Question

I have a Product class something like:

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

Data input like

Name Year Vendor Count

'A'  1990   1     15

'A'  1990   2     20

'A'  1998   4     5

'B'  1995   1     15

'B'  1995   2     2

I want to transform the data into a new structure like

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

The Dictionary field is used to store {Vendor, Count} pair, the pair of Name and Year would have a correspodning dictionary. The result would be

Name Year Vendor Count

'A'  1990   1  15

            2  20

'A'  1998   4  5

'B'  1995   1  15

            2   2

I tried the following linq query

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.
 } 

But I can’t get the ‘Vendor_Count’ right. I wonder what should I do?

Answer 1

Something like this :

        var p1 = new Product(){Count=15, Name="A", Vendor = 1, Year = 1990};
        var p2 = new Product() { Count = 20, Name = "A", Vendor = 2, Year = 1990 };
        var p3 = new Product() { Count = 5, Name = "A", Vendor = 4, Year = 1998 };
        var p4 = new Product() { Count = 15, Name = "B", Vendor = 1, Year = 1995 };
        var p5 = new Product() { Count = 2, Name = "B", Vendor = 1, Year = 1995 };

        var inputList = new[] {p1, p2, p3, p4, p5};

        var newStructure = inputList
            .GroupBy( p => new { p.Name, p.Year } )
            .Select( g => new { g.Key.Name, g.Key.Year, VendorCount = g.ToDictionary(p => p.Vendor, p => p.Count) }
          );

Although I don’t think you can use Vendor as a dictionary key, because they are not unique as it stands