实体框架核心-如何处理相关实体的映射和保存

我有两个相关的实体，它们之间是一对多的关系，如下所示：

I have two related entity which is one-to-many relationship like below:

class parent{
 public string parentName{get;set;}
 public virtual ICollection<child> childs { get; set; }
}

class child{
  public string childName{get;set;}
  public parent parent{get;set;}
  ["ForeignKey"]
  public int parentId {get; set;}
}
/// View Model
class VMParent{
  public string parentName{get;set;}
  /// a string array contains child name
  public string[] childlist { get; set; }
}

假设我的父母当前有2个孩子，名字为：（ apple ，梨），现在我想通过网络api将其更新为包含3个子梨（苹果，橙子，香蕉），请注意，此处已删除现有子梨子 >并添加了2个新子项（橙色，香蕉），这里假设表子项中已经存在橙色，但香蕉不存在，应将其视为子表的新条目，我可以得到我从网络api主体视图模型中以字符串数组（ [ apple， orange， banana] ）的形式添加了孩子的名字的模型，例如：

Suppose my parent currently contains 2 child with name: (apple, pear), now I want to update it through web api to contain 3 child (apple, orange, banana), note here the existed child pear is removed and 2 new child(orange, banana) is added, here assume that orange is already existed in table child but banana is not, it should be considered as new entry to child table, and I can get my updated model with childs name in a string array(["apple", "orange", "banana"]) from web api body View Model like:

[HttpPut("{id}")]
public async Task<IActionResult> Update(string name, [FromBody]VMParent VMUpdateParent)
{
    if (ModelState.IsValid)
    {
        var existingParent = await _context.Parents
                            .Include(t => t.childs)
                            .SingleOrDefaultAsync(p => p.parentName == name);

        existingParent.parentName = updateParent.parentName;

        var childsToBeUpdated = updateParent.childList; /// ["apple","orange","banana"]

        /// HOW TO HANDLE or REBUILD the relationship that can
        /// 1) remove child (pear) from existingParent
        /// 2) add child "banana" to Child table
        /// 3) add childs (orange and banana) to existingParent?
        ......

        _context.Parents.Update(existingParent);
        await _context.SaveChangesAsync();

        return new NoContentResult();
    }
    return BadRequest(ModelState);
} 

是否存在诸如Entity Framework Core中SQL中的 MERGE语句？我真的很期待使用Entity Framework在真实世界中的应用程序中的更多教程...

Is there any "MERGE" statement like in SQL in Entity Framework Core? I am really looking forward to some more tutorials in real-world application with Entity Framework...