如何将类型“System.Collections.Generic.IEnumerable<AnonymousType#1>”转换为“System.Collections.Generic.IEnumerable<>”。

Question

我需要将以下linq直接转换为List，如果我将其转换为列表，我仍然会收到我在主题上解释的错误，它说我需要将它转换为列表，但仍然存在错误，如何我可以将其转换为字符串列表吗？不使用 foreach 等额外的转换，...​​

List<string>  eventResult= (from c in DB.Events
                        where (c.m_turbine_id == turbineid.turbineID) && (c.m_time_stamp >= frmDate && c.m_time_stamp <= toDate)

                 select new EventLogPartialViewModel
                 {
                     Timestamp = c.m_time_stamp,
                     Description = c.m_event_log_description,
                     WindSpeed = c.m_wind_speed,
                     RPM = c.m_rpm,
                     Power = c.m_power
                 }).ToList().Select(x => new
                           {
                               Timestamp = x.Timestamp.ToString("dd/MM/yyyy H:mm:ss"),
                               Description = x.Description,
                               WindSpeed = x.WindSpeed,
                               RPM = x.RPM,
                               Power = x.Power
                           }).ToList().OrderByDescending(m => m.Timestamp);

上述linq的第一部分，我获取数据并转换为列表，因为我需要更改我的时间戳格式，任何帮助将不胜感激。

Answer 1

因为您需要创建带有标题的逗号分隔值列表，

//Add headers as first item
List<string>  eventResult = new List<string>(){"Timestamp,Description,WindSpeed,RPM,Power"};

//Add records
eventResult.AddRange(from c in DB.Events
                        where (c.m_turbine_id == turbineid.turbineID) && (c.m_time_stamp >= frmDate && c.m_time_stamp <= toDate)

                 select new EventLogPartialViewModel
                 {
                     Timestamp = c.m_time_stamp,
                     Description = c.m_event_log_description,
                     WindSpeed = c.m_wind_speed,
                     RPM = c.m_rpm,
                     Power = c.m_power
                 }).ToList().Select(x => 
                      x.Timestamp.ToString("dd/MM/yyyy H:mm:ss")) + "," +
                      x.Description + "," +
                      x.WindSpeed + "," +
                      x.RPM + "," +
                      x.Power

                 .ToList());

Answer 2

在 Linq 查询中，您选择了匿名复杂类型，因此您无法为其分配 List<string>。您应该使用var 来保留匿名类型的引用。

var eventResult= (from c in DB.Events
                        where (c.m_turbine_id == turbineid.turbineID) && (c.m_time_stamp >= frmDate && c.m_time_stamp <= toDate)

                 select new EventLogPartialViewModel
                 {
                     Timestamp = c.m_time_stamp,
                     Description = c.m_event_log_description,
                     WindSpeed = c.m_wind_speed,
                     RPM = c.m_rpm,
                     Power = c.m_power
                 }).ToList().Select(x => new
                           {
                               Timestamp = x.Timestamp.ToString("dd/MM/yyyy H:mm:ss"),
                               Description = x.Description,
                               WindSpeed = x.WindSpeed,
                               RPM = x.RPM,
                               Power = x.Power
                           }).OrderByDescending(m => m.Timestamp).ToList();

另外，理想的方法是为复杂类型创建一个类来处理引用，而不是使用匿名类型。