需要C＃linq查询数据透视数据

Question

我有一个带有一些字段的Order表。我现在需要其中两个：PostalCode和TimeSlot。结构如下：

我需要的是一个像下面这样的结构（在C＃中需要Linq查询）。

提前致谢。

Answer 1

你可以沿着这些方向做点什么：

//taken from LinqPad. Dump() will not work anywhere else.
void Main()
{
    var source = new List<Order> {
        new Order {ZipCode = "01", TimeSlot ="A" },
        new Order {ZipCode = "02", TimeSlot ="B" },
        new Order {ZipCode = "01", TimeSlot ="B" },
        new Order {ZipCode = "01", TimeSlot ="C" }
    };

    var pivotedOrders = source.GroupBy (s => s.ZipCode)
                              .Select(o => new {
                                ZipCode = o.Key,
                                OrdersCount = o.Count(),
                                A = o.Count(x => x.TimeSlot == "A"),
                                B = o.Count(x => x.TimeSlot == "B"),
                                C = o.Count(x => x.TimeSlot == "C")
                              })
                              .Dump();
}

public class Order
{
    public string ZipCode {get; set; }
    public string TimeSlot {get; set; }
}

结果：

Answer 2

在LINQ中，您无法动态创建动态对象。您应该尝试ExpandoObject，但老实说，我没有任何经验。

我将采用的解决方案是：我将构建一个像这样的对象，而不是每个时隙都有一个属性的对象：

class PivotData
{
    public string ZipCode { get; set; }
    public int OrdersCount { get; set; }
    public Dictionary<string, int> TimeSlots {get; set;}
}

正如您所看到的，它包含一个字符串，其中键值对为string和int：字符串是时隙的名称，int是计数。

基于此对象，您可以编写LINQ代码，如下所示：

    var source = new List<Order> {
    new Order {ZipCode = "01", TimeSlot ="A" },        
    new Order {ZipCode = "01", TimeSlot ="A" },
    new Order {ZipCode = "02", TimeSlot ="B" },
        new Order {ZipCode = "01", TimeSlot ="B" },
        new Order {ZipCode = "01", TimeSlot ="C" }
    };

    var result = source
        .GroupBy(s => s.ZipCode)
        .Select(g => new PivotData
                {
                    ZipCode = g.Key,
                    OrdersCount = g.Count(),
                    TimeSlots = g.GroupBy(x => x.TimeSlot).ToDictionary(x => x.Key, x => x.Count())
                }).ToList();

    foreach(var item in result) {
        System.Console.WriteLine("ZipCode: " + item.ZipCode + " - " + "Orders count: " + item.OrdersCount);
        Console.WriteLine("Time slots:");
        foreach(var timeSlot in item.TimeSlots) {
            System.Console.WriteLine(timeSlot.Key + " - " + timeSlot.Value);
        }
        Console.WriteLine("---");
    }