按列分組，并連接1列，并對串列的1列進行求和

我需要按列分組，并連接 1 列，并對 1 列進行求和。

1. 分組方式：第一個按供應商，然后按型別

2. 連接方式：月

3. 總和：NumberInvoice

這是我的代碼：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            var InputData = new List<Invoice>()
            {
                new Invoice{ Vendor = "Microsoft", NumberInvoice= 10, Type= "PC", Month = "1" },
                new Invoice{ Vendor = "Microsoft", NumberInvoice= 10, Type= "PC", Month = "2" },
                new Invoice{ Vendor = "Microsoft", NumberInvoice= 10, Type= "Surface", Month = "1" },
                new Invoice{ Vendor = "Microsoft", NumberInvoice= 20, Type= "PC", Month = "1" },
                new Invoice{ Vendor = "Microsoft", NumberInvoice= 20, Type= "PC", Month = "2" },
                new Invoice{ Vendor = "Microsoft", NumberInvoice= 30, Type= "Surface", Month = "1" },
                new Invoice{ Vendor = "IBM", NumberInvoice= 50, Type= "Network", Month = "5" },
                new Invoice{ Vendor = "IBM", NumberInvoice= 60, Type= "Graphic Card", Month = "6" }
            };

            var result = (InputData.AsEnumerable() ?? throw new InvalidOperationException()).Select(
                    x => new
                    {
                        x.Vendor,
                        x.NumberInvoice,
                        x.Type,
                        x.Month
                    }
                ).GroupBy(
                    y => new
                    {
                        y.Vendor,
                        y.NumberInvoice,
                        y.Type,
                        y.Month
                    }
                )
                .Select(
                    a => new Invoice
                    {
                        Vendor = a.Key.Vendor,
                        NumberInvoice = a.Key.NumberInvoice,
                        Type = a.Key.Type,
                        Month = a.Key.Month,
                    }
                    ).ToList();
            foreach (var item in result)
            {
                Console.WriteLine(item.Vendor " "  item.NumberInvoice   " "   item.Type   " "   item.Month);
            }
            Console.ReadKey();
        }
        public class Invoice
        {
            public string Vendor { get; set; }
            public decimal NumberInvoice { get; set; }
            public string Type { get; set; }
            public string Month { get; set; }
        }
    }
}

這是輸出

Microsoft 10 PC 1
Microsoft 10 PC 2
Microsoft 10 Surface 1
Microsoft 20 PC 1
Microsoft 20 PC 2
Microsoft 30 Surface 1
IBM 50 Network 5
IBM 60 Graphic Card 6

所需的輸出應該是這樣的：

Vendor       Type         Month    NumberInvoice
-------------------------------------------------
Microsoft    PC           1,2      60      
Microsoft    Surface      1        40   
IBM          Network      5        50     
IBM          Graphic Card 6        60      

如您所見，對于 Microsoft，第 1 個月和第 2 個月連接在一起，并對 NumberInvoice 進行求和。所以我可以完成這個輸出嗎？

uj5u.com熱心網友回復：

1. 你應該Vendor只分組Type。

2. 為. .Sum()_ NumberInvoice對于Months,.Select()和.Distinct()將不同的月份添加到串列中。

3. 將結果回傳為List<GroupedInvoice>。（創建另一個類以將其保存Months為string串列/陣列。

4. （可選）第一個.Select()對我來說是不必要的，建議被洗掉。

var result = (InputData.AsEnumerable() ?? throw new InvalidOperationException())
    .GroupBy(
        y => new
        {
            y.Vendor,
            y.Type
        }
    )
    .Select(
        a => new GroupedInvoice
        {
            Vendor = a.Key.Vendor,
            Type = a.Key.Type,
            NumberInvoice = a.Sum(x => x.NumberInvoice),
            Month = a.Select(x => x.Month).Distinct().ToArray(),
        }
    ).ToList();

public class GroupedInvoice
{
    public string Vendor { get; set; }
    public decimal NumberInvoice { get; set; }
    public string Type { get; set; }
    public string[] Months { get; set; }
}

演示@.NET Fiddle

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