动态LINQ：将嵌套数据与父属性进行比较

Question

我有一个具有以下结构的课程：

 public class BestWayContext
{
    public Preference Preference { get; set; }
    public DateTime DueDate { get; set; }
    public List<ServiceRate> ServiceRate { get; set; }
}

public class ServiceRate
{
    public int Id { get; set; }
    public string Carrier { get; set; }
    public string Service { get; set; }
    public decimal Rate { get; set; }
    public DateTime DeliveryDate { get; set; }
}

我有动态linq表达式字符串

“偏好！= null＆amp;＆amp; ServiceRate.Any（Carrier == Preference.Carrier）”

我想在Dynamic LINQ中转换上面的字符串，如下所示：

  var expression = System.Linq.Dynamic.DynamicExpression.ParseLambda<BestWayContext, bool>(condition, null).Compile();

但它显示以下错误：

请纠正我，我做错了什么？

Answer 1

看起来你想做这样的事情：

var bwc = new BestWayContext
{
    Preference = new Preference { Carrier = "test" },
    DueDate = DateTime.Now,
    ServiceRate = new List<ServiceRate>
    {
        new ServiceRate
        {
            Carrier = "test",
            DeliveryDate = DateTime.Now,
            Id = 2,
            Rate = 100,
            Service = "testService"
        }
    }
};

string condition = "Preference != null && ServiceRate.Any(Carrier == @0)";
var expression = System.Linq.Dynamic.DynamicExpression.ParseLambda<BestWayContext, bool>(condition, bwc.Preference.Carrier).Compile();
bool res = expression(bwc); // true
bwc.ServiceRate.First().Carrier = "test1"; // just for testing this -> there is only one so I've used first
res = expression(bwc); // false

Answer 2

您想使用属于BestWayContext的Preference，但您没有告诉编译器。如果我在Linq上写下你的表达，我将按如下方式进行：

[BestWayContext列表]。其中（f =＆gt; f.Preference！= null＆amp;＆amp; f.ServiceRate.Where（g =＆gt; g.Carrier == f.Preference.Carrier） ）;

如您所见，我指定使用BestWayContext的首选项。