在 C# 中旋转多个列答案

【问题标题】：Pivoting multiple columns in C#在 C# 中旋转多个列
【发布时间】：2016-08-22 17:15:24
【问题描述】：

我有一个需要旋转和转换的对象的 C# 列表。但我不确定如何获得预期的结果。下面的代码讨论了结构、数据和期望的结果。我知道，我需要先对数据进行分组，然后再对其进行透视。但我很困惑如何实现它。

class Program
{
    static void Main(string[] args)
    {
        List<Rev> revList = new List<Rev>();
        Rev r = new Rev { Id = 1, Name = "One", Rank = 1, Region = "Global", Revenue = 600 }; revList.Add(r);
        r = new Rev { Id = 1, Name = "One", Rank = 1, Region = "USA", Revenue = 100 }; revList.Add(r);
        r = new Rev { Id = 1, Name = "One", Rank = 1, Region = "Euro", Revenue = 200 }; revList.Add(r);
        r = new Rev { Id = 1, Name = "One", Rank = 1, Region = "APAC", Revenue = 300 }; revList.Add(r);

        r = new Rev { Id = 2, Name = "Two", Rank = 2, Region = "Global", Revenue = 500 }; revList.Add(r);
        r = new Rev { Id = 2, Name = "Two", Rank = 2, Region = "USA", Revenue = 100 }; revList.Add(r);
        r = new Rev { Id = 2, Name = "Two", Rank = 3, Region = "APAC", Revenue = 400 }; revList.Add(r);

        r = new Rev { Id = 3, Name = "Three", Rank = 2, Region = "Global", Revenue = 300 }; revList.Add(r);
        r = new Rev { Id = 3, Name = "Three", Rank = 2, Region = "USA", Revenue = 100 }; revList.Add(r);
        r = new Rev { Id = 3, Name = "Three", Rank = 3, Region = "Euro", Revenue = 200 }; revList.Add(r);

        //Should result in THIS IS THE HARD CODED RESULT WHICH TRANFORM FUNCTION SHOULD GENERATE
        List<RevExtended> resultList = new List<RevExtended>();
        RevExtended res = new RevExtended{Name = "One", Id = 1, APACRevenue = 300, ApacRank = 1, EuroRank = 1, EurpRevenue = 200, GlobalRank = 1, GlobalRevenue = 600, USARank = 1, USARevenue = 100};
        res = new RevExtended { Name = "Two", Id = 2, APACRevenue = 400, ApacRank = 3, GlobalRank = 2, GlobalRevenue = 500, USARank = 2, USARevenue = 100 };
        res = new RevExtended { Name = "Three", Id = 3, EuroRank = 3, EurpRevenue = 200, GlobalRank = 2, GlobalRevenue = 300, USARank = 2, USARevenue = 100 };
    }

    public List<RevExtended> Transform(List<Rev> revList)
    {
        List<RevExtended> resultList = new List<RevExtended>();

        var query = from rev in revList
                    group rev by rev.Id into revGroup


        return resultList;
    }
}

public class Rev
{
    public string Name { get; set; }
    public int Id { get; set; }
    public int? Revenue { get; set; }
    public int? Rank { get; set; }
    public string Region { get; set; }
}

public class RevExtended
{
    public string Name { get; set; }
    public int Id { get; set; }

    public int? GlobalRevenue { get; set; }
    public int? GlobalRank { get; set; }

    public int? USARevenue { get; set; }
    public int? USARank { get; set; }

    public int? EurpRevenue { get; set; }
    public int? EuroRank { get; set; }

    public int? APACRevenue { get; set; }
    public int? ApacRank { get; set; }
}

【问题讨论】：

标签： c# .net linq c#-4.0 pivot

【解决方案1】：

这是您可以采取的一种方法：

var pivoted =
    from d in data
    group d by new { d.Id, d.Name } into region
    let g = region.SingleOrDefault(d => d.Region == "Global") ?? new Rev()
    let u = region.SingleOrDefault(d => d.Region == "USA") ?? new Rev()
    let e = region.SingleOrDefault(d => d.Region == "Euro") ?? new Rev()
    let a = region.SingleOrDefault(d => d.Region == "APAC") ?? new Rev()
    select new RevExtended
    {
        Id = region.Key.Id,
        Name = region.Key.Name,
        GlobalRevenue = g.Revenue,
        GlobalRank = g.Rank,
        UsaRevenue = u.Revenue,
        UsaRank = u.Rank,
        EuroRevenue = e.Revenue,
        EuroRank = e.Rank,
        ApacRevenue = a.Revenue,
        ApacRank = a.Rank,
    };

如果您需要null 值而没有区域，则需要更改模型以支持它们。

public class RevExtended
{
    public int Id { get; set; }
    public string Name { get; set; }

    public int? GlobalRank { get; set; }
    public int? GlobalRevenue { get; set; }

    public int? UsaRank { get; set; }
    public int? UsaRevenue { get; set; }

    public int? EuroRank { get; set; }
    public int? EuroRevenue { get; set; }

    public int? ApacRank { get; set; }
    public int? ApacRevenue { get; set; }
}

var pivoted =
    from d in data
    group d by new { d.Id, d.Name } into region
    let g = region.SingleOrDefault(d => d.Region == "Global")
    let u = region.SingleOrDefault(d => d.Region == "USA")
    let e = region.SingleOrDefault(d => d.Region == "Euro")
    let a = region.SingleOrDefault(d => d.Region == "APAC")
    select new RevExtended
    {
        Id = region.Key.Id,
        Name = region.Key.Name,
        GlobalRevenue = g?.Revenue,
        GlobalRank = g?.Rank,
        UsaRevenue = u?.Revenue,
        UsaRank = u?.Rank,
        EuroRevenue = e?.Revenue,
        EuroRank = e?.Rank,
        ApacRevenue = a?.Revenue,
        ApacRank = a?.Rank,
    };

【讨论】：

感谢您的快速帮助。这很棒。当Rank或recomment在任何地区都不可用时，目前显示为0，如何设置为null？
@OpenStack 从所有let 行中删除?? new Rev()，然后在select 内使用g?.Revenue、g?.Rank 等。

【解决方案2】：

当您不使用 C# 6.0 时

var pivoted =
    from x in revList.ToLookup(d => new { d.Id, d.Name })
    let g = x.SingleOrDefault(d => d.Region == "Global") ?? new Rev()
    let u = x.SingleOrDefault(d => d.Region == "USA") ?? new Rev()
    let e = x.SingleOrDefault(d => d.Region == "Euro") ?? new Rev()
    let a = x.SingleOrDefault(d => d.Region == "APAC") ?? new Rev()
    select new RevExtended
    {
        Id = x.Key.Id,
        Name = x.Key.Name,
        GlobalRevenue = g.Revenue == null ? null : g.Revenue,
        GlobalRank = g.Rank == null ? null : g.Rank,
        USARevenue = u.Revenue == null ? null : u.Revenue,
        USARank = u.Rank == null ? null : u.Rank,
        EuroRevenue = e.Revenue == null ? null: e.Revenue,
        EuroRank = e.Rank == null ? null : e.Rank,
        ApacRevenue = a.Revenue == null ? null : a.Revenue,
        ApacRank = a.Rank == null ? null : a.Rank,
    };

【讨论】：

【解决方案3】：

@OpenStack，根据接受的答案的最后一部分，您有一个适用于 6.0 之前的 C# 用户的答案。你的例子不太对。有两个问题：

您的示例将始终有一个 Rev 对象，因此该对象引用永远不会为空。
如果您确实允许空值（如预期的那样），则分配逻辑不会保护您免受空值的影响。

这是 6.0 之前的 C# 版本的公认答案的等价物：

var pivoted =
    from x in revList.ToLookup(d => new { d.Id, d.Name })
    let g = x.SingleOrDefault(d => d.Region == "Global") 
    let u = x.SingleOrDefault(d => d.Region == "USA")
    let e = x.SingleOrDefault(d => d.Region == "Euro")
    let a = x.SingleOrDefault(d => d.Region == "APAC")
    select new RevExtended
    {
        Id = x.Key.Id,
        Name = x.Key.Name,
        GlobalRevenue = g == null ? null : g.Revenue,
        GlobalRank = g == null ? null : g.Rank,
        USARevenue = u == null ? null : u.Revenue,
        USARank = u == null ? null : u.Rank,
        EuroRevenue = e == null ? null: e.Revenue,
        EuroRank = e == null ? null : e.Rank,
        ApacRevenue = a == null ? null : a.Revenue,
        ApacRank = a == null ? null : a.Rank,
    };

如果您同意，您可以更新您的答案，使其正确无误（如果您愿意，可以复制并粘贴我的答案），我将删除此答案。

【讨论】：