首先使用ef 5代码将继承的notmapped对象保存到基础对象

Question

I have a code first poco class called topic. From this I've created an inherited class called topicWith that contains some extra aggregated fields like the message count, and the last user that created a message within a topic. In my controller I fetch a topicWith first, then I would like to update the base topic with +1 on the number of times it's been read. If I try to save the topicWith object I get an error: The entity type TopicWith is not part of the model for the current context. I get this even though I've explicitly cast the object to "topic"

This is the short version of what I'm doing.

[NotMapped]
public class TopicWith : Topic
{
    public virtual int NumberOfMessages { get; set; }
}

var topics = from topic in context.Topics
                select
                    new TopicWith
                        {
                            ForumID = topic.ForumID,
                            TopicID = topic.TopicID,
                            Subject = topic.Subject,
                            Hide = topic.Hide,
                            Locked = topic.Locked,
                            Icon = topic.Icon,
                            NoOfViews = topic.NoOfViews,
                            Priority = topic.Priority,
                            Forum = topic.Forum,
                            Messages = topic.Messages,
                            NumberOfMessages = topic.Messages.Count()
                        };
var topicWith = topics.FirstOrDefault();
topicWith.NoOfViews++;
context.Topics.Add((Topic) topicWith);

What is the best way to solve this problem?

Answer 1

Possible solution

var topics = from topic in context.Topics
            select
                new {
                        Topic = topic,
                        NumberOfMessages = topic.Messages.Count()
                    };
var topicWith = topics.FirstOrDefault();
topicWith.Topic.NoOfViews++;
context.Topics.Add(topicWith.Topic);