两个对象的 EF Core 保存错误取决于第二个相等的对象

Question

I have a vey long long POCO class ("FichaCliente") that I'll simplify here emphasizing the property that's an ObservableCollection:

{
  public int FichaCliente1 { get; set; }
  ...
  public int FichaClienteN { get; set; }

  public ObservableCollection<Reclamado> Reclamados { get; set; }

  public int FichaClienteN+2 { get; set; }
  ...
  public int FichaClienteN+M { get; set; }

}

The "Reclamado" class is also a relative long POCO that has another class as element, the UF class. Thus we can understand the "Reclamado" as being:

{
  public int Reclamado1 { get; set; }
  ...
  public int ReclamadoN { get; set; }

  public UF Uf { get; set; }

  public int ReclamadoN+2 { get; set; }
  ...
  public int ReclamadoN+M { get; set; }

}

Being UF class a simple POCO as follows:

{
    public int Id { get; set; }
    public string Apelido { get; set; }
    public string Descricao { get; set; }
    public string Municipio { get; set; }
}

The SAVE operation to the database is handled by just the "SaveFichaAsync" method that's as simple as:

public async void SaveFichaAsync(FichaCliente ficha)
    {
        using (var context = new DataContext(_dBService))
        {
            context.FichasClientes.Update(ficha);
            await context.SaveChangesAsync();

            return;
        }
    }

What's a sure thing is that "FichaCliente" can have many "Reclamado" as it's needed. And that's fine, it works! Just to make it clear, the UF entity is the equivalent to me as what would be states in the US, thus, a given address belongs to a state (city, state...). As "Reclamados" are distinct entities, I can have one or more "Reclamados" belonging to the same UF.

That's where it fails!

If I have the same UF for two or more different "Reclamados", a error shows, as if, it was saving twice the same UF, although they're actually different, each one belonging to a different "Reclamado". It's not saving that same UF twice. It saves one for each "Reclamado"

An example of error is:

"The instance of entity type 'UF' cannot be tracked because another instance with the key value '{Id: 26}' is already being tracked. When attaching existing entities, ensure that only one entity instance with a given key value is attached."

How can I handle this?

Answer 1

尽管如果您将持久性模型与实际业务代码分离可以避免这种情况，但要解决这个问题，您必须在 SaveChangesAsync 之前遍历所有 UF 并针对每个 UF 执行以下操作

context.Entry(uf).State = EntityState.Unchanged;

Answer 2

Your entry is already tracked by the context. Just remove line context.FichasClientes.Update(ficha); and your code will work.

Update method is only useful when the entry is not tracking by the Context. Read more about update