LINQ to Entities 无法识别方法 'System.DateTime GetDate()' 方法，并且此方法无法转换为存储表达式

Question

几个月前我刚刚开始学习 asp.net，但遇到了一些问题。我在浏览器上收到此错误LINQ 实体无法识别System.DateTime GetDate() 方法，而此代码在Linq 中完美运行。根据我在几个论坛上阅读的内容，当Linq to Entities 无法将代码转换为 SQL 查询时会发生此错误。但我仍然无法弄清楚我的方法有什么问题。
这是具有GetDate() 方法的类

public class Cycle
{
    private DateTime _Date;

    public DateTime Date 
    { 
        get => _Date;

        set => _Date = value;
    }

    public DateTime GetDate ()
    {
        return this._Date;
    }
}

这是调用该方法的查询

var RouteList = from site in Sites
                orderby site.Community.Name ascending
                where site.Season.SeasonYear == 2019 && site.Yard.YardID == 1 && site.SiteType.SiteTypeDescription.Equals("A")
                select new Status
                {
                    Pin = site.Pin,
                    Community = site.Community.Name,

                    Cycle1 = ((from sbm in SBMs where sbm.CrewSite.SiteID == site.SiteID select new Cycle { Date = sbm.CrewSite.Crew.TodayDate }).OrderBy(x => x.Date).FirstOrDefault()).Equals(null)
                         ? (DateTime?)null : ((from sbm in SBMs where sbm.CrewSite.SiteID == site.SiteID select new Cycle { Date = sbm.CrewSite.Crew.TodayDate }).OrderBy(x => x.Date).FirstOrDefault()).GetDate()

谁能帮我看看如何调整我的方法？

Answer 1

您需要使用DbFunctions.TruncateTime() 来获取DateTime 的日期，并使用Cycle 的Date 属性而不是自定义GetDate 方法：

var RouteList = from site in Sites
                    orderby site.Community.Name ascending
                    where site.Season.SeasonYear == 2019 && site.Yard.YardID == 1 && site.SiteType.SiteTypeDescription.Equals("A")
                    select new Status
                    {
                        Pin = site.Pin,
                        Community = site.Community.Name,

                         Cycle1 = ((from sbm in SBMs where sbm.CrewSite.SiteID == site.SiteID select new Cycle { Date = DbFunctions.TruncateTime(sbm.CrewSite.Crew) }).OrderBy(x => x.Date).FirstOrDefault()).Equals(null)
                             ? (DateTime?)null : ((from sbm in SBMs where sbm.CrewSite.SiteID == site.SiteID select new Cycle { Date = DbFunctions.TruncateTime(sbm.CrewSite.Crew)}).OrderBy(x => x.Date).FirstOrDefault()).Date

...