Latitude, loc.geo_location.Longitude }
                                 join st in pacificRepo.UnitStatuses on unit.c_number equals st.c_number
                                 select new { 
                                    index = "0", 
                                    unit.c_number, 
                                    unit.serial_number, 
                                    unused = "0", 
                                    unit.ip_address, 
                                    unit.build_version,
                                    status = (st.status == Pacific.Domain.Entities.UnitStatus.Statuses.COMPLETE) ? "<font color=\"green\">" + st.stage + "</font>" : "<font color=\"red\">" + st.stage + "</font>", 
                                    location = (loc==null) ? "Unknown" : loc.city + ", " + loc.state_abbrv,
                                    unit.location_at_address,
                                    latitude = unit.geo_location.Latitude,
                                    longitude = unit.geo_location.Longitude
                                 }).ToList();

因此，列表中返回的每个元素都是匿名类型：

        currUnitFaster[0].ToString() ==> "{ index = 0, c_number = J0000014, serial_number = A2F0JA02, unused = 0, ip_address = 169.254.0.9, build_version = J1, status = <font color=\"green\">Link</font>, location = San Jose, CA, location_at_address = FCC, latitude = 37.390791, longitude = -121.905775 }"

我想要一个值列表，而不是一个匿名类型列表。这样：

currUnitFaster.First()[0] ==> "0"
currUnitFaster.First()[1] ==> "J0000014"
currUnitFaster.First()[2] ==> "A2F0JA02"
...

最简单的方法是什么？我知道我可以简单地创建一个列表，然后遍历currUnitFaster中的每个元素并手动将其添加到该列表中。我想知道是否有一些更清洁的转型或基于铸造的方式来做到这一点。

修改：我已接受塞尔曼的建议，将select new更改为select new object[]。 但是，我现在尝试运行查询时遇到以下异常：

Exception: {"Unable to cast the type 'System.Nullable`1[[System.Double, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]]' to type 'System.Object'. LINQ to Entities only supports casting EDM primitive or enumeration types."}

Answer 1

将select new更改为select new object[]并删除属性名称。

编辑：似乎EF抱怨演员。试试这个：

var currUnitFaster = (from unit in pacificRepo.Units
                      join loc in pacificRepo.GeoLocations on new { unit.geo_location.Latitude, unit.geo_location.Longitude } equals new { loc.geo_location.Latitude, loc.geo_location.Longitude }
                      join st in pacificRepo.UnitStatuses on unit.c_number equals st.c_number
                      select new 
                            { 
                                index = "0", 
                                unit.c_number, 
                                unit.serial_number, 
                                unused = "0", 
                                unit.ip_address, 
                                unit.build_version,
                                status = (st.status == Pacific.Domain.Entities.UnitStatus.Statuses.COMPLETE) ? "<font color=\"green\">" + st.stage + "</font>" : "<font color=\"red\">" + st.stage + "</font>", 
                                location = (loc==null) ? "Unknown" : loc.city + ", " + loc.state_abbrv,
                                unit.location_at_address,
                                latitude = unit.geo_location.Latitude,
                                longitude = unit.geo_location.Longitude
                          })
                        .ToList()
                       .Select(x => new object[] { // write all properties here like x.index, x.c_number });

Answer 2

创建一个包含所有值的类，例如：

public class MyClass {
  public int index { get; set; }
  public int c_number { get; set; }
  public string serial_number { get; set; }
  public int unused get; set; }
  public string ip_address get; set; }
  public string build_version { get; set; }
  public Status statuses { get; set; }
  public int index { get; set; }

  ...etc...
}

然后做：

var currUnitFaster = (from unit in pacificRepo.Units
                                 join loc in pacificRepo.GeoLocations on new { unit.geo_location.Latitude, unit.geo_location.Longitude } equals new { loc.geo_location.Latitude, loc.geo_location.Longitude }
                                 join st in pacificRepo.UnitStatuses on unit.c_number equals st.c_number
                                 select new MyClass { 
                                    index = 0, 
                                    c_number = unit.c_number, 
                                    serial_number = unit.serial_number, 
                                    ...etc...

                                 }).ToList();

Answer 3

问题在于

select new {

一部分。您应该通过将其更改为类似

的类型来定义所需的类型（并且它应该适合您返回的数据）

select new MyExpectedReturnType {

查询返回匿名类型列表，而不是列表值

3 个答案: