如何使用IQueryable，Where 自定义函数

Question

var query = ctx.Order.AsQueryable();
            if (!string.IsNullOrEmpty(sale))
            {
                query = query.Where(o => o.sale == sale);
            }

 

if (!string.IsNullOrEmpty(key))
{
query = query.Where(o => myfunc(key));
}