emildr / insta_pr_decline_csharp.md

1. N+1 Queries **Always** query all data you need before executing anything. Incorrect: ```C# foreach (var id in itemIds) { await _context.Items.FirstOrDefaultAsync(x => x.Id == id); // Logic await _context.SaveChangesAsync(); } ``` Correct: ```C# var items = await _context.Items.Where(x => itemIds.Contains(x.Id)); foreach (var item in items) { // Logic } await _context.SaveChangesAsync(); ``` 2. 3+ Includes without AsSplitQuery() **Always** consider the query that will actually be executed. Incorrect ```C# await _context.Users .Include(u => u.Roles) .Include(u => u.Events) .Include(u => u.Installations) .ThenInclude(i => i.Meters) .ToListAsync(); ``` Correct: ```C# await _context.Users .Include(u => u.Roles) .Include(u => u.Events) .Include(u => u.Installations) .ThenInclude(i => i.Meters) .AsSplitQuery() .ToListAsync(); ``` 3. Todos without issues You **will** forget. ```C# var theThing = getTheThing(); // TODO: Do the right thing! ``` ```C# var theThing = getTheThing(); // TODO: Do the right thing! (#8383) ``` 4. Big queries without indexes If you are executing a query a lot. It must have an index.