Question

当我使用EF 6运行此方法时，学生已更新！

 public async Task Update(Student student)
        {
            context.Entry(student).State = EntityState.Modified;
            await context.SaveChangesAsync();
        }

当我使用EF 7运行此方法时，数据库中没有任何变化！

我错了什么？我不想先检索实体来更新它！

更新

我在SaveChanges周围放了一个try / catch，收到了这条错误消息：

The UPDATE statement conflicted with the FOREIGN KEY constraint "FK_Students_Schoolclasses_SchoolclassId". The conflict occurred in database "TGBData", table "dbo.Schoolclasses", column 'Id'.
The statement has been terminated.

当我将其中一个属性（例如Student.SchoolclassId）设置为外键时，将WHOLE实体状态设置为已修改时，是否存在问题？

更新2

public class Student
{
    public Student()
    {
        StudentsTests = new HashSet<StudentTest>();
        StudentsSubjects = new HashSet<SubjectStudent>();
    }

    public int Id { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public ISet<StudentTest> StudentsTests { get; set; }
    public ISet<SubjectStudent> StudentsSubjects { get; set; }
    public Schoolclass Schoolclass { get; set; }
    public int SchoolclassId { get; set; }
}

public class Schoolclass
{
    public Schoolclass()
    {
        Students = new HashSet<Student>();
        Tests = new HashSet<Test>();
    }

    public int Id { get; set; }
    public string Number { get; set; }
    public ISet<Student> Students { get; set; }
    public ISet<Test> Tests { get; set; }

    public Schoolyear Schoolyear { get; set; }
    public int SchoolyearId { get; set; }
}

当输入Update方法时，学生FirstName / LastName属性具有新值！

Answer 1

您的错误表明您的学生有SchoolclassId，并且该值在校园表中为Id的外表中不存在。

在调用SaveChanges之前检查SchoolclassId的值。很可能这个值在Schoolclasses表中不存在。

换句话说，此错误不是因为EF 6与EF 7，而是由于在相关表中找不到外键。

在EF Core与EF 6中进行更新时，EntityState.Modified的工作方式不同

1 个答案: