Linq to EF-不支持的功能 [英] Linq to EF - Unsupported Functions

问题描述

我正在使用由实体框架数据源支持的Linq进行查询.

I'm making a query with Linq, backed by an Entity Framework datasource.

我遇到以下错误:

LINQ to Entities无法识别方法'Double Sqrt(Double)' 方法，并且该方法不能转换为商店表达式.

LINQ to Entities does not recognize the method 'Double Sqrt(Double)' method, and this method cannot be translated into a store expression.

这是我的函数的简化版本(我的版本更复杂，并且使用ACos，sin，cos和其他C#Math类函数).

Here's a simplified version of my function (my version is more complex and uses ACos, sin, cos and other C# Math class functions).

  var objects =
            from n in context.Products.Where(p => p.r == r)
            let a = Math.Sqrt((double)n.Latitude)
            where a < 5
            orderby a
            select n;

        return objects.Take(100).ToList();

我认为问题可能与Linq to EF(和SQL数据源)与Linq to SQL相比支持的功能有限的情况有关.我对此还比较陌生，所以我不确定100％.

I think the problem may be related to the situation that Linq to EF (and a SQL datasource) has a limited set of supported function compared to Linq to SQL. I'm relatively new to this so I'm not 100% sure.

谁能给我正确方向的指针?

Can anyone give me a pointer in the right direction?

干杯

推荐答案

尝试 SquareRoot 在SqlFunctions

    var objects =
        from n in context.Products.Where(p => p.r == r)
        let a = SqlFunctions.SquareRoot((double)n.Latitude)
        where a < 5
        orderby a
        select n;

    return objects.Take(100).ToList();

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