我有以下型号：

public class User
    {
       public long Id { get; set; }
       public string? Name { get; set; }
       public string? Surname { get; set; }
       public string? PhoneNumber { get; set; }
       public IEnumerable<Sale>? Sales { get; set; }
    }

    public class Product
    {
       [Key]
       public int Id { get; set; }
       public string Name { get; set; }
       public decimal Price { get; set; }
       public IEnumerable<Sale>? Sales { get; set; }
    }
    
    public class Sale
    {
       public int Id { get; set; }
       public User? User { get; set; }
       public List<SaleItem> SaleItems { get; set; }
       public DateTime CreatedDt { get; set; }
    }

    public class SaleItem
    {
        public int Id { get; set; }
        public Sale? Sale { get; set; }
        public Product? Product { get; set; }
        public int Count { get; set; }
    }

需要获得按客户和产品分组的计数和价格。
我试图用下面的方法解决这个问题：

var list = await context.SaleItems
    .Include(x => x.Product)
    .Include(x => x.Sale).ThenInclude(x => x.User)
    .Select(x => new
    {
        UserId = x.Sale.User.Id,
        UserName = x.Sale.User.Name,
        ProductId = x.Product.Id,
        ProductName = x.Product.Name,
        TotalCount = x.Count,
        TotalPrice = x.Product.Price * x.Count
    })
    .GroupBy(x => new { x.UserId, x.ProductId })
    .SelectMany(x => x)
    .ToListAsync();

但它不工作。谢谢！