策略设计模式问题委托c

Question

我很难使用委托和策略模式。有两个奖学金。我想随便挑选一个符合奖学金标准的学生。它不起作用。对于if(pickup(行，它显示错误"无法将类型"StudentGroup.Ppickup"隐式转换为"bool"。如何解决？非常感谢。还有其他错误吗？谢谢

public class Student
{
public string name;
public int year; //1 to 4
public double gpa; //0-4.0
}
public class StudentGroup
{
private List<Student> students = new List<Student>();
private Random rnd = new Random();
public delegate bool Pickup(Student x);
public void AddStudent(string name, int year, double gpa)
{
Student s = new Student();
s.name = name;
s.year = year;
s.gpa = gpa;
students.Add(s);
}
public Student PickFor(Pickup pickup)
{
List<Student> candidates = new List<Student>();
foreach (Student s in students)
{
if (pickup)
candidates.Add(s);
}
if (candidates.Count > 0)
return candidates[rnd.Next(candidates.Count)];
else
return null;
}
}
public class Program
{
public static void Main()
{
StudentGroup sg = new StudentGroup();
sg.AddStudent("Peter", 2, 3.2);
Student candidate1 = sg.PickFor(s => s.gpa >= 3.8);
Student candidate2 = sg.PickFor(s => s.gpa >= 3.0 && s.year == 1);
}
}

Answer 1

您的Pickup委托需要一个Student类型的参数，因此请确保在if语句中传递一个，并确保您正在对委托执行某些操作。

if (pickup(s))
candidates.Add(s);