C# LINQ-按多个属性对列表进行分组，并返回具有数组成员的对象

这将是一个由两部分组成的问题

我正在尝试构建一个用于GoogleCharts API的数据结构（特别是它们的数据表）

以下是我目前的代码：

return Json.Encode(
    RMAs
    .Where(r => r.CreatedDate.Year > DateTime.Now.Year - 4) //Only grab the last 4 years worth of RMAs
    .GroupBy(r => new { Problem = r.Problem, Year = r.CreatedDate.Year, Quarter = ((r.CreatedDate.Month) / 3) })
    .Select(r => new { Problem = r.Key.Problem, Year = r.Key.Year, Quarter = r.Key.Quarter, Count = r.Count() })
);

这让我非常接近。这将得到一个类似于以下内容的数组：

{"Problem":"It broke!","Year":2012,"Quarter":2,"Count":3},
{"Problem":"It broke!","Year":2012,"Quarter":1,"Count":1}

但是，我想要的是通过“Problem”属性对数据进行进一步分组，以便每个问题的季度都是一个数组（这使得数据结构更容易迭代）。所需结构的示例：

{"Problem":"It broke!",
    {"Year":2012,"Quarter":2,"Count":3},
    {"Year":2012,"Quarter":1,"Count":1}
},
{"Problem":"Some other problem",
    {"Year":2012,"Quarter":1,"Count":31}
}

问题的第二部分：如何确保每个季度都有数据（同样，这使使用API构建数据表的迭代更加容易），即使在该季度没有出现“问题”？使用与上次相同的示例：

{"Problem":"It broke!",
    {"Year":2012,"Quarter":2,"Count":3},
    {"Year":2012,"Quarter":1,"Count":1}
},
{"Problem":"Some other problem",
    {"Year":2012,"Quarter":2,"Count":0}
    {"Year":2012,"Quarter":1,"Count":31}
}

将以下内容添加到查询中：

.GroupBy(x => x.Problem)
.ToDictionary(g => g.Key, g => g.Select(x=>new { Year=x.Year, Quarter=x.Quarter, Count = x.Count }));

必须在上面的.ToDictionary（）之前插入以下内容：

我想。。。试试看：）

但是，我建议不要采用这种方法，在客户端上创建“空”记录，以避免过度使用带宽。

感谢您的启发，并向我展示了您可以对分组使用LINQ

我已经在本地环境中对此进行了测试，LINQ确实返回了一个问题列表，该列表与一系列年/季度分组（总计数）相关。我不知道Json.Encode是否以正确的格式编码

以下LINQ应返回符合所需格式的匿名类型：

编辑：查询现在返回至少发生一个问题但未发生指定问题的季度的计数=0

var quarters = RMAs
    .Where(rma => rma.CreatedDate.Year > DateTime.Now.Year - 4)
    .GroupBy(rma => new { 
        Year = rma.CreatedDate.Year, 
        Quarter = ((rma.CreatedDate.Month) / 3) 
    });

return Json.Encode(
    RMAs
        //Only grab the last 4 years worth of RMAs
        .Where(r => r.CreatedDate.Year > DateTime.Now.Year - 4)
        // Group all records by problem     
        .GroupBy(r => new { Problem = r.Problem })
        .Select(grouping => new
            {
                Problem = grouping.Key.Problem,
                Occurrences = quarters.Select(quarter => new
                    {
                        Year = quarter.Key.Year,
                        Quarter = quarter.Key.Quarter,
                        Count = grouping
                                .GroupBy(record => new
                                {
                                    Year = record.CreatedDate.Year,
                                    Quarter = ((record.CreatedDate.Month) / 3)
                                })
                                .Where(record => 
                                    record.Key.Year == quarter.Key.Year 
                                    && record.Key.Quarter == quarter.Key.Quarter
                                ).Count()
                    }).ToArray()
            }));

更新：感谢您使用示例JSON输出进行更新：

[{"Problem":"P","Occurrences":[{"Year":2012,"Quarter":4,"Count":2},{"Year":2012,"Quarter":2,"Count":1},{"Year":2012,"Quarter":1,"Count":1}]},{"Problem":"Q","Occurrences":[{"Year":2012,"Quarter":3,"Count":1},{"Year":2012,"Quarter":2,"Count":1},{"Year":2012,"Quarter":1,"Count":1}]}]

这是JSON输出的一个示例：

[{"Problem":"P","Occurrences":[{"Year":2012,"Quarter":4,"Count":2},{"Year":2012,"Quarter":2,"Count":1},{"Year":2012,"Quarter":1,"Count":1}]},{"Problem":"Q","Occurrences":[{"Year":2012,"Quarter":3,"Count":1},{"Year":2012,"Quarter":2,"Count":1},{"Year":2012,"Quarter":1,"Count":1}]}]

---

以下是满足您所有标准的完整重述：

public static IEnumerable<DateTime> GetQuarterDates()
{
    for (DateTime quarterDate = DateTime.Now.AddYears(-4); quarterDate <= DateTime.Now; quarterDate = quarterDate.AddMonths(3))
    {
        yield return quarterDate; 
    }
}

public static void RunSnippet()
{
    var RMAs = new[] {
        new { Problem = "P", CreatedDate = new DateTime(2012, 6, 2) },
        new { Problem = "P", CreatedDate = new DateTime(2011, 12, 7) },
        new { Problem = "P", CreatedDate = new DateTime(2011, 12, 8) },
        new { Problem = "P", CreatedDate = new DateTime(2011, 8, 1) },
        new { Problem = "P", CreatedDate = new DateTime(2011, 4, 1) },
        new { Problem = "Q", CreatedDate = new DateTime(2011, 11, 11) },
        new { Problem = "Q", CreatedDate = new DateTime(2011, 6, 6) },
        new { Problem = "Q", CreatedDate = new DateTime(2011, 3, 3) }
    };

    var quarters = GetQuarterDates().Select(quarterDate => new { Year = quarterDate.Year, Quarter = Math.Ceiling(quarterDate.Month / 3.0) });

    var rmaProblemQuarters = from rma in RMAs
            where rma.CreatedDate > DateTime.Now.AddYears(-4)
            group rma by rma.Problem into rmaProblems
            select new {
                            Problem = rmaProblems.Key,
                            Quarters = (from quarter in quarters
                                        join rmaProblem in rmaProblems on quarter equals new { Year = rmaProblem.CreatedDate.Year, Quarter = Math.Ceiling(rmaProblem.CreatedDate.Month / 3.0) } into joinedQuarters
                                        from joinedQuarter in joinedQuarters.DefaultIfEmpty()
                                        select new {
                                                        Year = quarter.Year,
                                                        Quarter = quarter.Quarter,
                                                        Count = joinedQuarters.Count()
                                                   })
                       };

    string json = System.Web.Helpers.Json.Encode(rmaProblemQuarters);
    Console.WriteLine(json);
}

---

嗨，Jon，我添加了一个由代码生成的实际JSON示例。看来你和我的想法差不多。@JamieSee-谢谢！我从未使用过JSON，因此我修改了代码，将结果存储在变量中，并将其打印到控制台，以查看其结构是否正确。我没有机会看到实际的Json.Encode调用是否有效。您的答案没有完全回答这个问题？第二部分询问如何在没有任何问题的情况下返回季度信息，而您的解决方案不会这样做。更新的解决方案现在应该包括第二部分。根据示例，它不包括完全没有问题的年度/季度组合。与JonSenchyna类似，您的答案无法解决问题的第二部分。更新答案以满足空季度标准。另外，我用Linq语法而不是Linq方法调用重申了它，因为它越来越难阅读。在问题的第二部分中，您是否筛选出没有问题的年/季度组合（即年=2012，季度=3）？

[{"Problem":"P","Quarters":[{"Year":2008,"Quarter":2,"Count":0},{"Year":2008,"Quarter":3,"Count":0},{"Year":2008,"Quarter":4,"Count":0},{"Year":2009,"Quarter":1,"Count":0},{"Year":2009,"Quarter":2,"Count":0},{"Year":2009,"Quarter":3,"Count":0},{"Year":2009,"Quarter":4,"Count":0},{"Year":2010,"Quarter":1,"Count":0},{"Year":2010,"Quarter":2,"Count":0},{"Year":2010,"Quarter":3,"Count":0},{"Year":2010,"Quarter":4,"Count":0},{"Year":2011,"Quarter":1,"Count":0},{"Year":2011,"Quarter":2,"Count":1},{"Year":2011,"Quarter":3,"Count":1},{"Year":2011,"Quarter":4,"Count":2},{"Year":2011,"Quarter":4,"Count":2},{"Year":2012,"Quarter":1,"Count":0},{"Year":2012,"Quarter":2,"Count":1}]},{"Problem":"Q","Quarters":[{"Year":2008,"Quarter":2,"Count":0},{"Year":2008,"Quarter":3,"Count":0},{"Year":2008,"Quarter":4,"Count":0},{"Year":2009,"Quarter":1,"Count":0},{"Year":2009,"Quarter":2,"Count":0},{"Year":2009,"Quarter":3,"Count":0},{"Year":2009,"Quarter":4,"Count":0},{"Year":2010,"Quarter":1,"Count":0},{"Year":2010,"Quarter":2,"Count":0},{"Year":2010,"Quarter":3,"Count":0},{"Year":2010,"Quarter":4,"Count":0},{"Year":2011,"Quarter":1,"Count":1},{"Year":2011,"Quarter":2,"Count":1},{"Year":2011,"Quarter":3,"Count":0},{"Year":2011,"Quarter":4,"Count":1},{"Year":2012,"Quarter":1,"Count":0},{"Year":2012,"Quarter":2,"Count":0}]}]