C# trouver tous les Éléments d'une Liste<Item>

   var types = (from p in productsList
               from t in p.Types
               select t).Distinct(new TypeComparerById());
   var productsGrouped = (from t in types
                         select new 
                         {
                          Type = t,
                          ProductsPerType = productsList.Where(p=>p.Types.Any(pt=>pt.Id == t.Id))
                         }).ToList();

Modifier


Ronald Wildenberg a justement relevé que l'appel Distinct() ne fonctionne que si les instances sont les mêmes. Pour corriger ce je mettre à jour avec la mise en

public class TypeComparerById : IEqualityComparer<Type>
{
    public bool Equals(Type t1, Type t2)
    {
        if (t1.Id == t2.Id)
        {
            return true;
        }
        else
        {
            return false;
        }
    }  

    public int GetHashCode(Type t)
    {
        return t.Id.GetHashCode();      
    }
}

Vous devriez choisir sa réponse comme correcte (bien que le suivant est correct aussi)

OriginalL'auteur Adrian Iftode

Alors j'essaie de recherche Comme cette

Pour que vous n'avez pas besoin d'un dictionnaire...

Code:

var productsList = new List<Product>();
productsList.Add(new Product { Id = 1, Name = "p1", Types = new List<Type>() { new Type() { Id = 1, Name = "ptype1" }, new Type() { Id = 2, Name = "ptype2" } } });
productsList.Add(new Product { Id = 2, Name = "p2", Types = new List<Type>() { new Type() { Id = 1, Name = "ptype1" } } });
productsList.Add(new Product { Id = 3, Name = "p3", Types = new List<Type>() { new Type() { Id = 2, Name = "ptype2" } } });
productsList.Add(new Product { Id = 4, Name = "p4", Types = new List<Type>() { new Type() { Id = 2, Name = "ptype2" }, new Type() { Id = 3, Name = "type3" } } });
//this is an IEnumerable<Type> (types with the same Id and different name will take only the first)
var productTypesList = (from p in productsList      //for each product
from t in p.Types           //for each type in product
group t by t.Id into types  //group em by Id into types
select types.First());      //but use only the first (else this would be an IEnumerable<IGrouping<Type>>
Console.WriteLine("Types:");
//EDIT: Since Francesca had some complains, and thought having a dictionary from this is difficult, here is a one liner to do that.
//This can be done by surrounding the query above with parenthesis and adding the ToDictionary() call at the end
//I prefer not to use a dictionary unless needed and your code seems not to need it since you need to loop on product types, as stated at the end of the question
//Use this only if you need to store or pass around these values. if you do, you loose potential other properties of your types.
var prodTypeDict = productTypesList.ToDictionary(v => v.Id, v => v.Name);
foreach (var p in productTypesList)
{
Console.WriteLine(p.Id + " " + p.Name);
}
foreach (var type in productTypesList)
{
//this is an IEnumerable<Product>
var products = from p in productsList                   //for each product
where p.Types.Any(t => t.Id == type.Id)  //that has this type
select p;
Console.WriteLine("Products of type: " + type.Name);
foreach (var p in products)
{
Console.WriteLine(p.Id + " " + p.Name);
}
}

De sortie:

Types:
1 ptype1
2 ptype2
3 type3
Products of type: ptype1
1 p1
2 p2
Products of type: ptype2
1 p1
3 p3
4 p4
Products of type: type3
4 p4

OriginalL'auteur Marino Šimić