C＃：有没有办法使用lambda表达式设置集合中对象的属性？

Question

I am developing a small project and I thought I could try something I don't know so I can learn something new. I have a collection of Messages, called msgs. I would like to filter only the unread ones and then set it to "read". To do that, I called the Where method with this lambda expression, I imagine I would get a list of all messages which are unread. Now I would like to set the value to "Read" (assigning 'T' to the MessageRead property). Is there a way to do that using lambda expressions?

I got to this code, but the "All" method is not what I am loking for, I just found out that it checks if all the elements in the list match this condition.

msgs.Where(message => message.MessageRead == 'F').All(message => message.MessageRead = 'T');

Thanks a lot, Oscar

Answer 1

你所追求的是一个ForEach扩展方法，请参见这里的讨论： LINQ相当于foreach for IEnumerable <T>

Answer 2

In fact if there was such a method, it wouldn't had any benefits over regular foreach statement.

Eric Lippert (senior software design engineer at Microsoft) has a good overview of this topic: “foreach” vs “ForEach”

Answer 3

What's wrong with the foreach statement? It does exactly what you need:

foreach (var msg in msgs.Where(m => m.MessageRead == 'F'))
{
    msg.MessageRead = 'T';
}