在LINQ查询方面需要帮助

Question

I have the following class:

internal class ModuleScrap
    {
        public System.DateTime ReadTime { get; set; }
        public string ScrapReason { get; set; }
        public Int16 NetScrap { get; set; }
    }

I could use some help with a LINQ query that retrieves all rows between a range of dates (that's the easy part), groups on ScrapReason and determines the sum of NetScrap for each group. I don't have much experience with grouping in LINQ.

Answer 1

Something like this, I suspect:

var query = from scrap in scraps
            where scrap.ReadTime >= minDate && scrap.ReadTime <= maxDate
            group scrap by scrap.ScrapReason into g
            select new { Reason = g.Key, Total = g.Sum(x => (int) x.NetScrap) };

Note that the int cast is because Sum isn't defined for Int16 values. An alternative is to change the grouping:

var query = from scrap in scraps
            where scrap.ReadTime >= minDate && scrap.ReadTime <= maxDate
            group (int) scrap.NetScrap by scrap.ScrapReason into g
            select new { Reason = g.Key, Total = g.Sum() };

They'll give the same results - it's just a matter of which you prefer.