这很好用。但是我如何自定义添加过滤器的条件呢？input是用户输入的值

var resultList = dbContext.BuyerBill
                 .Include(x=>x.BuyerBillItems.Where(x=>x.Status == input.Status && x.BuildTime > input.BeginTime && x.BuildTime < input.EndTime))
                 .ToList();

我想要的方式：

var query = WhereIf(input.Status!=null,x=>x.Status == input.Status);
query = WhereIf(input.BeginTime!=null,x=>x.BuildTime > input.BeginTime);
query = WhereIf(input.EndTime!=null,x=>x.BuildTime > input.EndTime);

这是我的实体

public class BuyerBill
{
    public BuyerBill()
    {
        BuyerBillItems = new List<BuyerBillItems>();
    }
    public int Id {get;set;}
    public int BuyUserId {get;set;}
    public int OrderId {get;set;}
    public List<BuyerBillItems> BuyerBillItems { get; set; }
    ....
}

public class BuyerBillItems
{
    public int Id {get;set;}
    public int BuyerBillId {get;set;}
    public decimal Fee {get;set;}
    public int Status {get;set;}
    public dateTime CreateTime {get;set;}
    public BuyerBill BuyerBill {get;set;}
    ....
}

1、如果用户没有选择时间查询

Select * from BuyerBill as buy inner join BuyerBillItems As item On buy.Id=item.BuyerBillId 
                          where item.Status=1

2、如果用户选择时间查询

Select * from BuyerBill as buy inner join BuyerBillItems as item on buy.Id=item.BuyerBillId 
                            where item.Status=1 and item.BuildTime > '2022-7-19' and item.BuildTime < '2022-7-19'

如何使用efcore实现我描述的SQL条件？
主要是想根据条件过滤子实体，如果只有一个实体，我知道可以用Where（）方法过滤，但是不知道子实体怎么用条件过滤
我用LinqKit解决了上面的问题，但现在我有了一个新的问题。

var predicatess = PredicateBuilder.New<BuyerBillItems>(true);
            predicatess = predicatess.And(x => x.CreateTime > StringHelper.AddDateTime("2022-07-16"));
            predicatess = predicatess.And(x => x.Status == 2);
            //I'm dumb and this line of code seems redundant. But I don't know how to convert implicitly
            var convertPredicate = (Expression<Func<BuyerBillItems, bool>>)predicatess;

            var query = dbContext.BuyerBill.AsExpandable().Include(x => x.BuyerBillItems.Where(x => convertPredicate.Invoke(x)))
                .Where(x => x.BuyerBillItems.Any(s => convertPredicate.Invoke(s)))
                .Where(x => x.BuyUserId == 4);

            //If you don't use Select, everything is normal
            var result1 = query.ToList();

            //BuyerBillItemsDto result is incorrect after using Select
            var result2 = query.Select(x => new BuyerBillDto
            {
                Id = x.Id,
                BuyUserId = x.BuyUserId,
                OrderId = x.OrderId,
                BuyerBillItemsDto = mapper.Map<List<BuyerBillItems>, List<BuyerBillItemsDto>>(x.BuyerBillItems)
            }).ToList();

我必须使用select筛选列以避免性能损失