Which method is better to get the number of an entity?-CodePudding

I need to get the number of products. I have two entities, the first SubCatgory and the second is Product. So I have two ways to get product count. the first:

var subcatgory = await _context.SubCategories.FirstOrDefaultAsync(m => m.Id == id);
int productCount = await _context.Products.CountAsync(p => p.SubCatgoryId == id);

the second:

var subcatgory = await _context.SubCategories.Include(s => s.Products).FirstOrDefaultAsync(m => m.Id == id);
int productCount = subcatgory.Products.Count();

Which one is better in terms of performance? Why? tip: I need subcatgory too.

Thank you for your answer

CodePudding user response：

Try the following query. It returns data in one roundtrip to database.

var result = await _context.SubCategories
    .Where(m => m.Id == id)
    .Select(sc => new 
     {
        Subcategory = sc,
        ProductCount = sc.Products.Count()
     })
    .FirstOrDefaultAsync();