問題描述

我似乎遇到了這個問題.我有一個帶有 ID 的任務表和一個標簽表，它有一個標簽字段和一個到任務表的外鍵約束.

I seem to be having trouble with this. I have a Task table with an ID, and a Tag table, that has a tag field and a foreign key constraint to the task table.

我希望能夠通過標簽對任務執行 AND 搜索.例如，如果我搜索帶有可移植性"和測試"標簽的任務，我不想要帶有可移植性"而不是測試"標簽的任務.

I want to be able to perform AND searches for tasks by tags. So for example, if I search for tasks with the tags "portability" and "testing", I don't want tasks that are tagged with "portability" and not "testing".

我嘗試了以下語法:

 var tasks = (from t in _context.KnowledgeBaseTasks
                     where t.KnowledgeBaseTaskTags.Any(x => tags.Contains(x.tag))
                     select KnowledgeBaseTaskViewModel.ConvertFromEntity(t)
                    ).ToList();

這當然是 OR 搜索，而不是 AND 搜索.我不知道如何將其實際切換為 AND 搜索.

This of course does an OR search, not an AND search. I can't figure out how to actually switch this to be an AND search.

編輯我還需要能夠搜索任務包含的 X 個標簽中的 2 個.因此，如果任務被標記為錯誤修復"、可移植性"、測試"并且我搜索測試"和可移植性"，該任務仍會顯示.

Edit I also need to be able to search for 2 out of X tags that a task contains. So if the task is tagged with "bugfix", "portability", "testing" and I search for "testing" and "portability", that task will still show up.

推薦答案

你想做的這個

LinqToSql 可能看起來像:

the LinqToSql might look like:

List<int> myTags = GetTagIds();
int tagCount = myTags.Count;

IQueryable<int> subquery =
  from tag in myDC.Tags
  where myTags.Contains(tag.TagId)
  group tag.TagId by tag.ContentId into g
  where g.Distinct().Count() == tagCount
  select g.Key;

IQueryable<Content> query = myDC.Contents
  .Where(c => subQuery.Contains(c.ContentId));

我還沒有測試過這個，Distinct 位可能有點差.檢查生成的 sql 以確保.

I haven't tested this and the Distinct bit might be off a little. Check the generated sql to be sure.

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