Question

我有一张气象站的数据记录表，我将查询结果转换为WPF ListBox。

表结构是：

日期
时间
温度
rain_today
湿度
等

我的查询工作正常：

var q = from c in db.Apr11log
                group c by c.LogDate into g
                orderby g.Key
                select new
                {
                    LogDate = g.Key,
                    MaxTemp = g.Max(c => c.Temp),
                    MinTemp = g.Min(c => c.Temp),                                             
                    Rain = g.Max(c => c.Rain_today),
                };

但是我试图得到Max Temp和Min Temp的相应时间，即

TimeMax = .....
TimeMin = .....

我用Google搜索并用谷歌搜索，但没有发现任何有用的东西。

Answer 1

var q = from c in db.Apr11log
        group c by c.LogDate into g
        orderby g.Key
        select new
        {
            LogDate = g.Key,
            MaxRow = g.OrderByDescending(c => c.Temp).Select(c => new { c.LogDate, c.Temp }).First(),
            MinRow = g.OrderBy(c => c.Temp).Select(c => new { c.LogDate, c.Temp }).First(),
            Rain = g.Max(c => c.Rain_today),
        };

或

var q = from c in db.Apr11log
        group c by c.LogDate into g
        orderby g.Key
        let maxRow = g.OrderByDescending(c => c.Temp).First()
        let minRow = g.OrderBy(c => c.Temp).First()
        select new
        {
            LogDate = g.Key,
            MaxTemp = maxRow.Temp,
            MaxTempDate = maxRow.LogDate,
            MinTemp = minRow.Temp,
            MinTempDate = minRow.LogDate,
            Rain = g.Max(c => c.Rain_today),
        };

Answer 2

let maxTemp = c.Max(c=>c.Temp)
let minTemp = c.Min(c=>c.Temp)
select new {
    LogDate = g.Key,
    MaxTemp = maxTemp,
    MinTemp = minTemp,
    MaxTime = g.FirstOrDefault(c=>c.Temp = maxTemp).Time,
    MinTime = g.FirstOrDefault(c => c.Temp = minTemp).Time,
    Rain = g.Max(c => c.Rain_today),
       };

LINQ使用相应的时间字段查找最大/最小值

2 个答案: