分配列表时，将相关实体替换为新实体

发布于 2025-02-10 13:49:57 字数 859 浏览 0 评论 0原文

假设我有一个实体student，它具有相关的实体类。

我需要逻辑来分配新的类，它将替换现有class

我正在使用实体框架，并且这些类映射到数据库，因此当dbcontext.savechanges时（）被执行，它应该用新记录替换旧记录。

这是为此的一种伪代码 - 具有addrange（） works的版本，但具有classe = newClasses.tolist（）;>的版本， - 添加了新类，但没有删除旧的。

谁能解释为什么仅分配列表没有删除旧记录？

public class Student 
{
    public List<Class> Classes { get; set;}

    public void UpdateClassesA(ICollection<Class> newClasses)
    {
        //this just adds new classes, but doesn't remove the existing ones (when EF SaveChanges is performed)
        Classes = newClasses.ToList();
    }

    public void UpdateClassesB(ICollection<Class> newClasses)
    {
        Classes = new List<Class>();
        Classes.AddRange(newClasses);
    }
}

原文

Let's say I've got an entity Student and it has related entities Classes.

I need logic to assign new Classes that would replace existing Classes

I'm using Entity Framework, and these classes are mapped to a database, so when DbContext.SaveChanges() is executed, it should replace old records with the new ones.

Here is sort of a pseudo code for this - the version with AddRange() works, but version with Classes = NewClasses.ToList(); - adds new classes but does not remove the old ones.

Can anyone explain why just assigning a list is not removing the old records?

public class Student 
{
    public List<Class> Classes { get; set;}

    public void UpdateClassesA(ICollection<Class> newClasses)
    {
        //this just adds new classes, but doesn't remove the existing ones (when EF SaveChanges is performed)
        Classes = newClasses.ToList();
    }

    public void UpdateClassesB(ICollection<Class> newClasses)
    {
        Classes = new List<Class>();
        Classes.AddRange(newClasses);
    }
}

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