C# 1对多关系中2个类之间的Linq表达式

我有两门课：

 public class Op
{
    [Key]
    public int OpId { get; set; }
    private OpportunitiesDb db = new OpportunitiesDb();

    [Required(ErrorMessage = "Opportunity title is required")]
    [DisplayName("Opportunity Title")]
    public string Title { get; set; }

    [DisplayName("Tags")]
    public ICollection<Tags> Tags { get; set; }
 }


 public class Tags
{
    [Key]
    public int Id { get; set; }
    public int OpId { get; set; }
    public string Tag { get; set; }

}

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分组依据

Tag

from r in db.Tags
join o in db.Ops on r.OpId equals o.OpId
group o by r.Tag into ops
select ops

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按标记筛选以获取您正在查找的Ops

我需要的是此搜索，这将在字符串查询变量中显示所有具有相同标记的Ops：

var AllOpsWithTagQuery = from r in db.Tags
           where(r.Tag.StartsWith(Query))
           join o in db.Opportunities on r.OpId equals o.OpId
           select o;

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这对我不起作用。它应该带来所有具有给定“标签”的操作

var AllOpsWithTagQuery = from r in db.Tags
           where(r.Tag.StartsWith(Query))
           join o in db.Opportunities on r.OpId equals o.OpId
           select o;