c# - LINQ 按日期间隔获取对象

Question

我正在寻找一个 LINQ 查询，它将只选择那些日期间隔不超过 20 秒的对象。例如:

AuthenticationEssay[] essays = new AuthenticationEssay[] {
    new AuthenticationEssay() { Date = DateTime.Now.AddSeconds(20), Success = false },
    new AuthenticationEssay() { Date = DateTime.Now.AddSeconds(24), Success = false },
    new AuthenticationEssay() { Date = DateTime.Now.AddSeconds(29), Success = false },
    new AuthenticationEssay() { Date = DateTime.Now.AddSeconds(38), Success = false },
    new AuthenticationEssay() { Date = DateTime.Now.AddSeconds(125), Success = false },
    new AuthenticationEssay() { Date = DateTime.Now.AddSeconds(347), Success = false },
    new AuthenticationEssay() { Date = DateTime.Now.AddSeconds(400), Success = false },
    new AuthenticationEssay() { Date = DateTime.Now.AddSeconds(422), Success = false },
    new AuthenticationEssay() { Date = DateTime.Now.AddSeconds(446), Success = false },
    new AuthenticationEssay() { Date = DateTime.Now.AddSeconds(467), Success = false }
};

我只想选择那些日期间隔不超过 20 秒的对象中第一次出现的对象。在这种情况下，查询应该只返回前 4 个对象。任何想法？ :(

更新

抱歉，我忘了说我是按降序对数组进行排序的。所以是的，数组中的位置不应该对查询有任何影响。

Answer 1

这个呢？

var query from i in Enumerable.Range(1, count - 1)
          let current = list[i]
          let previous = list[i - 1]
          // I see some empty positions in your example, nullability check
          where current != null && previous != null
          where (current.Date - previous.Date).TotalSeconds < 20
          select previous;

编辑:显然，您必须调用 First() 才能仅获取序列的第一个元素。

query.First();

编辑 2: 我刚刚了解到您正在对结果进行降序排序。在这种情况下，查询会略有不同:

var query from i in Enumerable.Range(1, count - 1)
          let current = list[i]
          let previous = list[i - 1]
          // I see some empty positions in your example, nullability check
          where current != null && previous != null
          where (previous.Date - current.Date).TotalSeconds < 20
          select current;