Question

我正在使用EF MVC。在我的模型中，我有一个要变成学生的用户，我需要为学生分配一些字段。我正在制定一种将用户批量分配给学生的方法，我需要为学生分配一些字段。这是我目前正在做的

            var students = db.Students.AsQueryable();
            var users = db.Users.Where(u => !students.Any(s => s.UserId == u.Id) ).ToList();//exclude current students from users

            Student[] filteredStudents = new Student[users.Count];
            var i = 0;

            foreach (var user in users)
            {
                filteredStudents[i] = (Student)user;
                filteredStudents[i].CreatedDate = DateTime.Now;
                filteredStudents[i].ModifiedDate = DateTime.Now;
                i++;
            }
            db.Students.AddRange(filteredStudents);

在我的学生课上

        public static explicit operator Student(User user)
        {
            Student student = new Student() { UserId = user.Id, ApplicationUser = user };
            return student;
        }

我觉得我应该缺少一些更优雅的东西。我看到过zip，但我想要类似于EF表示法的东西，例如此伪代码

var finalList = students.AssignMany(UserId = Id, this.User = User,  Users.Select(Id, User));

这可能吗？

Answer 1

通过使用ConvertAll()，您可以使用将用户带回并返回学生并将其作为参数传递的函数。 ConvertAll函数将返回学生列表。

var users = db.Users.Where(u => !students.Any(s => s.UserId == u.Id) ).ToList();//exclude current students from users

var newStudents = users.ConvertAll(new Converter<User, Student>(UserToStudent));  //newStudents will contain the converted users, to do with what you want.


......snip.....

function static Student UserToStudent(User toConvert){
    Student student = new Student(){UserId = toConvert.Id, ApplicationUser = toConvert, CreatedDate = DateTime.Now, ModifiedDate = DateTime.Now};
    return student;
}

以EF表示法对两个列表进行迭代

1 个答案: