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我有一组包含事务数据的对象。该数据集具有 3 级父子关系，级别为：项目 > 阶段 > 事务。对于每个项目和阶段，将有多个交易。

class CostElement
{
    string ProjectNumber { get; set; }
    string Stage { get; set; }
    string DerivedCostElement { get; set; }
    DateTime? Date { get; set; }
    decimal? Amount { get; set; }
}

我想要找到的是一个唯一的成本元素列表 ( DerivedCostElement)，其中包含了它在任何给定单个项目中使用的最大次数。即计算每个项目出现的阶段数，然后选择最大值。

到目前为止，我尝试过的是：

//count all cost elements per project
var aggregateQuery = from ce in _costElements
                     group ce by new { ce.ProjectNumber, ce.Stage, ce.DerivedCostElement }
                     into g
                     select new
                     {
                         g.Key.DerivedCostElement,
                         g.Key.ProjectNumber,
                         g.Key.Stage
                     };

//select cost elements having max count
var countQuery = from g in aggregateQuery
                 group g by new { g.DerivedCostElement, g.ProjectNumber }
                 into grp
                 select new CostElementCount
                 {
                     CostElement = grp.Key.DerivedCostElement,
                     ProjectNumber = grp.Key.ProjectNumber,
                     Count = grp.Count()
                 };

return countQuery.ToList();

这在大多数情况下有效，我最终得到了每个项目的成本要素列表和每个项目的最大出现次数。但是结果仍然是每个项目，我想要的是一个只有最大值的唯一列表。

有人可以帮我获得正确的结果吗？此外，任何有关如何更有效或更简洁地编写此内容的建议将不胜感激。

4

1 回答 1

7

我不确定如何更有效地编写前两个查询，但我认为在 return 语句之前添加以下行会得到你想要的结果。

countQuery = countQuery.OrderByDescending(x => x.Count).GroupBy(x => x.CostElement).Select(g => g.First());

或者保持语法更一致

countQuery = from cq in countQuery
             orderby cq.Count descending
             group cq by cq.CostElement
                 into grp
             select grp.First();

这是我使用的测试数据...

_costElements = new List<CostElement>();
_costElements.Add(new CostElement() { ProjectNumber = "a", Stage = "a", DerivedCostElement = "ce6" });
_costElements.Add(new CostElement() { ProjectNumber = "a", Stage = "b", DerivedCostElement = "ce1" });
_costElements.Add(new CostElement() { ProjectNumber = "a", Stage = "x", DerivedCostElement = "ce1" });
_costElements.Add(new CostElement() { ProjectNumber = "a", Stage = "b", DerivedCostElement = "ce2" });
_costElements.Add(new CostElement() { ProjectNumber = "a", Stage = "b", DerivedCostElement = "ce3" });
_costElements.Add(new CostElement() { ProjectNumber = "a", Stage = "c", DerivedCostElement = "ce3" });
_costElements.Add(new CostElement() { ProjectNumber = "a", Stage = "d", DerivedCostElement = "ce3" });
_costElements.Add(new CostElement() { ProjectNumber = "b", Stage = "e", DerivedCostElement = "ce1" });
_costElements.Add(new CostElement() { ProjectNumber = "b", Stage = "f", DerivedCostElement = "ce1" });
_costElements.Add(new CostElement() { ProjectNumber = "c", Stage = "g", DerivedCostElement = "ce1" });
_costElements.Add(new CostElement() { ProjectNumber = "c", Stage = "h", DerivedCostElement = "ce1" });
_costElements.Add(new CostElement() { ProjectNumber = "c", Stage = "h", DerivedCostElement = "ce2" });
_costElements.Add(new CostElement() { ProjectNumber = "c", Stage = "i", DerivedCostElement = "ce2" });
_costElements.Add(new CostElement() { ProjectNumber = "d", Stage = "j", DerivedCostElement = "ce2" });
_costElements.Add(new CostElement() { ProjectNumber = "d", Stage = "k", DerivedCostElement = "ce1" });
_costElements.Add(new CostElement() { ProjectNumber = "d", Stage = "l", DerivedCostElement = "ce1" });
_costElements.Add(new CostElement() { ProjectNumber = "d", Stage = "m", DerivedCostElement = "ce1" });

我想出的结果（对countQuery结果进行了一些重新排序）是......

成本元素：ce1 项目编号：d 计数：3

成本元素：ce2 项目编号：c 计数：2

成本元素：ce3 项目编号：a 计数：3

成本元素：ce6 项目编号：一个计数：1

我认为这是所有成本要素的列表，以及项目并计算每个成本要素出现最多的地方。该输出来自我添加到 CostElementCount 的 ToString()

public string ToString()
{
    return string.Format("CostElement: {0} ProjectNumber: {1} Count: {2}", CostElement, ProjectNumber, Count);
}
于 2013-11-14T10:33:02.807 回答