Usually I\'m using this code
Member member = ctx.Members.Find(id);
member.Name = txtName.Text;
ctx.Entry(member).State = EntityState.Modified;
ctx.SaveChanges();
Like the other guys have mentioned your context tracks the changes to the object automatically.
I find it more useful for instance when I use return json to a mvc controller where the original object loses change tracking when first converted to json for the view. In that case I have to specifically set the objects entity state before saving changes.