Lambda expressions - set the value of one property in a collection of objects based on the value of another property in the collection - .net-4.0

Question

I'm new to lambda expressions and looking to leverage the syntax to set the value of one property in a collection based on another value in a collection
Typically I would do a loop:
class Item
{
public string Name { get; set; }
public string Value { get; set; }
}
void Run()
{
Item item1 = new Item { Name = "name1" };
Item item2 = new Item { Name = "name2" };
Item item3 = new Item { Name = "name3" };
Collection<Item> items = new Collection<Item>() { item1, item2, item3 };
// This is what I want to simplify.
for (int i = 0; i < items.Count; i++)
{
if (items[i].Name == "name2")
{
// Set the value.
items[i].Value = "value2";
}
}
}

Answer 1

LINQ is generally more useful for selecting data than for modifying data. However, you could write something like this:
foreach(var item in items.Where(it => it.Name == "name2"))
item.Value = "value2";
This first selects items that need to be modified and then modifies all of them using a standard imperative loop. You can replace the foreach loop with ForAll method that's available for lists, but I don't think this gives you any advantage:
items.Where(it => it.Name == "name2").ToList()
.ForEach(it => it.Value = "value2");
Note that you need to add ToList in the middle, because ForEach is a .NET 2.0 feature that's available only for List<T> type - not for all IEnumerable<T> types (as other LINQ methods). If you like this approach, you can implement ForEach for IEnuerable<T>:
public static void ForEach<T>(this IEnumerable<T> en, Action<T> f) {
foreach(var a in en) f(a);
}
// Then you can omit the `ToList` conversion in the middle
items.Where(it => it.Name == "name2")
.ForEach(it => it.Value = "value2");
Anyway, I'd prefer foreach loop, because that also makes it clear that you're doing some mutation - and it is useful to see this fact easily in the code.