如何使用 linq 按嵌套属性分组

Question

I have the following classes:

public class Split
{
    public int Id { get; set; }
    public virtual ICollection<Sort> Sorts { get; set; }
    public double Mass { get; set; }
}
public class Sort
{
    public int Id { get; set; }
    public virtual ICollection<Fraction> Fractions { get; set; }
}
public class Fraction
{
    public int Id { get; set; }
    public Method Method { get; set; }
}
public class Method
{
    public int Id { get; set; }
    public string Code { get; set; }
}

I would like to get something like the following selection/grouping of Splits for all Methods:

{Id, Mass, MethodCode} . It's fine for split to repeat for example:

1, 4.4, "Samm"
1, 4.4, "Mani"
2, 2.1, "Samm"
3, 1.5, "Pra"

In the end, I want to be able to take this list and ask something like: give me splits such that their method is "samm". If you can suggest a better structure, it's also fine. I will fetch this from SQL server, so I am looking for the most performant structure.

Answer 1

I'm not sure why you need Sort or Fraction but here's how you can get those values from that structure where splits is an IEnumerable<Split> .

var result = from s in splits
             from r in s.Sorts
             from f in r.Fractions
             select new 
             {
                 s.Id,
                 s.Mass,
                 f.Method.Code
             };

Or in method syntax

var result = splits.SelectMany(
    s => s.Sorts.SelectMany(
        r => r.Fractions.Select(
            f => new
            {
                s.Id,
                s.Mass,
                f.Method.Code
            })));