Can you set a property in a linq query before selecting the item?

Question

Is there any way to set a property in the middle of a query?

var products = from p in Products
               let pricecalc = p.IsDiscontinued ? 0 : p.UnitPrice
               // somehow set p.Price = pricecalc
               select p;

I know i could use select new Product { .. set props here .. } but i dont want to do this.

At the moment, i am thinking i am going to have to use a foreach to do this.

Answer 1

Instead of

 let pricecalc = p.IsDiscontinued ? 0 : p.UnitPrice

Use

 let pricecalc = (p.Price = p.IsDiscontinued ? 0 : p.UnitPrice)

Answer 2

Yes, but you need an extension method:

public static TSource Apply<TSource>(this IEnumerable<TSource> source, Action<TSource> action)
    where TSource : class // wouldn't work for value types, since the action would work on a copy
{
    foreach(var item in source)
    {
        action(item);
        yield return item;
    }
}

You can then use it like this:

var products = Products.Apply(p => p.Price = p.IsDiscontinued ? 0 : p.UnitPrice);

However I wouldn't recommend doing this; Linq queries are not supposed to produce side effects. You should probably change your query to return new objects that contain the updated price.