Microsoft.EntityFrameworkCore DbSet.Update([NotNullAttribute] TEntity entity) use case

Question

I am relatively new to EntityFrameworkCore. I saw some code that used the Update function and that caught my attention. The question is basically "Why use it?"

What would be the difference between:

var m = await context.MyModel.Where(e => e.Id == model.Id).FirstOrDefaultAsync();
if (m != null)
{
    m.Foo = model.Foo;
    m.Bar = model.Bar;
    context.MyModel.Update(m);
    await context.SaveChangesAsync();
}

and

var m = await context.MyModel.Where(e => e.Id == model.Id).FirstOrDefaultAsync();
if (m != null)
{
    m.Foo = model.Foo;
    m.Bar = model.Bar;
    await context.SaveChangesAsync();
}

From what I've already read the Update will mark all properties within MyModel as modified, but what would the difference in result be between those two? As far as I know the modified fields will be saved regardless of "Update" when I call "SaveChanges", is the difference that if I don't "Update" the only two properties that will be modified are Foo and Bar, and in case of "Update" ALL of them will be modified? I did not find any explanation to why using "Update" would be preferable or vice versa.

Thanks.

Answer 1

Assuming context does not have change tracking disabled, nothing. If the entity to be updated is not being tracked by the context (eg context.ChangeTracker.QueryTrackingBehavior = QueryTrackingBehavior.NoTracking; or you use context.MyModel.AsNoTracking()... for your query), then calling DbSet<T>.Update will track the entity with an EntityState of Modified . In such a case, your second example won't save any changes to the store.