在自我之前获取元素

Question

如果当前的“名称”元素为空或为空，它应该采用前一个元素的“名称”值。第一个元素名称永远不会为 null 或为空。

我需要在当前“名称”元素值为空或为空的情况下获取之前的元素“名称”值：

List<ScripTbl> ScripData = ScrpHldNode.Descendants(ns + "Scrp").Select(x => new ScripTbl
{
    ID = sID,
    //need help with the line below....
    ScripShare = (!string.IsNullOrEmpty((String)x.Element(ns + "Name")) ? (String)x.Element(ns + "Name") : (x.ElementsBeforeSelf().Count() > 0 ? (String)x.ElementsBeforeSelf().Last().Element(ns + "Name") : "")),
    ScripOpenBalanceDue = (String)x.Element(ns + "OpBal"),
    ScripClosingBalance = (String)x.Element(ns + "ClBal"),
    ScripTransaction = (String)x.Element(ns + "Tran"),
    ScripMovement = (String)x.Element(ns + "Move"),
    ScripFooter = sScripFooter,
    Seq = x.ElementsBeforeSelf().Count() + 1,
    ScripSectorCode = (String)x.Element(ns + "SecCde"),
    ScripClosingPrice = (String)x.Element(ns + "ClPrce"),
    SplitIndicator = (!string.IsNullOrEmpty((String)x.Element(ns + "Name")) ? (x.ElementsBeforeSelf().Count() > 0 && (String)x.Element(ns + "Name") == (String)x.ElementsBeforeSelf().Last().Element(ns + "Name") ? "1" : "0") : "0")
}).ToList();

和 XML：

<ScrpHld xmlns="http://www.website.co.za/namespace">
<Scrp>
    <Name>Company Name Number 1</Name>
    <SecCde>1366J</SecCde>
    <Tran>SOLD</Tran>
    <OpBal>0</OpBal>
    <Move>-2000</Move>
</Scrp>
<Scrp>
    <Tran>ELECTRONIC SETTLEMENT</Tran>
    <Move>2000</Move>
    <ClPrce>25045.00</ClPrce>
    <ClBal>0</ClBal>
</Scrp>
<Scrp>
    <Name>Company Name Number 2</Name>
    <SecCde>1313J</SecCde>
    <Tran>SOLD</Tran>
    <OpBal>10000</OpBal>
    <Move>-90500</Move>
</Scrp>
<Scrp>
    <Tran>ELECTRONIC SETTLEMENT</Tran>
    <Move>80500</Move>
    <ClPrce>3392.00</ClPrce>
    <ClBal>0</ClBal>
</Scrp> 
</ScrpHld>

Answer 1

使用PreviousNode而不是ElementsBeforeSelf，会更容易。我分成多行只是为了增加答案的可读性。

该行应该与此类似

ScripShare = (x.Element(ns + "Name") != null 
                 ? (string)x.Element(ns + "Name")
                 : (x.PreviousNode != null
                          ? ((XElement)x.PreviousNode).Element(ns + "Name").Value
                          : string.Empty)),

如果您的 xml 将在元素中包含 cmets 或任何其他文本，您应该检查前一个节点的类型为 XElement 而不是注释 (XComent) 或文本 (XText)，然后在这种情况下使用ElementsBeforeSelf会很容易

ScripShare = (x.Element(ns + "Name") != null 
                     ? (string)x.Element(ns + "Name")
                     : (x.NodesBeforeSelf().Last(e => e.NodeType == XmlNodeType.Element) != null
                              ? ((XElement)x.NodesBeforeSelf().Last(e => e.NodeType == XmlNodeType.Element)).Element(ns + "Name").Value
                              : string.Empty)),

Answer 2

试试这个：

    private static string ns = "{http://www.website.co.za/namespace}";
    private static string getName(XElement x) {
        if (x == null)
            throw new InvalidOperationException("First elements has no Name");
        var val = (string) x.Element(ns + "Name");
        return val ?? getName((XElement)x.PreviousNode);
    }

    static void Main(string[] args)
    {
        string xml = @"<ScrpHld xmlns=""http://www.website.co.za/namespace"">
        <Scrp>
            <Name>Company Name Number 1</Name>
            <SecCde>1366J</SecCde>
            <Tran>SOLD</Tran>
            <OpBal>0</OpBal>
            <Move>-2000</Move>
        </Scrp>
        <Scrp>
            <Tran>ELECTRONIC SETTLEMENT</Tran>
            <Move>2000</Move>
            <ClPrce>25045.00</ClPrce>
            <ClBal>0</ClBal>
        </Scrp>
        <Scrp>
            <Name>Company Name Number 2</Name>
            <SecCde>1313J</SecCde>
            <Tran>SOLD</Tran>
            <OpBal>10000</OpBal>
            <Move>-90500</Move>
        </Scrp>
        <Scrp>
            <Tran>ELECTRONIC SETTLEMENT</Tran>
            <Move>80500</Move>
            <ClPrce>3392.00</ClPrce>
            <ClBal>0</ClBal>
        </Scrp> 
        </ScrpHld>";
        XDocument doc = XDocument.Parse(xml);
        var result = doc.Descendants(ns + "Scrp").Select(x => new
            {
                Name = getName(x)
            });
        foreach (var item in result)
        {
            Console.WriteLine(item.Name);
        }

此方法使用递归方法，因此即使两个连续元素没有名称，它们也会使用前一个元素的名称。

Answer 3

您可以声明用于在选择方法范围之外捕获当前名称的变量：

string name = "";
scripData = ScrpHldNode.Descendants(ns + "Scrp")
                       .Select(scrp => {
                            var currentName = (string)scrp.Element(ns + "Name");
                            if (!String.IsNullOrEmpty(currentName))
                                name = currentName;

                            return new ScripTbl {
                                ScripShare = name
                                // ...
                            };
                       });

没有递归，没有遍历先前元素的 xml 树。

---

如果您只需要检查缺少的名称元素，那么代码可以缩短为

string name = "";
var scripData = from scrp in ScrpHldNode.Descendants(ns + "Scrp")
                let currentName = (string)scrp.Element(ns + "Name") ?? name
                select new ScripTbl {
                     ScripShare = (name = currentName)
                     // ...
                };

它更短（由于在 ScripShare 分配期间使用空合并运算符和棘手的名称分配），但我会使用更长更明显的代码。