LINQ多关键字搜索到PagedList

Question

我在这里有点迷路，我尝试了几种不同的方法来解决它。到目前为止，我很难写出 LINQ 来做我想做的事。

我想获取用户输入的字符串，它可以是多个关键字，可以用空格或“，”分隔。

这里的作品抓取整个搜索词并将其与 Post 中的标题或我可能拥有的任何标签进行比较。我希望用户输入 "HTML Preview"，这将匹配一个名为 post 的 "Preview the World" 和标签 "HTML"、"CSS" 等....

此查询将不起作用...但我正在尝试对其进行修改以使其起作用。

public IPagedList<Post> SearchResultList(string searchTerm, int resultsPerPage, int page)
{
    string[] terms = searchTerm.Split(null);

    TNDbContext context = DataContext;
    return context.Posts
        .Include(a => a.Tags)
        .Include(b => b.Comments)
        .Where(c => (c.Title.Contains(searchTerm) || c.Tags.Any(d => d.Name.StartsWith(searchTerm))) || searchTerm == null)
        .OrderByDescending(x => x.Views)
        .ToPagedList(page, resultsPerPage);

}

我试着写这个而不是其他 "Where" 语句

.Where(x => (terms.All(y => x.Title.Contains(y))) || terms == null)

但它一直抛出这个错误

Cannot compare elements of type 'System.String[]'. Only primitive types, enumeration types and entity types are supported.

供参考：

public class Post
{
    public Post()
    {
        Tags = new HashSet<Tag>();
        Comments = new HashSet<Comment>();
    }

    public int Id { get; set; }
    public string Title { get; set; }
    public string UrlTitle { get; set; }
    public DateTime Date { get; set; }

    public DateTime DateEdited { get; set; }

    public string Body { get; set; }

    public string Preview { get; set; }

    public string PhotoPath { get; set; }

    public int Views { get; set; }



    //Navigational

    public ICollection<Tag> Tags { get; set; }

    public ICollection<Comment> Comments { get; set; }

}

public class Tag
{
    public Tag()
    {
        Post = new HashSet<Post>();
    }


    public int Id { get; set; }
    public string Name { get; set; }

    public int TimesTagWasUsed { get; set; }


    //Navigational

    public ICollection<Post> Post { get; set; }


}

Answer 1

您需要从基本查询开始，然后为每个搜索词不断添加 where 子句。试试这个：

TNDbContext context = DataContext;

//Create the base query:
var query = context.Posts
        .Include(a => a.Tags)
        .Include(b => b.Comments)
        .OrderByDescending(x => x.Views);

//Refine this query by adding "where" filters for each search term:
if(!string.IsNullOrWhitespace(searchTerm))
{
    string[] terms = searchTerm.Split(" ,".ToCharArray(),
                                      StringSplitOptions.RemoveEmptyEntries);
    foreach(var x in terms)
    {
        string term = x;
        query = query.Where(post => (post.Title.Contains(term) ||
                                     post.Tags.Any(tag => tag.Name.StartsWith(term))));
    }
}

//Run the final query to get some results:
var result = query.ToPagedList(page, resultsPerPage);

return result;

Answer 2

您可以使用额外的 'from' 语句嵌套查询，所以这样的事情应该有效：

var list = (from post in context.Posts.Include(a => a.Tags).Include(b => b.Comments)
            from term in terms
            where post.Title.Contains(term) || post.Tags.Any(d => d.Name.StartsWith(term))
            select post).OrderByDescending(x => x.Views);

LINQ多关键字搜索到PagedList

LINQ multiple keyword search to PagedList

c#

linq

asp.net-mvc

pagedlist