How can I log all entities change, during .SaveChanges() using EF code first?

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You can get the before and after values for all changed entities by going through DbContext.ChangeTracker. Unfortunately the API is a little verbose:

var changeInfo = context.ChangeTracker.Entries()
            .Where (t => t.State == EntityState.Modified)
            .Select (t => new {
                Original = t.OriginalValues.PropertyNames.ToDictionary (pn => pn, pn => t.OriginalValues[pn]),
                Current = t.CurrentValues.PropertyNames.ToDictionary (pn => pn, pn => t.CurrentValues[pn]),
            });

You can modify that to include things like the type of the entity if you need that for your logging. There is also a ToObject() method on the DbPropertyValues (the type of OriginalValues and CurrentValues) you could call if you already have a way to log whole objects, although the objects returned from that method will not have their navigation properties populated.

You can also modify that code to get all entities in the context by taking out the Where clause, if that makes more sense given your requirements.

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