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Question

这是我的 JSON 字符串的样子：

{
    "?xml" : {
        "@version" : "1.0",
        "@encoding" : "UTF-8"
    },
    "DataFeed" : {
        "@FeedName" : "content",
        "now" : "2016-10-17T14:11:38.00",
        "Content" : [{
                "ContentData" : {
                    "@statusType" : "Published",
                    "@isReleased" : "Yes",
                    "@docId" : "21756",
                    "ProductStatus" : {
                        "@productCategory" : "Issuer",
                        "@focus" : "Issuer",
                        "Symbol" : {
                            "@PrimarySymbol" : "GOOGL",
                            "@SecondarySymbol" : "Google",
                            "@BmId" : "1790"
                        }
                    },
                    "ContentVersion" : {
                        "@versionId" : "1",
                        "@lastVersion" : "true",
                        "@lastPublished" : "true",
                        "Url" : [{
                                "@type" : "XML",
                                "@size" : "146410",
                                "#cdata-section" : "https://aaa.yyy.com/docs/xml/708893eb-1fd9-4278-8b0e-e7e0738d8105.xml"
                            }, {
                                "@type" : "HTML",
                                "@size" : "46105",
                                "#cdata-section" : "https://aaa.yyy.com/docs/html/708893eb-1fd9-4278-8b0e-e7e0738d8105.html"
                            }, {
                                "@type" : "PDF",
                                "@size" : "1274885",
                                "#cdata-section" : "https://aaa.yyy.com/docs/pdf/708893eb-1fd9-4278-8b0e-e7e0738d8105.pdf"
                            }, {
                                "@type" : "ALTERNATE PDF",
                                "@size" : "60960",
                                "#cdata-section" : "https://aaa.yyy.com/docs/shortPdf/708893eb-1fd9-4278-8b0e-e7e0738d8105.pdf"
                            }
                        ]
                    }
                }
            }, {
                "ContentData" : {
                    "@statusType" : "Published",
                    "@isReleased" : "Yes",
                    "@docId" : "22457",
                    "ProductStatus" : {
                        "@productCategory" : "Issuer",
                        "@focus" : "Issuer",
                        "Symbol" : {
                            "@PrimarySymbol" : "AAPL",
                            "@SecondarySymbol" : "Apple",
                            "@BmId" : "1121"
                        }
                    },
                    "ContentVersion" : [{
                            "@versionId" : "1",
                            "@lastVersion" : "false",
                            "@lastPublished" : "false",
                            "Url" : [{
                                    "@type" : "XML",
                                    "#cdata-section" : "https://aaa.yyy.com/docs/version/708893eb-1fd9-4278-8b0e-e7e0738d8105.1476742297.xml"
                                }, {
                                    "@type" : "HTML",
                                    "#cdata-section" : "https://aaa.yyy.com/docs/version/708893eb-1fd9-4278-8b0e-e7e0738d8105.1476742297.html"
                                }, {
                                    "@type" : "PDF",
                                    "#cdata-section" : "https://aaa.yyy.com/docs/version/708893eb-1fd9-4278-8b0e-e7e0738d8105.1476742297.pdf"
                                }, {
                                    "@type" : "ALTERNATE PDF",
                                    "#cdata-section" : "https://aaa.yyy.com/docs/version/708893eb-1fd9-4278-8b0e-e7e0738d8105.1476742297_short.pdf"
                                }
                            ]
                        }, {
                            "@versionId" : "2",
                            "@lastVersion" : "true",
                            "@lastPublished" : "true",
                            "Url" : [{
                                    "@type" : "XML",
                                    "@size" : "174520",
                                    "#cdata-section" : "https://aaa.yyy.com/docs/xml/708893eb-1fd9-4278-8b0e-e7e0738d8105.xml"
                                }, {
                                    "@type" : "HTML",
                                    "@size" : "46105",
                                    "#cdata-section" : "https://aaa.yyy.com/docs/html/708893eb-1fd9-4278-8b0e-e7e0738d8105.html"
                                }, {
                                    "@type" : "PDF",
                                    "@size" : "1270150",
                                    "#cdata-section" : "https://aaa.yyy.com/docs/pdf/708893eb-1fd9-4278-8b0e-e7e0738d8105.pdf"
                                }, {
                                    "@type" : "ALTERNATE PDF",
                                    "@size" : "60960",
                                    "#cdata-section" : "https://aaa.yyy.com/docs/version/708893eb-1fd9-4278-8b0e-e7e0738d8105.1577742297_short.pdf"
                                }
                            ]
                        }
                    ]
                }
            }, {
                "ContentData" : {
                    "@statusType" : "Published",
                    "@isReleased" : "Yes",
                    "@docId" : "22501",
                    "ProductStatus" : {
                        "@productCategory" : "Issuer",
                        "@focus" : "Issuer",
                        "Symbol" : [{
                                "@PrimarySymbol" : "AAA",
                                "@SecondarySymbol" : "Some name 1",
                                "@BmId" : "561"
                            }, {
                                "@PrimarySymbol" : "ABC",
                                "@SecondarySymbol" : "Some Name 2",
                                "@BmId" : "29"
                            }, {
                                "@PrimarySymbol" : "BBB",
                                "@SecondarySymbol" : "Some Name 3",
                                "@BmId" : "36"
                            }, {
                                "@PrimarySymbol" : "CCC",
                                "@SecondarySymbol" : "Some Name 4",
                                "@BmId" : "624"
                            }
                        ]
                    },
                    "ContentVersion" : {
                        "@versionId" : "1",
                        "@lastVersion" : "true",
                        "@lastPublished" : "true",
                        "Url" : [{
                                "@type" : "XML",
                                "@size" : "2706269",
                                "#cdata-section" : "https://aaa.yyy.com/docs/xml/1c420081-0ce5-4959-91d3-848bbbccd3e3.xml"
                            }, {
                                "@type" : "HTML",
                                "@size" : "32445",
                                "#cdata-section" : "https://aaa.yyy.com/docs/html/1c420081-0ce5-4959-91d3-848bbbccd3e3.html"
                            }, {
                                "@type" : "PDF",
                                "@size" : "887608",
                                "#cdata-section" : "https://aaa.yyy.com/docs/pdf/1c420081-0ce5-4959-91d3-848bbbccd3e3.pdf"
                            }, {
                                "@type" : "ALTERNATE PDF",
                                "@size" : "34366",
                                "#cdata-section" : "https://aaa.yyy.com/docs/shortPdf/1c420081-0ce5-4959-91d3-848bbbccd3e3.pdf"
                            }
                        ]
                    }
                }
            }
        ]
    }
}

我正在遵循中的代码示例。我想要 select 以下内容，但前提是 Symbol 部分中只有一个发行人并且最新版本的 PDF url：

@docId
@PrimarySymbol
@BmId
#cdata-section（但仅适用于最新版本的 PDF）

这是我的查询：

from content in jsonFeed.SelectTokens("DataFeed.Content").SelectMany(i => i.ObjectsOrSelf())
let issuer = content
        .SelectToken("ContentData.ProductStatus.@productCategory")
        .SingleOrMultiple()
        .Select(t => (string)t)
        .ToArray()
where issuer.FirstOrDefault().Equals("Issuer")
select new 
{
    DocID = (string)content.SelectToken("ContentData.@docId"),
    Symbol = (string)content.SelectToken("ContentData.ProductStatus.Symbol.@PrimarySymbol"),
    BMId = (int)content.SelectToken("ContentData.ProductStatus.Symbol.@BmId"),
    PDFUrl = (string)content.SelectToken("ContentData.ContentVersion.Url[3].#cdata-section")
}).ToList();

现在，我可以成功获取 Google 的所有字段，但我无法获取 Apple 的 PDFUrl（因为我不知道如何获取最新版本）。另外，我怎样才能完成我的 Where 子句，以便它只 select 带有 1 个符号的文档？所以，最后，我的列表将是下图：

Answer 1

您可以组合 let and where 来计算和筛选中间结果。

以下查询使用此技术，并且还查询 @type 等于 "PDF" 的 URL 而不是将其硬编码为索引 3（它实际上在索引 2 , 顺便说一下):

string pdfUrlType = "PDF";
var query =
    (from content in jsonFeed.SelectTokens("DataFeed.Content").SelectMany(i => i.ObjectsOrSelf())
     let issuer = content
             .SelectToken("ContentData.ProductStatus.@productCategory")
             .SingleOrMultiple()
             .Select(t => (string)t)
             .ToArray()
     where issuer.FirstOrDefault().Equals("Issuer")
     // Get the @PrimarySymbol where there is exactly one, or null otherwise.
     let symbol = (string)content.SelectToken("ContentData.ProductStatus.Symbol.@PrimarySymbol")
     // Skip content without a single primary symbol
     where symbol != null
     // Get the last ContentVersion record in the JSON document.
     let lastContentVersion = content
        .SelectToken("ContentData.ContentVersion")
        .SingleOrMultiple()
        .Where(v => (bool?)v.SelectToken("@lastVersion") == true)
        .LastOrDefault()
     // Skip content with no ContentVersion
     where lastContentVersion != null
     // Get the PDF Url record
     let pdfUrl = lastContentVersion.SelectToken("Url")
        .SingleOrMultiple()
        .Where(u => (string)u.SelectToken("@type") == pdfUrlType)
        .FirstOrDefault()
     // Skip content with no PDF Url record
     where pdfUrl != null
     select new
     {
         DocID = (string)content.SelectToken("ContentData.@docId"),
         Symbol = symbol,
         BMId = (int?)content.SelectToken("ContentData.ProductStatus.Symbol.@BmId"),
         PDFUrl = (string)pdfUrl.SelectToken("#cdata-section")
     }).ToList();

如果您确实想要备用 PDF url，请设置

string pdfUrlType = "ALTERNATE PDF";

样本fiddle.

如果您确定每条 "Content" 记录中 ContentVersion 的最新版本（"@lastVersion" 等于 "true" 的记录）保证是最后一个按文档顺序，可以简化查询如下：

     let lastContentVersion = content
        .SelectToken("ContentData.ContentVersion")
        .SingleOrMultiple()
        .LastOrDefault()

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