Question

我有一个XML队列，通过linq读取如下：示例XML

    List<String> PlanInfo = new List<string>();
    XDocument xdoc = null;
    XNamespace ns = null;
    try
    {
        //List<String> PlanValuesList = new List<string>();
        xdoc = XDocument.Load(gLink);
        ns = xdoc.Root.Name.Namespace;

        var test = (
            from planInfo in xdoc.Descendants(ns + "Plan").Descendants(ns + "Eigenschappen")
            from Onderdelen in xdoc.Descendants(ns + "Onderdelen")
            select new
            {
                Naam = (string)planInfo.Element(ns + "Naam").Value ?? string.Empty,
                Type = (string)planInfo.Element(ns + "Type").Value ?? string.Empty,
                Status = (string)planInfo.Element(ns + "Status").Value ?? string.Empty,
                Datum = (Convert.ToString(planInfo.Element(ns + "Datum").Value).IndexOf("T") > 0) ? (string)planInfo.Element(ns + "Datum").Value.Substring(0, Convert.ToString(planInfo.Element(ns + "Datum").Value).IndexOf("T")) : (string)planInfo.Element(ns + "Datum").Value ?? string.Empty,
                Versie = (string)(planInfo.Element("VersieIMRO") ?? planInfo.Element("VersieGML")) ?? string.Empty,//Convert.ToString(planInfo.Element(ns + "VersieIMRO").Value) ?? String.Empty,
                VersiePraktijkRichtlijn = (string)planInfo.Element(ns + "VersiePraktijkRichtlijn").Value ?? string.Empty,
                BasisURL = (string)Onderdelen.Attribute("BasisURL")
            }).ToList();

        foreach (var item in test)
        {
            PlanInfo.Add(item.Naam);
            PlanInfo.Add(item.Type);
            PlanInfo.Add(item.Status);
            PlanInfo.Add(item.Datum);
            PlanInfo.Add(item.Versie);
            PlanInfo.Add(item.VersiePraktijkRichtlijn);
            PlanInfo.Add(item.BasisURL);
        }
 }
    catch (Exception ex)
    {
        //Error reading GeleideFormulier link for the plan and manifest
        throw;//Just throwing error here, as it is catched in the called method.
    }

    return PlanInfo;

C＃代码

 $(document).ready(function() {
  Stripe.setPublishableKey($('meta[name="stripe-key"]').attr('content'));
  // Watch for a form submission:
  $("#form-submit-btn").click(function(event) {
    event.preventDefault();
    $('input[type=submit]').prop('disabled', true);
    var error = false;
    var ccNum = $('#card_number').val(),
        cvcNum = $('#card_code').val(),
        expMonth = $('#card_month').val(),
        expYear = $('#card_year').val();

    if (!error) {
      // Get the Stripe token:
      Stripe.createToken({
        number: ccNum,
        cvc: cvcNum,
        exp_month: expMonth,
        exp_year: expYear
      }, stripeResponseHandler);
    }
    return false;
  }); // form submission

  function stripeResponseHandler(status, response) {
    // Get a reference to the form:
    var f = $("#new_user");

    // Get the token from the response:
    var token = response.id;

    // Add the token to the form:
    f.append('<input type="hidden" name="user[stripe_card_token]" value="' + token + '" />');

    // Submit the form:
    f.get(0).submit(); 
  }
});

在一些XML文件中＆＃34; versieIMRO＆＃34; tag变为＆＃34; versieGML＆＃34;，它给出了错误，因为Object Reference未设置为对象的实例。

请让我知道如何检查是否有＆＃34; versieGML＆＃34;标签代替＆＃34; versieIMRO＆＃34;？或者，如果其他XML中的标记名称不同，那么如何处理它？</ p>

Answer 1

您希望将XElement转换为字符串（而不是XElement.Value类型的string属性），以避免在找不到该元素的情况下使用NRE：

Version = (string)x.Element("version"),

如果您想在找不到versionX元素的情况下使用version，请尝试以下方式：

Version = (string)(x.Element("version") ?? x.Element("versionX")),

再一次，将Value属性转换为string是没用的，它没有任何区别。如果您想获得string.Empty而不是null，请再次使用null-coalescing运算符：

Version = (string)(x.Element("version") ?? x.Element("versionX")) ?? string.Empty,

LINQ读取XML到List为未知节点提供了对象引用？

1 个答案: