Question

I have a Dictionary<int, int> idsAndTypes = new Dictionary<int, int>(); and i have a

List<Product> products = new List<Product>() 

as list of products , the product class is as below

class Product
{
public int Id {get;set;}
public int Type{get;set;}

}

the dictionary idsAndTypes contains id’s and types , now i want to use a linq query on the list to update the type of products based on id’s in the dictionary….
i know the other way can be like following :

foreach (int item in idsAndTypes.Keys)
{
    Product.Where(product => product.Id == item).
      Select(product => product).ToList()[0].
      Type = idsAndTypes[item];
}

but i want to do it with a linq query to avoid the foreach loop, is there a way to do it ?
Please suggest…

Answer 1

Well, LINQ is really for querying not for updating.

There may be a way of doing it without the loop, but I think the loop is the cleanest way. However, I wouldn’t use that loop. You’ve got something which is very quick to look up, and you’re just iterating through it… but then doing a lookup (effectively) on a slow data structure in terms of lookup. I’d do this:

foreach (Product p in products)
{
    int type;
    if (idsAndTypes.TryGetValue(product.Id, out type))
    {
        p.LinkedProductType = type;
    }
}

One difference here – that will update all the products in the list with values in the dictionary; your current code will only do the first product in the list with the given ID. I hope that isn’t a problem.