MongoDB .NET Driver Group By Time Range 按时间分组查询

先看下一个错误的写法：

var filter = Builders<Model>.Filter.Where(r => r.Timestamp > startDate && r.Timestamp < endDate);
var result = Collection.Aggregate()
           .Match(filter)
           .Group(
               r => r.Timestamp.Minute,
               g => new
               {
                   ReceiveDate = g.Select(x => x.Timestamp).First(),
                   Count = g.Count(),
               }
           ).ToEnumerable();

错误原因：Minute分钟数在跨小时会重复，导致数据错误。

正确的写法：

DateTime startDate = new DateTime(2018, 5, 1, 0, 0, 0, DateTimeKind.Utc);
DateTime endDate = new DateTime(2018, 6, 1, 0, 0, 0, DateTimeKind.Utc);

var result = Collection.Aggregate()
  .Match(k => k.Timestamp >= startDate && k.Timestamp < endDate)
  .Group(k =>
    new DateTime(k.Timestamp.Year, k.Timestamp.Month, k.Timestamp.Day,
        k.Timestamp.Hour, k.Timestamp.Minute - (k.Timestamp.Minute % 15), 0),
    g => new { _id = g.Key, count = g.Count() }
  )
  .SortBy(d => d._id)
  .ToList();

原文：

https://devpress.csdn.net/mongodb/62fc85617e6682346618fef7.html?