Add or Update child entities when updating a parent entity in Entity Framework Core

In a new project we are using Entity Framework Core instead of EntityFramework 6.2.0. Works good but it causes a problem when updating a parents children while also inserting new children.

Example:

Current model:

public class Profile
{

    public Profile()
    {
        Interests = new List<Interest>();
    }

    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int Id { get; set; }

    public ICollection<Interest> Interests { get; set; }

}

public class Interest
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int Id { get; set; }

    public string Name { get; set; }

}

Code to add or update children in Entity Framework, worked fine in EntityFramework 6.2.0

//Interests
//Delete children
foreach (var existingChild in dbProfile.Interests.ToList())
{
    if (!profile.Interests.Any(c => c.Name == existingChild.Name))
        db.Interests.Remove(existingChild);
}

//Update and Insert children
foreach (var childModel in profile.Interests)
{
    var existingChild = dbProfile.Interests
        .Where(c => c.Name == childModel.Name)
        .SingleOrDefault();

    if (existingChild != null)
    {
        // Update child
        childModel.Id = existingChild.Id;
        db.Entry(existingChild).CurrentValues.SetValues(childModel);
    }
    else
    {
        // Insert child
        var newChild = new Interest
        {
            Name = childModel.Name,
        };
        dbProfile.Interests.Add(newChild);
    }
}

Code is based on this answer:

https://stackoverflow.com/a/27177623/3850405

When using Microsoft.EntityFrameworkCore 2.2.6 this happens:

A new Interest is added with Id 0 as expected.

However if an update occurs and the following code is ran:

db.Entry(existingChild).CurrentValues.SetValues(childModel);

Every new object with Id 0 has their Id set to -2147482197. This happens even though nothing is set for the parent object, only a single child object. Why does this happen? Has something replaced the above method in EF Core?

I can solve this by removing db.Entry(existingChild).CurrentValues.SetValues(childModel); and replace it with childModel.Name = existingChild.Name;. But if the object had 20 or more properties I would not like to manually map them one by one.