在此上下文中仅支持基本类型或枚举类型 [英] Only primitive types or enumeration types are supported in this context

问题描述

所以我有这个代码：

    public int saleCount(List<Shift> shifts) {
        var query = (
            from x in database.ItemSales
            where shifts.Any(y => y.ID == x.shiftID)
            select x.SalesCount
        );
        return query.Sum();
    }

不幸的是，它抛出了这个错误：

Unfortunately, it's throwing this error:

Unable to create a constant value of type 'Shift'. 
Only primitive types or enumeration types are supported in this context.

所以这里是我定义shift的地方，这只是一个普通的实体框架代码第一个对象： p>

So here is where I define shift, which is just a normal Entity Framework Code First object:

[Table("Shifts")]
public class Shift : MPropertyAsStringSettable {
    [Key]
    [DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
    public int ID { get; set; }
    public int SiteID { get; set; }
    public string ShiftID_In_POS { get; set; }
    public DateTime ShiftDate { get; set; }
}

我猜问题是我在Linq查询中使用Shift对象。我正在Shift列表中进行任何操作。

I guess the problem is that I am using Shift object in a Linq query. And I am doing a "Any" operation on a List of "Shift".

一个可能的解决方案是将列表更改为可能的集合或其他东西，在其他地方加载一个linq查询，但签名是什么？

One possible solution is to change the List to maybe a Collection or something, afterall, I am loading it with a linq query somewhere else, but what would the signature be?

推荐答案

尝试此更改不使用在查询中收集 Shift

Try this change that does not use a collection of Shifts in the query:

public int saleCount(List<Shift> shifts) {
    var shiftIds = shifts.Select(s => s.ID).ToList();
    var query = (
        from x in database.ItemSales
        where shiftIds.Contains(x.shiftID)
        select x.SalesCount
    );
    return query.Sum();
}

这个想法是避免通过 Shift 对象到查询提供者，使用ID代替。

The idea is to avoid passing Shift objects to the query provider, using IDs instead.

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