Question

我有下面的SQL查询，我试图转换为Linq但不能让它完全工作。

  select l.nid,
         l.sName,
         l.language,
         coalesce(p.kLanguage, 0) kLanguage

   from vLanguage l
        left join
             (
                select pl.kLanguage, 
                       p.nid,
                       p.sName

                from vProductLanguage pl
                    left join vProduct p 
                           on pl.kProduct = p.nid
                where p.nid = 1
             ) p
  on l.nid = p.kLanguage
  where l.bClosed =0

我已经在我的WCF服务

中管理了这个

    [WebInvoke(Method = "PUT", RequestFormat = WebMessageFormat.Json, ResponseFormat = WebMessageFormat.Json, UriTemplate = "ProductLanguageList")]
    public List<LookUpProductLanguage> GetProductLanguageList()
    {
        var passedProductId = int.Parse("12");
        var query = from languageEntity in _languageEntityRepository.AsQueryable()
                    join subQueryResult in (from productLanguageEntity in _productLanguageEntityRepository.AsQueryable() join productEntity in _productRepository.AsQueryable() on productLanguageEntity.LanguageProductId equals productEntity.Id into joinedProductLanguage
                                            from productLanguageJoin in joinedProductLanguage.DefaultIfEmpty() where productLanguageJoin.Id.Equals(passedProductId)
                                            select new {LanguageId = productLanguageEntity.LanguageId}
                                           ) on languageEntity.Id equals  subQueryResult.LanguageId

        return null;
    }

目前我已经返回null但是想要返回sql查询中提到的列。我在行连接subQueryResult附近得到错误“无法从查询中推断出类型参数”。我在这是要干嘛？请纠正我，因为我确信我做错了。

Answer 1

最后管理。这是我的查询。

 [WebInvoke(Method = "PUT", RequestFormat = WebMessageFormat.Json, ResponseFormat = WebMessageFormat.Json, UriTemplate = "ProductLanguageList")]
    public List<LookUpProductLanguage> GetProductLanguageList(GetParameters param)
    {
        var passedProductId = int.Parse(param.ProductId);
        var query = from languageEntity in _languageEntityRepository.AsQueryable()
                    join subQueryResult in
                        (from productLanguageEntity in _productLanguageEntityRepository.AsQueryable()
                         join productEntity in _productRepository.AsQueryable() on
                             productLanguageEntity.LanguageProductId equals productEntity.Id into
                             joinedProductLanguage
                         from productLanguageJoin in joinedProductLanguage.DefaultIfEmpty()
                         where productLanguageJoin.Id.Equals(passedProductId)
                         select new {productLanguageEntity.LanguageId}
                        ) on languageEntity.Id equals subQueryResult.LanguageId into a
                    from b in a.DefaultIfEmpty()
                    where languageEntity.Closed == 0 

                    select new LookUpProductLanguage {LanguageId = languageEntity.Id, LanguageName = languageEntity.Name,LanguageCode = languageEntity.Language,LanguageProductId = b.LanguageId  };

        return query.ToList();

    }

非常感谢那些努力回答我的人。

无法获得工作linq子查询

1 个答案: