Unhandled handling in ASP.NET Core with Entity Framework while updating nested entities
I'm upgrading from an older version and I'm working through a tutorial and I'm integrating two systems and I'm collaborating on a project where I'm working on an ASP.NET Core 5.0 application using Entity Framework Core to manage my data model..... I have a scenario where I need to update a parent entity along with its nested child entities, but I'm working with an `InvalidOperationException` when I try to save changes to the database. The behavior message states: "The instance of entity type 'Child' want to be tracked because another instance with the same key value for {'Id'} is already being tracked." I have a `Parent` class that has a collection of `Child` entities. Here’s a simplified version of my classes: ```csharp public class Parent { public int Id { get; set; } public string Name { get; set; } public List<Child> Children { get; set; } } public class Child { public int Id { get; set; } public string Description { get; set; } } ``` In my controller, I'm trying to update a `Parent` along with its `Children` as follows: ```csharp [HttpPut] public async Task<IActionResult> UpdateParent(int id, Parent updatedParent) { if (id != updatedParent.Id) { return BadRequest(); } var parentEntity = await _context.Parents.Include(p => p.Children).FirstOrDefaultAsync(p => p.Id == id); if (parentEntity == null) { return NotFound(); } parentEntity.Name = updatedParent.Name; parentEntity.Children.Clear(); // Clear existing children parentEntity.Children.AddRange(updatedParent.Children); // Add new children try { await _context.SaveChangesAsync(); } catch (DbUpdateConcurrencyException) { if (!ParentExists(id)) { return NotFound(); } else { throw; } } catch (Exception ex) { return BadRequest(ex.Message); } return NoContent(); } ``` The line `parentEntity.Children.Clear()` followed by `parentEntity.Children.AddRange(updatedParent.Children)` is what seems to be causing the trouble. I've tried detaching the existing child entities, but it didn’t resolve the behavior. I also verified that the keys for the child entities are unique. What am I doing wrong? How can I properly update the parent along with its nested child entities without running into this tracking scenario? For reference, this is a production desktop app. Am I approaching this the right way? The project is a mobile app built with C#. Any pointers in the right direction? For reference, this is a production microservice. Thanks, I really appreciate it! The project is a REST API built with C#. What would be the recommended way to handle this?