Extension Method to assign value to a field in every item?

Question

I could have sworn that there was an extension method already built for the Queryable class that I just can't find, but maybe I'm thinking of something different.

I'm looking for something along the lines of:

IQueryable<Entity> en = from e in IDB.Entities select e;
en.ForEach(foo => foo.Status = "Complete");

en.Foreach() would essential perform:

foreach(Entity foo in en){
   foo.Status = "Complete";
}

Is this already written? If not, is it possible to write said Extension Method, preferably allowing for any LINQ Table and any Field on that table. Where is a good place to start?

Answer 1

There is a foreach on a List<>. Roughly something along these lines:

IQueryable<Entity> en = from e in IDB.Entities select e;
en.ToList().ForEach(foo => foo.status = "Complete");

Answer 2

public static void ForEach<T>(this IEnumerable<T> sequence, Action<T> action)
{
    foreach (var item in sequence)
    {
        action(item);
    }
}

Answer 3

There's nothing in the base class library. Many, many developers have this in their own common library, however, and we have it in MoreLINQ too.

It sort of goes against the spirit of LINQ, in that it's all about side-effects - but it's really useful, so I think pragmatism trumps dogma here.

One thing to note - there's really no point in using a query expression in your example. (It's not entirely redundant, but if you're not exposing the value it doesn't matter.) The select isn't doing anything useful here. You can just do:

IDB.Entities.ForEach(foo => foo.status = "Complete");

Even if you want to do a single "where" or "select" I'd normally use dot notation:

IDB.Entities.Where(foo => foo.Name == "fred")
            .ForEach(foo => foo.status = "Complete");

Only use query expressions where they actually make the code simpler :)