LINQ的All的方法

方法All返回布尔值bool，判断集合中是否所有元素都满足某一条件，通俗一点说，就是每一个元素，均符合同一个条件，它才返回真，不然返回假。

举列，创建一个model:

source code:

namespace Insus.NET.Models
{
   public class Book
    {
        public string Publishing { get; set; }

        public string ISBN { get; set; }

        public DateTime PublicationDate  { get; set; }
    }
}

在ASP.NET MVC的视图片中，实现：

source code:

 Book[] books = { new Book { Publishing = "商务出版社",ISBN="",PublicationDate=Convert.ToDateTime("2016-04-13")},
                             new Book { Publishing = "中华出版社",ISBN="",PublicationDate=Convert.ToDateTime("2016-01-19")},
                             new Book { Publishing = "海天出版社",ISBN="",PublicationDate=Convert.ToDateTime("2016-03-22")},
                             new Book { Publishing = "云贵出版社",ISBN="",PublicationDate=Convert.ToDateTime("2016-02-22")}
            };

            IEnumerable<Book> query = from bk in books
                                      where books.All(b => b.PublicationDate > Convert.ToDateTime("2016-01-01"))
                                      select bk;

            query.ForEach(delegate (Book b)
            {
                WriteLiteral(string.Format("publishing: {0}; ISBN: {1}; Publication Date: {2} <br />",
                                            b.Publishing,
                                            b.ISBN,
                                            b.PublicationDate.ToString("yyyy-MM-dd")));
            });

更好理解，修改一下：