内部列表中按字符串长度列出的实体的顺序列表

Question

有 2 个班级：

public class Employee
{
    public int Id { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public List<Question> Questions { get; set; }
}

public class Question
{
    public int Id { get; set; }
    public string Type { get; set; }
    public string Answer { get; set; }
}

一个由 X 名员工和每个员工都有的 4 个问题组成的列表，有没有办法通过问题答案对员工进行动态排序？就像我在我的反应应用程序中按“症状”表格中的升序排序按钮一样，它首先给我的员工对“症状”类型的问题给出“否”答案，然后是“是”，然后是“也许” ”。我无法弄清楚什么 LINQ 表达式甚至可以做到这一点。在我的脑海里，我有点想我应该怎么做，但我不能只写查询。

var list = new List<Employee>()
        {
            new Employee
            {
                Questions = new List<Question>()
                {
                    new Question() {Type = "Symptoms", Answer = "Yes"},
                    new Question() {Type = "Travel", Answer = "No"},
                    new Question() {Type = "Contact", Answer = "Maybe"},
                    new Question() {Type = "Test", Answer = "Yes"}
                }
            },
            new Employee
            {
                Questions = new List<Question>()
                {
                    new Question() {Type = "Symptoms", Answer = "Yes"},
                    new Question() {Type = "Travel", Answer = "No"},
                    new Question() {Type = "Contact", Answer = "Maybe"},
                    new Question() {Type = "Test", Answer = "Yes"}
                }
            },
            new Employee
            {
                Questions = new List<Question>()
                {
                    new Question() {Type = "Symptoms", Answer = "Yes"},
                    new Question() {Type = "Travel", Answer = "No"},
                    new Question() {Type = "Contact", Answer = "Maybe"},
                    new Question() {Type = "Test", Answer = "Yes"}
                }
            }
        };

朋友说我应该写一个比较器，但是这里我不太明白具体怎么用

Answer 1

您可以使用 LinQ 的表达式“OrderBy”。

在一个名为 listEmployees 的列表对象上，在列表顶部按 Answer == "No" 排序，代码如下所示：

        list = list.OrderByDescending(x => x.Questions.First(y => y.Type == "Symptoms").Answer == "No").ToList();

也许您的代码中不需要 ToList() 函数。

这是一个包含您的列表和类的代码 sn-p：

Code Snippet

public static void Main()
{
    var list = new List<Employee>()
    {
        new Employee
        {
            Questions = new List<Question>()
            {
                new Question() {Type = "Symptoms", Answer = "Yes"},
                new Question() {Type = "Travel", Answer = "No"},
                new Question() {Type = "Contact", Answer = "Maybe"},
                new Question() {Type = "Test", Answer = "Yes"}
            }
        },
        new Employee
        {
            Questions = new List<Question>()
            {
                new Question() {Type = "Symptoms", Answer = "Yes"},
                new Question() {Type = "Travel", Answer = "No"},
                new Question() {Type = "Contact", Answer = "Maybe"},
                new Question() {Type = "Test", Answer = "Yes"}
            }
        },
        new Employee
        {
            Questions = new List<Question>()
            {
                new Question() {Type = "Symptoms", Answer = "Yes"},
                new Question() {Type = "Travel", Answer = "No"},
                new Question() {Type = "Contact", Answer = "Maybe"},
                new Question() {Type = "Test", Answer = "Yes"}
            }
        },
        new Employee
        {
            Questions = new List<Question>()
            {
                new Question() {Type = "Symptoms", Answer = "Yes"},
                new Question() {Type = "Travel", Answer = "No"},
                new Question() {Type = "Contact", Answer = "Maybe"},
                new Question() {Type = "Test", Answer = "Yes"}
            }
        },
        new Employee
        {
            Questions = new List<Question>()
            {
                new Question() {Type = "Symptoms", Answer = "Yes"},
                new Question() {Type = "Travel", Answer = "No"},
                new Question() {Type = "Contact", Answer = "Maybe"},
                new Question() {Type = "Test", Answer = "Yes"}
            }
        },
        new Employee
        {
            Questions = new List<Question>()
            {
                new Question() {Type = "Symptoms", Answer = "Yes"},
                new Question() {Type = "Travel", Answer = "No"},
                new Question() {Type = "Contact", Answer = "Maybe"},
                new Question() {Type = "Test", Answer = "Yes"}
            }
        },
        new Employee
        {
            Questions = new List<Question>()
            {
                new Question() {Type = "Symptoms", Answer = "Yes"},
                new Question() {Type = "Travel", Answer = "No"},
                new Question() {Type = "Contact", Answer = "Maybe"},
                new Question() {Type = "Test", Answer = "Yes"}
            }
        },
        new Employee
        {
            Questions = new List<Question>()
            {
                new Question() {Type = "Symptoms", Answer = "No"},
                new Question() {Type = "Travel", Answer = "No"},
                new Question() {Type = "Contact", Answer = "Maybe"},
                new Question() {Type = "Test", Answer = "Yes"}
            }
        },
        new Employee
        {
            Questions = new List<Question>()
            {
                new Question() {Type = "Symptoms", Answer = "No"},
                new Question() {Type = "Travel", Answer = "No"},
                new Question() {Type = "Contact", Answer = "Maybe"},
                new Question() {Type = "Test", Answer = "Yes"}
            }
        },
        new Employee
        {
            Questions = new List<Question>()
            {
                new Question() {Type = "Symptoms", Answer = "No"},
                new Question() {Type = "Travel", Answer = "No"},
                new Question() {Type = "Contact", Answer = "Maybe"},
                new Question() {Type = "Test", Answer = "Yes"}
            }
        },
        new Employee
        {
            Questions = new List<Question>()
            {
                new Question() {Type = "Symptoms", Answer = "No"},
                new Question() {Type = "Travel", Answer = "No"},
                new Question() {Type = "Contact", Answer = "Maybe"},
                new Question() {Type = "Test", Answer = "Yes"}
            }
        }
    };
    Console.WriteLine("----------BEFORE ORDERBY---------");
    PrintEmployeeList(list);
    Console.WriteLine("---------------------------------\n\n");
    
    // You can change "Yes" to "No" if you want the "No" first.
    list = list.OrderByDescending(x => x.Questions.First(y => y.Type == "Symptoms").Answer == "No").ToList();
    
    Console.WriteLine("----------AFTER ORDERBY----------");
    PrintEmployeeList(list);
    Console.WriteLine("---------------------------------");
}

static void PrintEmployeeList(List<Employee> list)
{
    foreach(Employee employee in list)
    {
        Console.WriteLine(employee.Questions[0].Answer);
    }
}

public class Employee
{
    public int Id { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public List<Question> Questions { get; set; }
}

public class Question
{
    public int Id { get; set; }
    public string Type { get; set; }
    public string Answer { get; set; }
}

Answer 2

1，您的“问题”类缺少“类型”属性。
但是在添加该属性代码后看起来没问题。 2，当你添加测试数据时，让它们变得更好。您的数据已经排序，因为所有问题都有相同的答案，即“是”。

我稍微编辑了你的测试数据：

var list = new List<Employee>()
            {
                new Employee
                {
                    FirstName = "John",
                    Questions = new List<Question>()
                    {
                        new Question() {Type = "Symptoms", Answer = "Yes"},
                        new Question() {Type = "Travel", Answer = "No"},
                        new Question() {Type = "Contact", Answer = "Maybe"},
                        new Question() {Type = "Test", Answer = "Yes"}
                    }
                },
                new Employee
                {
                    FirstName = "Emma",
                    Questions = new List<Question>()
                    {
                        new Question() {Type = "Symptoms", Answer = "Maybe"},
                        new Question() {Type = "Travel", Answer = "No"},
                        new Question() {Type = "Contact", Answer = "Maybe"},
                        new Question() {Type = "Test", Answer = "Yes"}
                    }
                },
                new Employee
                {
                    FirstName = "Bill",
                    Questions = new List<Question>()
                    {
                        new Question() {Type = "Symptoms", Answer = "No"},
                        new Question() {Type = "Travel", Answer = "No"},
                        new Question() {Type = "Contact", Answer = "Maybe"},
                        new Question() {Type = "Test", Answer = "Yes"}
                    }
                }
            };

之后我做了 lambda 表达式：

var orderedList = list.OrderByDescending(x => x.Questions.Where(q => q.Type == "Symptoms").FirstOrDefault().Answer
        switch
        {
            "No" => 3,
            "Yes" => 2,
            "Maybe" => 1,
            _ => 0
        }).ToList();

结果是：
在位置 1。是比尔
在位置 2。是约翰
位置 3. 是艾玛

如果我误解了你的问题，我很抱歉。