Question

我有这两个类：

public partial class Topic {
    public int TopicId { get; set; }
    public string Name { get; set; }
    public virtual ICollection<SubTopic> SubTopics { get; set; }
}

public partial class SubTopic {    
    public int SubTopicId { get; set; }
    public string Name { get; set; }
    public int TopicId { get; set; }
    public virtual Topic Topic { get; set; 
}

这是我目前的LINQ声明：

var subTopics = _subTopicsRepository
                .GetAll()
                .Where(s => s.TopicId == topicId)
                .ToList();

如何创建它以使subTopics变量也具有TopicId和Topic.Name，然后填充视图：

public partial class TopicSubTopic
{
    public int TopicId { get; set; }
    public int SubTopicId { get; set; }
    public string TopicName { get; set; }
    public string SubtopicName { get; set; }
}

Answer 1

这应该这样做

var subTopics = _subTopicsRepository
            .GetAll()
            .Where(s => s.TopicId == topicId && s.Topic.Name == "YourTopic")
            .Select new{TopicId  = s.Topic.TopicId,SubTopicId = s.TopicId,TopicName = s.Topic.Name,SubTopicName = S.Name};

然后在你的班级中添加一个构造函数

 public partial class TopicSubTopic {
    public TopicSubTopic(int topicID,int subTopicId,string topicName,string subTopicName)
    {
     TopicId = topicID;
     SubTopicid = subTopicID;
     TopicName = topicName;
     SubTopicName = subTopicName;
    }

    public int TopicId { get; set; }
    public int SubTopicId { get; set; }
    public string TopicName { get; set; }
    public string SubtopicName { get; set; } }

获取值和

 from item in subTopics.AsEnumerable()
          select new TopicSubTopic(item.Topicid,item.SubTopicid,item.TopicName,item.SubTopicName);

Answer 2

您应该可以通过虚拟财产访问主题。例如，

var subTopics = _subTopicsRepository
                .GetAll()
                .Where(s => s.TopicId == topicId && s.Topic.Name == "ExampleTopic")
                .ToList();

编辑：要填充ViewModel（包含模型的组合），我会使用类似AutoMapper的内容。这将允许您指定源模型中的哪些属性映射到视图模型上的某些属性。

在这种情况下，创建映射的语法示例如下所示：

        Mapper.CreateMap<SubTopic, TopicSubTopic>()
            .ForMember(dest => dest.TopicId, opt => opt.MapFrom(src => src.Topic.TopicId))
            .ForMember(dest => dest.SubTopicId, opt => opt.MapFrom(src => src.SubTopicId))
            .ForMember(dest => dest.TopicName, opt => opt.MapFrom(src => src.Topic.Name))
            .ForMember(dest => dest.SubTopicName, opt => opt.MapFrom(src => src.Name));

这允许视图在一个级别上拥有所需的一切，这就是我认为你想要的。

Answer 3

您需要连接这两个表，然后从两个表中选择一个列到一个匿名对象。

var topics = new System.Collections.Generic.List<Topic>();
var subTopics = new System.Collections.Generic.List<SubTopic>();
int topicId = 23984;
var details = from subtopic in subTopics
    where subtopic.TopicId == topicId
    join topic in topics on subtopic.TopicId equals topic.TopicId
    select new TopicSubTopic()
    {
        TopicId = topic.TopicId,
        SubTopicId = subtopic.SubTopicId,
        TopicName = topic.Name,
        SubtopicName = subtopic.Name
    };

http://msdn.microsoft.com/en-us/library/bb311040.aspx

如何在LINQ表达式中包含来自包含表的字段？

3 个答案: