How can I update an object with its children? Patch method doesn't work

I have to update my object with its child list like below:

 public class Entity1 
 { 
    int Id{get;set;} 
    ObservableCollection<Child1> ChildrenList {get;set;} 
    string Name{get;set;}
 }

public class Child1
{
    string Nome{get;set;}
    string Cognome {get;set;}
}

      

        
        
        
      

    

I applied the patch method this way:

[AcceptVerbs("PATCH", "MERGE")]
public async Task<IHttpActionResult> Patch([FromODataUri] int key, Delta<Entity1> entityDelta)
{

            if (!ModelState.IsValid)
            {
                return BadRequest(ModelState);
            }
            var entity = await Context.Entity1.FindAsync(key);
            if (entity == null)
            {
                return NotFound();
            }
            entityDelta.Patch(entity);

            try
            {
                await Context.SaveChangesAsync();
            }
            catch (DbUpdateConcurrencyException)
            {
                return NotFound();
            }
            return Updated(entity);
}

      

        
        
        
      

    

but when i try to call it from fiddler like this:

Url: http://localhost/odata4/Entity1(1)/  with patch request

Request Headers: Content-Type: application/json

Request Body: 
{
Name: "pippo2",
ChildrenList:[{
Nome: "Test",
Cognome: "Pippo"
}]
}

      

        
        
        
      

    

It gives an error in Property.isValid Property and sets this error:

Cannot apply PATCH to navigation property "ChildList" for entity type 'Entity1'.

How can I solve this? Is the patch method the correct method?