Question

使用LiteCollection的实例方法Find（）时，我将谓词作为参数传递给它。这是Find（）方法：stus.Find(s => s.Birthday.Year <= 1996);，完整代码在这里：

Student.cs：

public class Student
{
    public ObjectId ID { get; set; }
    public string Name { get; set; }
    public int Grade { get; set; }
    public DateTime Birthday { get; set; }
}

Program.cs：

class Program
{
    static void Main(string[] args)
    {
        using (var db = new LiteDatabase("test.db"))
        {
            LiteCollection<Student> stus = db.GetCollection<Student>("students");

            List<Student> studentList = new List<Student>()
            {
                new Student() {Name = "Nguyen Hoang Nguyen", Birthday = new DateTime(1997, 6, 3), Grade = 8},
                new Student() {Name = "Nguyen Anh Tuan", Birthday = new DateTime(1997, 7, 12), Grade = 8},
                new Student() {Name = "Pham Van Hung", Birthday = new DateTime(1996, 3, 26), Grade = 9}
            };

            stus.Insert(studentList);

            var filteredStudents = stus.Find(s => s.Birthday.Year <= 1996);

            Console.WriteLine("Student who has birth year before 1996:");
            foreach (Student filteredStudent in filteredStudents)
            {
                Console.WriteLine($"- {filteredStudent.Name}, grade: {filteredStudent.Grade}");
            }

            Console.ReadKey();
            stus.Delete(_ => true);
        }
    }
}

但是filteredStudents不包含任何学生，只有"Student who has birth year before 1996:"行被打印到控制台。那么这里有什么问题吗，或者我错过了这里的东西？谢谢您阅读我的问题。

Answer 1

您不能在 liteDB

中执行此操作

您必须创建一个DateTime对象

var d = new DateTime(1996);
var filteredStudents = stus.Find(s => s.Birthday.Year <= d);

LiteDB Find（）与DateTime.Year比较没有任何结果

1 个答案: