Question

我正在将xml解析为变量，如此

void myClient_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e)
        {
         if (e.Error == null)
            {
                XElement currencyElements = XElement.Parse(e.Result);

                XNamespace gesmes = "http://www.gesmes.org/xml/2002-08-01";
                XNamespace ns = "http://www.ecb.int/vocabulary/2002-08-01/eurofxref";

                usd=Convert.ToDouble(currencyElements.Descendants(ns +"Cube")
                .Where(x=>x.Attribute("currency")!=null)             
                .Where(x => x.Attribute("currency")
                .Value == "USD")
                .Select(x => new ClassRates
                {
                    usd=Convert.ToDouble(x.Attribute("rate").Value)  
                }));


            else
            {
                textBlock1.Text = e.Error.ToString();
            }
}

这是我的班级ClassRates

public class ClassRates
        {
            public String curName { get; set; }
            public double curRate { get; set; }

            public double usd, jpy, bgn, czk, dkk, 
            gbp, huf, ltl, lvl, pln, ron, sek, chf, nok,
            hrk, rub, try1, aud, brl, cad, cny, hkd, idr, 
            ils, inr, krw, mxn, myr, nzd, php, sgd, thb, zar;
        }

变量usd在解析块之外不可用于计算。这是因为我正在通过课程选择项目进行解析吗？有工作吗？试图为要存储的速率实现字典/列表/数组，但也无法正常工作，这是我尝试使用字典的版本

Dictionary<string, double> rates = new Dictionary<string, double>();
                String xml = e.Result;
                XElement doc = XElement.Parse(xml);
                XNamespace ns = XNamespace.Get("http://www.gesmes.org/xml/2002-08-01");
                XNamespace masterNs = XNamespace.Get("http://www.ecb.int/vocabulary/2002-08-01/eurofxref");

                doc.Element(ns.GetName("Envelope"))
                   .Element(masterNs.GetName("Cube"))
                   .Elements(masterNs.GetName("Cube"))
                   .ToList().ForEach(cube =>
                   {

                       var cubeCurrencies = cube.Descendants(masterNs.GetName("Cube"));

                       cubeCurrencies.ToList().ForEach(currency =>
                       {
                           var country = currency.Attribute("currency").Value;
                           var rate = currency.Attribute("rate").Value;

                           rates.Add(country, double.Parse(rate));
                       });

                   });

这导致我找不到的NullReferenceException。欢迎任何想法，

    <gesmes:Envelope xmlns:gesmes="http://www.gesmes.org/xml/2002-08-01" xmlns="http://www.ecb.int/vocabulary/2002-08-01/eurofxref">
<gesmes:subject>Reference rates</gesmes:subject>
<gesmes:Sender>
  <gesmes:name>European Central Bank</gesmes:name>
</gesmes:Sender>
<Cube>
  <Cube time="2012-04-12">
    <Cube currency="USD" rate="1.3153"/>
    <Cube currency="JPY" rate="106.54"/>
    <Cube currency="BGN" rate="1.9558"/>
    <Cube currency="CZK" rate="24.803"/>
    <Cube currency="DKK" rate="7.4384"/>
    <Cube currency="GBP" rate="0.82470"/>
    <Cube currency="HUF" rate="296.90"/>
    <Cube currency="LTL" rate="3.4528"/>
    <Cube currency="LVL" rate="0.6989"/>
    <Cube currency="PLN" rate="4.1802"/>
    <Cube currency="RON" rate="4.3745"/>
    <Cube currency="SEK" rate="8.8912"/>
    <Cube currency="CHF" rate="1.2027"/>
    <Cube currency="NOK" rate="7.6100"/>
    <Cube currency="HRK" rate="7.4758"/>
    <Cube currency="RUB" rate="38.7840"/>
    <Cube currency="TRY" rate="2.3664"/>
    <Cube currency="AUD" rate="1.2645"/>
    <Cube currency="BRL" rate="2.4075"/>
    <Cube currency="CAD" rate="1.3132"/>
    <Cube currency="CNY" rate="8.2961"/>
    <Cube currency="HKD" rate="10.2128"/>
    <Cube currency="IDR" rate="12055.30"/>
    <Cube currency="ILS" rate="4.9348"/>
    <Cube currency="INR" rate="67.8550"/>
    <Cube currency="KRW" rate="1500.58"/>
    <Cube currency="MXN" rate="17.2124"/>
    <Cube currency="MYR" rate="4.0360"/>
    <Cube currency="NZD" rate="1.6001"/>
    <Cube currency="PHP" rate="56.176"/>
    <Cube currency="SGD" rate="1.6507"/>
    <Cube currency="THB" rate="40.564"/>
    <Cube currency="ZAR" rate="10.4472"/>
</Cube>
</Cube>
</gesmes:Envelope>

MH

Answer 1

在ClassRate中创建myClient_DownloadStringCompleted的本地实例并引用它，而不是在Linq查询完成时创建新实例。

另外，请重构您的解析代码以及ClassRates。分离Linq语句，创建一个解析方法，可以将货币类型作为参数，然后根据它执行查询。

Answer 2

http://msdn.microsoft.com/en-us/library/system.runtime.serialization.datacontractserializer%28v=vs.95%29.aspx

以下是两种反序列化xml twitter feed的方法示例。您还需要设置类，并使用[DataContract]和[DataMember]属性对它们进行装饰。我希望这对你有所帮助。

如果您有时间，请查看json以获取您的Web服务。它往往具有更小的占用空间，这意味着通过线路发送的数据比xml更少，并且很容易反序列化。

    void myClient_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e)
    {
        var tweets = ReadToObject(e.Result);
        var tweets2 = ReadToObject2(e.Result);
    }

    private static statuses ReadToObject(string xml)
    {
        var tweets = new statuses();
        using (var ms = new MemoryStream(Encoding.UTF8.GetBytes(xml)))
        {
            var ser = new DataContractSerializer(typeof(statuses));
            tweets = ser.ReadObject(ms) as statuses;
        }
        return tweets;

    }

    private static statuses ReadToObject2(string xml)
    {
        XmlSerializer ser = new XmlSerializer(typeof(statuses));
        var tweets = new statuses();

        using(var stringReader = new StringReader(xml))
        {
            using (var xmlReader = new XmlTextReader(stringReader))
            {
                tweets = ser.Deserialize(xmlReader) as statuses;
            }
        }
        return tweets;
    }

如何在解析语句wp7之外使用类变量

2 个答案: