如何将Foreach语句转换为linq表达式? [英] How do I convert Foreach statement into linq expression?

问题描述

如何将下面的foreach转换为linq表达式?

how to convert below foreach into linq expression?

var list = new List<Book>();

foreach (var id in ids)
{
    list.Add(new Book{Id=id});
}

推荐答案

这很简单:

var list = ids.Select(id => new Book { Id = id }).ToList();

或者，如果您更喜欢查询语法:

Or if you prefer query syntax:

var list = (from id in ids select new Book { Id = id }).ToList();

还请注意，只有在确实需要List<Book>时才需要ToList().否则，通常最好利用Linq的惰性评估功能，并允许仅按需创建Book对象对象.

Also note that the ToList() is only necessary if you really need List<Book>. Otherwise, it's generally better to take advantage of Linq's lazy evaluation abilities, and allow the Book objects objects to only be created on demand.

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