UnnecessaryJoinsBenchmark.cs

[MemoryDiagnoser]
public class UnnecessaryJoinsBenchmark : Benchmark
{
    [Benchmark]
    public async Task<List<CustomView>> WithJoins()
    {

        var books = await (from authors in Context.Authors
            where authors.Id > 5
            join book in Context.Books on authors.Id equals book.AuthorId select book)
            .Select(x => new CustomView
        {
            Title = x.Title,
            AuthorFirstName = x.Author.FirstName
        }).ToListAsync();

        return books;
    }

    [Benchmark]
    public async Task<List<CustomView>> WithoutJoins()
    {
        var authors = await (from author in Context.Authors where author.Id > 5 select author).Select(x => x).ToListAsync();
        var books = await (from book in Context.Books where authors.Contains(book.Author) select book)
            .Select(x => new CustomView
        {
            Title = x.Title,
            AuthorFirstName = x.Author.FirstName
        }).ToListAsync();

        return books;
    }

    public class CustomView
    {
        public string Title { get; set; }
        public string AuthorFirstName { get; set; }
    }
}