Entity Framework - What is the advantage of automatic change detection?

When working with the EntityObject derived types or change-tracking proxy objects, the Entity Framework automatically tracks changes made to entities as they occur

What advantage does this give me? Without this my changes are still detected when I call开发者_JS百科 SaveChanges and my POCO is persisted correctly.

Also, why do a lot of the online tutorials for EF explicitly change the state to modified after they make a change, what purpose does this serve?

context.Entry(model).State = EntityState.Modified;

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EF tracks changes of your entities, so that when you call SaveChanges() it will know which entities to update in database, i.e. - what SQL to generate and run against db.

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The reason for having below line, is to attach a model which is currently not being tracked and set its state to modified.

context.Entry(model).State = EntityState.Modified;

You need to do it in case if you created an instance of your Entity yourself, e.g. -

var customer = new Customer();

This will not add your customer to the DbContext and therefore its not being tracked. So you need to use context.Entry(customer) for that.