How to modify IEnumerable with LINQ to avoid foreach loop?

Question

Can the following be done in LINQ as a one-liner, without using a for-loop?

IEnumerable<MyObj> MyList = EF.GetList(etc);
foreach (var row in MyList)
{
    row.uploadedAt = MyUtils.ConvertToLocalTime(row.uploadedAtUTC, clientTimezone);
}
//return MyList, which now has both dates in LocalTime and UTC

Answer 1

Reassign the list, ideally without mutating anything. This would be more consistent with the functional programming mindset of LINQ.

IEnumerable<MyObj> myList1 = EF.GetList(etc);
IEnumerable<MyObj> myList2 = myList1.Select( x => 
        new MyObj 
        {
            uploadedAt = MyUtils.ConvertToLocalTime(x.uploadedAtUTC, x.clientTimezone),
            anyOtherFields = x.anyOtherFields
        }
    ).ToList();

If constructing a MyObj is complicated and/or you really need to mutate it, you can also do this:

IEnumerable<MyObj> myList = EF.GetList(etc);
myList = myList.Select( x => {
        x.uploadedAt = MyUtils.ConvertToLocalTime(x.uploadedAtUTC, x.clientTimezone);
        return x;
    }).ToList();

But if you're going to do it that way, you may as well use the for loop.