c# - 多个标签云相关帖子的实体框架查询

Question

如果我有像这样的模型类

[Table("MTag")]
public class Tag
{
    [Key]
    [DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
    public int TagId { get; set; }
    public string TagLabel { get; set; }
    public virtual ICollection<TagRef> RefTags { get; set; }
}

[Table("TagRef")]
public class TagRef
{
    [Key]
    [DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
    public int TagRefId { get; set; }
    public virtual Tag Tag { get; set; }
    public virtual ICollection<Post> Posts { get; set; }
}

[Table("Post")]
public class Post
{
    [Key]
    [DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
    public int PostId { get; set; }
    public UserProfile User { get; set; }
    public string Title { get; set; }
    public string Description { get; set; }
    public string PostGuid { get; set; }
    public string Make { get; set; }
    public string Model { get; set; }
    public virtual ICollection<MTagRef> Tags { get; set; }
    public string ImageFileName { get; set; }
    public int Price { get; set; }
    public int ImageWidth { get; set; }
    public int ImageHeight { get; set; }

}

选择所有匹配帖子的可能查询是什么？您能否提示一下，如果我有 Car、Mobile 等标签，如何设置查询？

Answer 1

您有汽车、手机、车辆、电子产品和...等标签。

当您添加帖子时，您会添加一些标签。像这个网站（Stackoverflow）一样，当您添加问题时，您也会添加一些标签。现在您要选择所有带有特定标签的帖子。

以下方法返回具有一些标签的所有帖子：

public static IQueryable<Post> PostsWithTags(List<int> tagIds)
{
        Context c = new Context();
        var Query = (from Group in c.TagRefs.GroupBy(g => g.TagId) let GroupTags = Group.Select(g => g.TagId) where tagIds.All(gt => GroupTags.Contains(gt)) select Group.Select(g => g.Post).FirstOrDefault());

        return Query ;
}

Answer 2

简单提示：

var tags = db.Post.Where(m=>m.YourPropertyName == "YourPropertyValue").ToList();

这里

YourPropertyName = with which property you want to match.

YourPropertyValue = Value of your property.