Question

我有一个来自数据库的产品列表，从这个列表中，我使用LINQ并返回电话类列表。

List<Product> products = new List<Product>
{
   new Product { ID = 1, Name = "Alcohol", Expired = false },
   new Product { ID = 2, Name = "Phone", Expired = false },
   new Product { ID = 2, Name = "Phone", Expired = false },
   new Product { ID = 3, Name = "Computer", Expired = false },
   new Product { ID = 4, Name = "Chair", Expired = false },

 };


 var results = from i in products.Where(o => o.Name == "Phone")
               select new Phones
               {
                  ID = i.ID,
                  Phone = i.Name,
                  isChild = i.Expired
               };
 //Update the isChild property
 foreach (var item in results)
 {
    item.isChild = true;
 }

public class Phones
{
    public int ID { get; set; }
    public string Phone { get; set; }
    public bool isChild { get; set; }
}

我曾经使用foreach循环更新手机列表。但问题是，当我检查结果变量时，它不会更新上述项目。

Answer 1

这是因为IEnumerable的延迟执行。尝试将结果转换为ToList以立即执行该查询：

 var results = (from i in products.Where(o => o.Name == "Phone")
           select new Phones
           {
              ID = i.ID,
              Phone = i.Name,
              isChild = i.Expired
           }).ToList();

如果你不知道 - 每次都会重新询问产品，你会使用一套新的手机。

无法更新LINQ列表

1 个答案: