如何解决问题“无法将表达式...转换为SQL，并且不能将其视为本地表达式." [英] How to solve issue "Could not translate expression ...into SQL and could not treat it as a local expression."

问题描述

我的代码如下:

void Main()
{
    var q = from a in Applicants
             where(a.Claims.Any())
             select a.Claims.Sum(c => c.TotalClaimAmount());


    q.Dump();
}

public static class MyExt
{
    public static decimal TotalClaimAmount(this Claim c)
    {
        var t = c.Accommodations.Sum(a => a.AmountClaimed) +
                c.MealAllowances.Sum(ma => ma.AmountClaimed) +
                c.Meals.Sum(m => m.AmountClaimed) +
                c.Mileages.Sum(mi => mi.AmountClaimed) +
                c.Others.Sum(o => o.AmountClaimed) +
                c.ParkingTransits.Sum(pt => pt.AmountClaimed) +
                c.Travels.Sum(tr => tr.AmountClaimed);

        return (decimal)t;
    }
}

当我在LinqPad中运行它时，出现以下问题:

when I run it in LinqPad get below issue:

InvalidOperationException:无法将表达式'a.Claims.Sum(c => c.TotalClaimAmount())'转换为SQL，因此无法将其视为本地表达式.

InvalidOperationException: Could not translate expression 'a.Claims.Sum(c => c.TotalClaimAmount())' into SQL and could not treat it as a local expression.

请帮帮我.非常感谢

推荐答案

在SQL中，您的自定义方法没有相应的命令.因此编译器无法翻译您的表达式.取而代之的是先获取您的物品，然后选择结果:

There is no corresponding command for your custom method in SQL. so compiler could not translate your expression. Instead first get your items,then select your results:

 var items = Applicants.Where(a => a.Claims.Any()).ToList();
 var results = items.Select(a => a.Claims.Sum(c => c.TotalClaimAmount());

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