如何在EntityFramework中按DateTime.Date进行分组
我有一个设备型号:
public class DeviceModel { public DateTime Added { get;set; } }
我想选择设备数量,按Added
日期( 不是日期和时间,但仅限日期 )分组。 我当前的实现无效,因为linq无法将DateTime.Date
转换为sql:
var result = ( from device in DevicesRepository.GetAll() group device by new { Date = device.Added.Date } into g select new { Date = g.Key.Date, Count = g.Count() } ).OrderBy(nda => nda.Date);
如何更改此查询以使其工作?
好吧,根据这个 MSDN文档,LINQ to SQL支持Date
属性,我假设Entity Framework也支持它。
无论如何,尝试这个查询(注意我正在使用TruncateTime方法,以避免重复解析日期):
var result = from device in ( from d in DevicesRepository.GetAll() select new { Device = d, AddedDate = EntityFunctions.TruncateTime(d.Added) } ) orderby device.AddedDate group device by device.AddedDate into g select new { Date = g.Key, Count = g.Count() };
希望这可以帮助。
使用EntityFunctions.TruncateTime
var result = ( from device in DevicesRepository.GetAll() group device by new { Date = EntityFunctions.TruncateTime(device.Added)} into g select new { Date = g.Key.Date, Count = g.Count() } ).OrderBy(nda => nda.Date);