Question

我有一个关于我在LINQ写的查询的查询，我希望有人可以提供帮助。基本上我有以下（示例数据）

ProductCode  LanguageID   LegislationId   Version
1234         English       UK              1
1234         English       UK              2
5678         English       UK              1
9999         English       UK              1
9999         English       UK              2
9999         Spanish       Spain           1

所以，我需要做的是根据用户提供的标准返回记录，包括LanguageID和Description。这里棘手的部分是，如果有相同产品代码，语言和法规的多个版本，那么我只想返回最新版本。

所以...我现在的代码如下（pLegislations包含一个以逗号分隔的立法清单）：

List<string> legList = pLegislations.Split(',').ToList();
IEnumerable<MyClass> results = null;

results = (from a in context.ALLProducts
           let prodCode = a.ProductCode
           let prodDesc = a.ProductDescription
           where legList.Contains(a.LegislationID) &&
                 (a.LanguageID == pLanguage || pLanguage == null) &&
                  a.BrandName == pMarket &&
                 (prodCode.Contains(pSearch) || prodDesc.Contains(pSearch) || 
                                                pSearch == string.Empty) &&
                 prodCode[0] != 'x' &&
                ((pMarket == "testMarket") ? prodCode.StartsWith("0") : true)
                select new MyClass
                {
                   BrandName = a.BrandName,
                   BulkCode = prodCode,
                   BulkDescription = prodDesc,
                   Language = a.LanguageName,
                   LanguageCode = a.LanguageID
                }).ToList();

现在一切正常，没有多个版本，所以我的问题是 - 如何过滤它，以便只有当ProductCode，Language和Legislation匹配时返回最新版本，即如果我要通过语言=＆＃39;英语＆＃39;和立法=＆＃39;英国＆＃39;那么我期待以下结果：

ProductCode  LanguageID   LegislationId   Version
1234         English       UK              2
5678         English       UK              1
9999         English       UK              2
9999         Spanish       Spain           1

提前致谢

安德鲁

Answer 1

按ProductCode（1）对结果进行分组，并从每个具有最大Version值（2）的组项中进行选择：

results = (from a in context.ALLProducts
           let prodCode = a.ProductCode
           let prodDesc = a.ProductDescription
           where legList.Contains(a.LegislationID) &&
                 (a.LanguageID == pLanguage || pLanguage == null) &&
                  a.BrandName == pMarket &&
                 (prodCode.Contains(pSearch) || 
                  prodDesc.Contains(pSearch) || 
                  pSearch == string.Empty) &&
                  prodCode[0] != 'x' &&
                 ((pMarket == "testMarket") ? prodCode.StartsWith("0") : true)
           group a by a.ProductCode into g // 1
           let lastProduct = g.OrderByDescending(x => x.Version).First() // 2
           select new MyClass
                {
                   BrandName = lastProduct.BrandName,
                   BulkCode = prodCode,
                   BulkDescription = prodDesc,
                   Language = lastProduct.LanguageName,
                   LanguageCode = lastProduct.LanguageID
                }).ToList();

LINQ to SQL - 跨多个列的不同记录

1 个答案: