c# - LINQ to Entities 无法识别我的方法

Question

我想在 LINQ select 中将日期和时间转换为波斯语，但 linq 无法识别我的方法:

LINQ to Entities does not recognize the method 'System.String toPersianDateTime(System.DateTime)' method, and this method cannot be translated into a store expression.

如何将我的方法更改为与 LINQ 兼容？

我的方法:

public static string toPersianDateTime(DateTime dt)
{
    PersianCalendar pc = new PersianCalendar();
    string pDateTime = pc.GetYear(dt).ToString() + "/" + pc.GetMonth(dt).ToString() + "/" + pc.GetDayOfMonth(dt).ToString() + " ";
    pDateTime += pc.GetHour(dt) + ":" + pc.GetMinute(dt) + ":" + pc.GetSecond(dt);
    return pDateTime;
}

还有我的 LINQ 代码:

var result = (from ord in db.vw_orders
              where ord.uid == user.id
              orderby ord.order_date descending
              select new { ord.id,
                           date = Tools.toPersianDateTime((DateTime)ord.order_date),
                           ord.is_final, 
                           ord.status, 
                           ord.image_count, 
                           ord.order_count, 
                           ord.total_price });

Answer 1

EF 无法将您的自定义方法转换为 SQL。您可以注入(inject) .AsEnumerable() 调用以将底层上下文从 EF 更改为 Linq-to-Objects:

var result = (from ord in db.vw_orders
              where ord.uid == user.id
              orderby ord.order_date descending select ord
             )
             .AsEnumerable()
             .Select(o => new { o.id,
                                date = Tools.toPersianDateTime((DateTime)o.order_date),
                                o.is_final, 
                                o.status, 
                                o.image_count, 
                                o.order_count, 
                                o.total_price }
                    );