Is it possible to configure to increment a property of an entity every time I call to SaveChages()?

[ComptonAlvaro]

Hello:

I have an entity in which I want to control concurrency. For that, in the database i have a version field but the entity doesn't need this property for doing its work, so I was thinking if there is some way to configure entity core to control concurrency.

I was thinking to use a shadow property, in this way:

public void Configure(EntityTypeBuilder<MyEntity> paramConfiguration)
{
    paramConfiguration.ToTable("MyTable");


    paramConfiguration.HasKey(o => o.Id);
    paramConfiguration.Property<long>(o => o.Id)
        .HasColumnName("ID")
        .HasColumnType("bigint")
        .IsRequired();

    paramConfiguration.Property<string>(o => o.Name)
        .HasColumnName("Name")
        .HasColumnType("varchar(200)")
        .IsRequired();

    paramConfiguration.Property<long>("Version")
        .HasColumnName("version")
        .HasColumnType("bigint")
        .IsRequired()
        .IsConcurrencyToken();
}

But I would like to know if there is some way to configure Entity Core to update version.

I have seen that HasValueGenerator generates a value when SaveChages() is called, but if I am not wrong, it works only when the entity is added to the context to be added, it doesn't work to update the value of a property of an existing entity.

So perhaps I was thinking something like this:

    public void Configure(EntityTypeBuilder<MyEntity> paramConfiguration)
    {
        paramConfiguration.ToTable("MyTable");


        paramConfiguration.HasKey(o => o.Id);
        paramConfiguration.Property<long>(o => o.Id)
            .HasColumnName("ID")
            .HasColumnType("bigint")
            .IsRequired();

        paramConfiguration.Property<string>(o => o.Name)
            .HasColumnName("Name")
            .HasColumnType("varchar(200)")
            .IsRequired();

        paramConfiguration.Property<long>("Version")
            .HasColumnName("version")
            .HasColumnType("bigint")
            .IsRequired()
            .IsConcurrencyToken(() => UpdateConcurrencyProperty());
    }


    private long UndateConcurrencyProperty()
    {
        return ((long)context.Entry(std).Property("Version").CurrentValue) + 1;
    }

In this way, I could handle concurrency in only once place, in the repository. Because if not, I would need to add a property to my domain entity and increase the value in the domain each time I modify the root entity or I handle some of its children. But I also I have to configure Entity Core to handle concurrency setting the version property. So I have this in two places.

If Entity Core would allow to increase the version property, I could avoid to have a version property in the domain, that it is not really its responsability, and I avoid too to have to configure the concurrency in two places, the domain and the repository.

It is true that in this case the version will be increased each time i call the SaveChages(), but in my case it is not a problem, because I have a repository only for commands, and I istantiate a repository each time I perform an action, so the entities that there is in the repository I will be needed to increase the version.

So in sumary, is it possible to configure the shadow property to be a concurrency token and increase its value each time I call the SaveChanges()?

Thanks.

[ajcvickers]

Covered in spirit by #2195