I have some list (where T is a custom class, and class has some properties).
I would like to know how to change one or more values inside of it by using Lambda Expressions,
I'd probably go with this (I know its not pure linq), keep a reference to the original list if you want to retain all items, and you should find the updated values are in there:
foreach (var mc in list.Where(x => x.Name == "height"))
mc.Value = 30;