c# - Linq 搜索对象列表

Question

我有这门课:

public class ExamReviewRequested
{
    public List<ExamReviewRequest> Reviews { get; set;}
}

它的 reviews 属性有一个这个类的列表:

public class ExamReviewRequest
{
    public string EventCode { get; set; }
    public bool Requested { get; set; }
}

如何使用 LINQ 搜索特定的 EventCode 并返回带有该 EventCode 的选定 ExamReviewRequest？在我看来，这两个(Row.EventCode 具有我想要搜索的值):

ExamReviewRequest er = ViewBag.ExamReviews.Single(x => x.EventCode == Row.EventCode)

ExamReviewRequest er = ViewBag.ExamReviews.Reviews.FirstOrDefault(x => x.EventCode == Row.EventCode)

返回这个错误:

Cannot use a lambda expression as an argument to a dynamically dispatched operation without first casting it to a delegate or expression tree type

我看过几篇关于这个主题的帖子，但无法使其中任何一篇发挥作用。

Answer 1

当您分配 ExamReviews 时到 ViewBag他们变成了dynamic没有类型设置的对象。错误消息告诉您需要先转换它才能使用 Linq。

你能做什么

我看不到你在哪里分配 ViewBag.ExamReviews所以如果它的类型是 IEnumerable<ExamReviewRequest>然后:

var examReviews = (IEnumerable<ExamReviewRequest>)ViewBag.ExamReviews
var examReviewRequest = examReviews.Single(x => x.EventCode == Row.EventCode)

或者如果它是 ExamReviewRequested 类型然后:

var examReviews = (ExamReviewRequested)ViewBag.ExamReviews
var examReviewRequest = examReviews.Requests.Single(x => x.EventCode == Row.EventCode)

你应该做什么

你不应该分配 List<ExamViewRequest>/ExamReviewRequested到 ViewBag .这样你可以这样做:

// Code to set model previous
var examReviewRequested = model.ExamReviews.Single(x => x.EventCode == Row.EventCode);

在哪里model类型为 ExamReviewRequested