Question

我有ListUser类对象的列表。我需要能够使用文本表达式传入String值并按该列的升序或降序排序。我所看到的使用Lambda表达式的所有内容，都具有object属性作为强类型值，如何通过添加“ first降序”作为参数来实现此目的？

代码如下

namespace SortLists
{

  class ListUser
  {
    public int id { get; set; }
    public string firstname { get; set; }
    public string lastname { get; set; }
    public string company { get; set; }
    public string phonenumber { get; set; }
  }

  class Program
  {
     static void Main(string[] args)
     {
        var user1 = new ListUser() { id = 1, firstname = "James", lastname = "Smith", company = "Code Logic", phonenumber = "01235 566 456" };
        var user2 = new ListUser() { id = 1, firstname = "Chris", lastname = "Andrews", company = "Adobe", phonenumber = "01235 566 456" };
        var user3 = new ListUser() { id = 1, firstname = "Paul", lastname = "Jones", company = "Microsoft", phonenumber = "01235 566 456" };
        var user4 = new ListUser() { id = 1, firstname = "Peter", lastname = "Williams", company = "Apple", phonenumber = "01235 566 456" };

        List<ListUser> users = new List<ListUser>()
        {
            user1, user2, user3, user4
        };
    }
  }

Answer 1

使用字典很容易。以此开始：

var sortBy = new Dictionary<string, Func<IEnumerable<ListUser>, IEnumerable<ListUser>>>()
{
    { "firstname", lus => lus.OrderBy(lu => lu.firstname) },
    { "lastname", lus => lus.OrderBy(lu => lu.lastname) },
    { "company", lus => lus.OrderBy(lu => lu.company) },
    { "phonenumber", lus => lus.OrderBy(lu => lu.phonenumber) },
};

然后您可以轻松地进行如下排序：

List<ListUser> sorted = sortBy["firstname"](users).ToList();

如果要降序执行此操作：

List<ListUser> sorted = sortBy["firstname"](users).Reverse().ToList();

Answer 2

只需像这样构建您的排序方法即可：

if(stringPassed == "firstname")
{
  List<ListUser> sortedListUser = listUser.OrderBy(p=>p.firstName).ToList();
}
else if(...) // and so on

如果要按desc顺序订购它们，只需使用LINQ的.OrderByDescending方法。另一种很酷的方法可能是将

设置为对象

string value;
string name;

并循环反射输入字符串，使其指向类中的属性，并获得所需的字符串并对其进行排序。这是打动老师哈哈的奇特方式。

Answer 3

添加对nuget包的引用：
https://www.nuget.org/packages/System.Linq.Dynamic/

在顶部添加using System.Linq.Dynamic;。
使用var usersSorted = users.AsQueryable().OrderBy("firstname ASC").ToList();

按STRING参数对C＃对象的列表进行排序

3 个答案: