LINQ Expression访问更多字段

Question

I am really new to using LINQ and I was wondering what I need to do to the below expression to grab extra fields

    public class Foo
    {
        public string Name {get;set;}
        public string Manufacturer {get;set;}
        public float Price {get;set;}
    }

    var result= (
        from row in dt.AsEnumerable()
        group row by row.Field<string>("NAME") into g
        select new Foo
        {
            Name = g.Key,
            Price=g.Min (x =>x.Field<float>("PRICE"))
            //Manufacturer = ????
        }
    ).ToList();

I basically need to get the Manufacturer from the MANUFACTURER field and set it's value in the object. I've tried:

    row.Field<string>("MANUFACTURER")
//and
    g.Field<string>("MANUFACTURER")

But I am having no luck accessing the field in the DataTable. Can anyone advise what I'm doing wrong please?

Answer 1

So you want to group by name. But how do you want to aggregate the manufacturers for each name-group?

Presuming that you just want to take the first manufacturer:

var result= (
    from row in dt.AsEnumerable()
    group row by row.Field<string>("NAME") into g
    select new Foo
    {
        Name = g.Key,
        Price=g.Min (x =>x.Field<float>("PRICE")),
        Manufacturer = g.First().Field<string>("MANUFACTURER")
    }
).ToList();

Maybe you instead want to concatenate all with a separator:

// ...
Manufacturer = string.Join(",", g.Select(r=> r.Field<string>("MANUFACTURER")))

Answer 2

As your logic stands you may have more than one Manufacturer if you only group by Name. To illustrate this consider the following data, which is supported by your data structure.

Example

• ProductA, ManufacturerA
• ProductA, ManufacturerB

If you group by just "ProductA" then Manufacturer is a collection of ["ManufacturerA", "ManufacturerB"]

Potential Solution

You could group by Name and Manufacturer then access both Name and Manufacturer

var result= (
  from row in dt.AsEnumerable()
  group row by new 
  { 
    row.Field<string>("NAME"), 
    row.Field<string>("MANUFACTURER") 
  }  into g
  select new Foo
  {
    Name = g.Key.Name,
    Manufacturer = g.Key.Manufacturer,
    Price=g.Min (x =>x.Field<float>("PRICE"))
  }
).ToList();

EDIT

Based on comment " I am trying to pull the name with the cheapest price and the manufacturer along with it. "

var result= (
  from row in dt.AsEnumerable()
  group row by row.Field<string>("NAME") into g
  let x = new
  {
    Name = g.Key.Name,
    Price=g.Min (x =>x.Field<float>("PRICE"))
  }
  where (row.Name == x.Name && row.Price == x.Price)
  select new Foo
  {
    Name = row.Name,
    Manufacturer = row.Manufacturer,
    Price= row.Price
  }
).ToList();