Context trying to delete the same record twice

Question

I’m having a problem, actually it must be the same lack of knowledge, at the time of deleting a record using Entity Framework 6.

When I try to delete a record that cannot be deleted because it has references, it gives the following error:

So far, so good.

Ai I will try to delete another record, which I am sure has no reference, and it gives the same error, in fact is trying to delete again the previous record.

If I exit the screen and enter again then I can delete the record normally as long as I don’t try to delete another one before it generates the error.

Does anyone have a light? VLW

EDIT: Follow my code to better understand:

Screen signature:

private readonly ICategoriaAppService _categoriaApp;
private CategoriaViewModel _categoria;

public FormCategorias(ICategoriaAppService categoriaAppService)
{
    _categoriaApp = categoriaAppService;
    InitializeComponent();
}

Method to exclude:

private void btnExcluir_Click(object sender, EventArgs e)
{
    DialogResult resposta = MessageBox.Show("Deseja excluir este registro?", "Excluir", MessageBoxButtons.YesNo, MessageBoxIcon.Question);
    switch (resposta)
    {
        case DialogResult.Yes:
            var categoriaDomain = _categoriaApp.ObtemPeloID(_categoria.Numero_Categoria);
            _categoriaApp.Excluir(categoriaDomain);
            MessageBox.Show("Registro excluido com sucesso");
            break;
        case DialogResult.No:
            break;
    }
}

Appservice:

private readonly ICategoriaService _categoriaService;

public CategoriaAppService(ICategoriaService categoriaService) : base(categoriaService)
{
    _categoriaService = categoriaService;
}

public void Excluir(TEntity obj)
{
    _serviceBase.Remove(obj);
}

Service:

public class ServiceBase<TEntity> : IDisposable, IServiceBase<TEntity> where TEntity : class
{
    protected ControleEstoqueContexto Db = new ControleEstoqueContexto();

    public ServiceBase()
    {
        Db.Configuration.AutoDetectChangesEnabled = false;
    }

    public virtual void Remove(TEntity obj)
    {
        try
        {
            Db.Set<TEntity>().Remove(obj);
            Db.SaveChanges();
        }
        catch (Exception e)
        {
            Db.Dispose();
            Db = new ControleEstoqueContexto();
            throw e;
        }
    }

    //ETC
}

EDIT 2: Solved by putting Try catch and redoing Db.Context. Above changed code.

Answer 1

Putting your code makes it easier to point out the problem.

What seems to be happening to you is this.

Contexto.Objetos.Remove(instancia1);
Contexto.SaveChanges();

Error... After the mistake you make:

Contexto.Objetos.Remove(instancia2);
Contexto.SaveChanges();

Whereas instancia2 has no key. Only the context still has the "order" to exclude the instancia1. And he tries to delete both instances. So he makes a mistake in trying to delete 1. Got it? After the error redoes the context, or sees the best logic for you (not in your code it is difficult to say what it would be) and tests.

When you close the screen and open again the context is redone, so when you redo only the Remove(instancia2) it works.

UPDATING

You in the form load inject an instance of the (very cool) context. During the execution of the events you will use the same context.

First thing I would do is treat the mistake, or make it delete the relationship or not even let it get there. That’s what I suggest.

If it’s not possible, the best thing to do is to create the new one, but don’t forget to make one Dispose() of the current.

Here has another response suggesting also the new instead of changing the status of the object that is to be deleted.

Answer 2

In its place, I would not inject into the form a service, but rather a context. A tutorial from Microsoft goes exactly in this line.

This is another problem of the highlighted context. You load the data using a context and try the persistence using another context.