在 linq 查詢中添加 Max 和 Average

Question

我在下面有一個 sql 查詢：

SELECT MAX(r.Suburb), AVG(s.Longitude) AS Longitude, AVG(s.Latitude) AS Latitude 
From CafeAddress r inner join Cafe s on s.CafeId = r.CafeId
WHERE r.Region = 'Sydney'

輸出：

Bankstown   174.759541622222    -36.8552809611111

查詢應該獲取該地區的所有郊區，例如悉尼是該地區，郊區將包括 Bankstown 等。

我將如何在下面的 linq 查詢中添加最大值和平均值？ （區域 ID 是用戶輸入（字符串））

var region = from cafeAddress in _context.CafeAddress
                         join cafe in _context.Cafe on cafeAddress.CafeId equals cafe.CafeId
                         where cafeAddress.StateProvinceRegion == regionId
                         select new { StateProvinceRegion = cafeAddress.Suburb.Max(), cafe.Latitude,  cafe.Longitude };

我只能通過使用 group by 來做到這一點，但我試圖避免這種情況。

Answer 1

我認為這將變得相當接近：

var query =
    from cafeAddress in _context.CafeAddress
    join cafe in _context.Cafe on cafeAddress.CafeId equals cafe.CafeId
    where cafeAddress.StateProvinceRegion == regionId
    orderby cafeAddress.Suburb descending
    group new
    {
        cafeAddress.Suburb,
        cafe.Latitude,
        cafe.Longitude
    } by cafeAddress.StateProvinceRegion into g
    select new
    {
        StateProvinceRegion = g.First().Suburb,
        Latitude = g.Average(x => x.Latitude),
        Longitude = g.Average(x => x.Longitude),
    };

或者這個輕微的變體：

var query =
    from cafeAddress in _context.CafeAddress
    join cafe in _context.Cafe on cafeAddress.CafeId equals cafe.CafeId
    where cafeAddress.StateProvinceRegion == regionId
    orderby cafeAddress.Suburb descending
    group new
    {
        cafeAddress.Suburb,
        cafe.Latitude,
        cafe.Longitude
    } by cafeAddress.StateProvinceRegion into gs
    from g in gs.Take(1)
    select new
    {
        StateProvinceRegion = g.Suburb,
        Latitude = gs.Average(x => x.Latitude),
        Longitude = gs.Average(x => x.Longitude),
    };