具有最大日期的 IN 子句的 LINQ 表达式

Question

我有以下查询需要写成 LINQ

select * from sales s 
where area in ('f1','f2','f3') and sdate =(select max(sdate) from sales ss where ss.area= s.area)

我对最大日期感到困惑。

我当前的代码：

        var maxDate = (from A in _context.sales
                       where inputArray.Contains(A.area)
                       select A.sdate)
                       .Max();
        var Model =
        (from A in _context.sales
         where inputArray.Contains(A.area) && A.sdate== maxDate  
         select ...)

Answer 1

谈论

sdate =(select max(sdate) from sales ss where ss.area= s.area)

条件，或更准确地说

s.sdate = (select max(ss.sdate) from sales ss where ss.area = s.area)

您可以使用几乎相同的子查询语法 - 只是 Max 应该在 LINQ 查询语法 之外，或者只对那部分使用 LINQ 方法语法，例如要么

from s in _context.sales
where inputArray.Contains(s.area)
    && s.sdate == (from ss in _context.sales where ss.area == s.area select  ss.sdate).Max()

或

where inputArray.Contains(s.area)
    && s.sdate == _context.sales.Where(ss => ss.area == s.area).Max(ss => ss.sdate)

Answer 2

表达式 x => list.Contains(x) 将转换为 IN sql 查询

var list = new List<string>{"f1","f2","f3"};
var query = context.Sales
            .Where(x => list.Contains(x.Area))
            .GroupBy(x => x.Area)
            .Select(x => x.OrderByDescending(y=>y.sDate).First());