c# - LINQ to SQL，我如何获得在字段中找到的搜索词的计数？

Question

有没有办法在 LINQ 中编写查询以返回在字段中找到的搜索词的计数

基本上，我希望它能工作:

var matches = from t in _db.Books
                          let score = GetScore(t, searchterms)
                          where score >= 1
                          orderby score descending
                          select t;

public static int GetScore(Book b, params string[] searchterms)
    {
        int count = 0;
        foreach (string term in searchterms)
        {
            if (b.Title.Contains(term))
                count++;
        }
        return count;
    }

但是，当然，这是行不通的。 我的小 GetScore 函数可以转换为 LINQ 吗？

谢谢。

编辑:我也希望乐谱可以访问。理想情况下，我会将我的结果选择到一个 SearchResults 类(对于 View )中，该类将包含一些图书信息和来自查询的图书分数。要更新我的查询，它会是这样的:

var matches = from t in _db.Books
                          let score = GetScore(t, searchterms)
                          where score >= 1
                          orderby score descending
                          select new SearchResult
                                                {
                                                    Title = t.Title,
                                                    Type = "Book",
                                                    Link = "Books/Details/" + t.BookID,
                                                    Score = score
                                                };

对不起，我最初没有更清楚。

Answer 1

如果不向数据库发出多个查询(基本上是每个搜索词一个)，您就无法做您想做的事。如果您乐于这样做，那么这里有一个简单的方法:

var terms = new [] { "s", "t", "r", "e", "b", "c", };

var ids =
    from term in terms
    from id in _db.Books
        .Where(book => book.Title.Contains(term))
        .Select(book => book.Id)
    group term by id into gts
    orderby gts.Count() descending
    select gts.Key;

var selectedIds = ids.Take(50).ToArray();

var query =
    from book in _db.Books
    where selectedIds.Contains(book.Id)
    select book;

我编写了 ids 以返回一个 id 列表，这些 id 按最先匹配的项排序。这是为了最接近地获得您在问题中想要的相同类型的结果。然后我决定使用 Take(50) 来获得前 50 个结果。您显然可以更改此策略以满足您的需要，但您必须以一组 ID 结束以在最终查询中使用。

希望对您有所帮助。

---

编辑:基于 OP 的编辑。

下面是查询包含分数的方法:

var terms = new [] { "s", "t", "r", "e", "b", "c", "l", "i", };

var idScores =
    from term in terms
    from id in _db.Books
        .Where(book => book.Title.Contains(term))
        .Select(book => book.BookID)
    group term by id into gts
    select new
    {
        Id = gts.Key,
        Score = gts.Count(),
    };

var selectedIds = idScores.Select(x => x.Id).Take(50).ToArray();

var selectedBooks =
    from book in _db.Books
    where selectedIds.Contains(book.BookID)
    select book;

var query =
    from b in selectedBooks.ToArray()
    join x in idScores on b.BookID equals x.Id
    orderby x.Score descending
    select new
    {
        Title = b.Title,
        Type = "Book",
        Link = "Books/Details/" + b.BookID,
        Score = x.Score,
    };