使用从 EF 查询获取的扩展属性将 EF 查询结果转换为扩展类型

发布于 2024-12-12 08:31:52 字数 949 浏览 0 评论 0原文

我有一个 Tag 对象：

public class Tag
{
    public int TagID { get; set; }
    public string Name { get; set; }

    public virtual ICollection<Job> Jobs { get; set; }

    public Tag()
    {
        Jobs = new HashSet<Job>();
    }
}

和扩展：

public class RecentTag : Tag
{
    public int Count { get; set; }
}

...并且我正在尝试检索最近标签对象的列表，其中包含添加到每个对象的查询中的计数：

public IEnumerable<RecentTag> GetRecentTags(int numberofdays)
{
    var tags = Jobs
        .Where(j => j.DatePosted > DateTime.Now.AddDays(-(numberofdays)))
        .SelectMany(j => j.Tags)
        .GroupBy(t => t, (k, g) => new
        {
            RecentTag = k,
            Count = g.Count()
        })
        .OrderByDescending(g => g.Count);

    // return RecentTags { TagID, Name, Count, Jobs }
}

那么，如何将查询结果转换为最近标签类型和返回扩展对象的列表？

任何帮助将不胜感激。提前致谢！

原文

I've got a Tag object:

public class Tag
{
    public int TagID { get; set; }
    public string Name { get; set; }

    public virtual ICollection<Job> Jobs { get; set; }

    public Tag()
    {
        Jobs = new HashSet<Job>();
    }
}

and extended:

public class RecentTag : Tag
{
    public int Count { get; set; }
}

...and I'm trying to retrieve a list of RecentTag objects with Count from the query added to each object:

public IEnumerable<RecentTag> GetRecentTags(int numberofdays)
{
    var tags = Jobs
        .Where(j => j.DatePosted > DateTime.Now.AddDays(-(numberofdays)))
        .SelectMany(j => j.Tags)
        .GroupBy(t => t, (k, g) => new
        {
            RecentTag = k,
            Count = g.Count()
        })
        .OrderByDescending(g => g.Count);

    // return RecentTags { TagID, Name, Count, Jobs }
}

So, how do I cast results of the query to RecentTag type and return the list of extended objects?

Any help would be appreciated. Thanks in advance!

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东走西顾 2024-12-19 08:31:52

如果Jobs实际上是Tags的集合，并且它们实际上是RecentTag对象，那么您可以简单地使用Cast方法。

var rtags = tags.Cast<RecentTags>;

但是，如果 Jobs 不是标签的集合，那么您需要投影到最近标签对象中。

var rtags = tags.Select(x => new RecentTags() { // assign the members });

if Jobs is actually a collection of Tags, and they are in fact RecentTag objects, then you can simply use the Cast method.

var rtags = tags.Cast<RecentTags>;

However, if Jobs is not a collection of tags, then you need to project into a RecentTags objects..

var rtags = tags.Select(x => new RecentTags() { // assign the members });

回复收藏 0 原文

过期以后 2024-12-19 08:31:52

我最终做了：

public IEnumerable<RecentTag> GetRecentTags(int numberofdays)
{
    DateTime startdate = DateTime.Now.AddDays(-(numberofdays));

    IEnumerable<RecentTag> tags = Jobs
        .Where(j => j.DatePosted > startdate) // Can't use DateTime.Now.AddDays in Entity query apparently
        .SelectMany(j => j.Tags)
        .GroupBy(t => t, (k, g) => new RecentTag
        {
            TagID = k.TagID,
            Name = k.Name,
            Count = g.Count()
        })
        .OrderByDescending(g => g.Count)
        .Select(a => a);

    return tags;
}

I ended up doing:

public IEnumerable<RecentTag> GetRecentTags(int numberofdays)
{
    DateTime startdate = DateTime.Now.AddDays(-(numberofdays));

    IEnumerable<RecentTag> tags = Jobs
        .Where(j => j.DatePosted > startdate) // Can't use DateTime.Now.AddDays in Entity query apparently
        .SelectMany(j => j.Tags)
        .GroupBy(t => t, (k, g) => new RecentTag
        {
            TagID = k.TagID,
            Name = k.Name,
            Count = g.Count()
        })
        .OrderByDescending(g => g.Count)
        .Select(a => a);

    return tags;
}

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