c#/linq 数据分组

Question

我有一个类似这样的产品类:

class Product
{
  public string Name;
  public int Year;
  public int Vendor;
  public int Count;
}

数据输入类似

Name Year Vendor Count

'A'  1990   1     15

'A'  1990   2     20

'A'  1998   4     5

'B'  1995   1     15

'B'  1995   2     2

我想将数据转换成一个新的结构，比如

class NewStructure
{
 public string Name;
 public int Year;
 Dictionary<int, int> Vendor_Count;
} 

Dictionary字段用来存储{Vendor, Count}对，Name和Year这对会有一个对应的字典。结果会是

Name Year Vendor Count

'A'  1990   1  15

            2  20

'A'  1998   4  5

'B'  1995   1  15

            2   2

我尝试了以下 linq 查询

from input in inputList
group inputList by new { input.Name, input.Year }
into grouping
orderby grouping.Key.Name, grouping.Key.Year
select new
{
   ProductName = grouping.Key.Name,
   OriginYear = grouping.Key.Year,
   Vendor_Count = grouping.
 } 

但我无法正确获取“Vendor_Count”。我想知道我该怎么办？

Answer 1

如果(名称、年份、供应商)的组合是唯一的，则使用此方法:

inputList.GroupBy(x => new { x.Name, x.Year })
         .Select(x => new
                      {
                          ProductName = x.Key.Name,
                          OriginYear = x.Key.Year, 
                          Vendor_Count = x.ToDictionary(y => y.Vendor
                                                        y => y.Count)
                      })
         .OrderBy(x => x.ProductName).ThenBy(x => x.OriginYear);

如果它不是唯一的，则使用它:

inputList.GroupBy(x => new { x.Name, x.Year })
         .Select(x => new
                      {
                          ProductName = x.Key.Name,
                          OriginYear = x.Key.Year, 
                          Vendor_Count = x.GroupBy(y => y.Vendor)
                                          .ToDictionary(y => y.Key,
                                                        y => y.Sum(z => z.Count))
                      })
         .OrderBy(x => x.ProductName).ThenBy(x => x.OriginYear);