EntityFramework sum嵌套

一个查询中 用到了 sum , 可是返回结果的小数有很多位 , 都不准确了..类似js中的小数运算一样...不太熟悉C#,不知道这问题是因为double的关系 , 还是因为代码写的问题 , 

通过 sql server profile 获取的sql语句执行后都是没有问题的

这是我的代码:

var query = db.SupDataGreenAccount1
    .Where(lambda)
    .GroupBy( p => new{
        p.ObjPos , p.District , p.Feature
    })
    .Select(
    p => new {
　　　　 //area是 double , 数据库中是 float
        sums = p.Sum(c => (double?)c.Area ?? 0), 
        objpos = p.Key.ObjPos , 
        district = p.Key.District , 
        feature = p.Key.Feature
    });

var ss = query.ToArray();

var list = query.ToList();

这是调试中获取的数据:

这是 sql server profile 执行的sql:

SELECT 
1 AS [C1], 
[GroupBy1].[A1] AS [C2], 
[GroupBy1].[K1] AS [ObjPos], 
[GroupBy1].[K3] AS [DISTRICT], 
[GroupBy1].[K2] AS [FEATURE]
FROM ( SELECT 
    [Extent1].[ObjPos] AS [K1], 
    [Extent1].[FEATURE] AS [K2], 
    [Extent1].[DISTRICT] AS [K3], 
    SUM([Extent1].[AREA]) AS [A1]
    FROM [dbo].[Sup_Data_GreenAccount_1] AS [Extent1]
    WHERE (1 = 1) AND (( CAST(CHARINDEX([Extent1].[DISTRICT], N'保税区') AS int)) > 0)
    GROUP BY [Extent1].[ObjPos], [Extent1].[FEATURE], [Extent1].[DISTRICT]
)  AS [GroupBy1]

这是执行上面的SQL返回的结果: