What is the proper names for the following mutating methods?

static void Mutator_A(ref File file)
{
    file = new File { Id = Random.Shared.Next(), Name = Path.GetRandomFileName() };
}
static void Mutator_B(File file)
{
    file.Id = Random.Shared.Next();
    file.Name = Path.GetRandomFileName();
}
class File
{
    public int Id;
    public string Name = null!;
}