在類中使用數組進行XML反序列化

Question

我正在嘗試反序列化一串XML數據。 但是我沒有在反序列化函數返回的對象中找回數據。

以下是類定義：

[XmlType("STATE-COUNTY-RECORDS")]
public class StateCountyRecords
{
    [XmlElement("TOTAL")]
    public int Total { get; set; }

    [XmlElement("LIMIT")]
    public int Limit { get; set; }

    [XmlElement("OFFSET")]
    public int Offset { get; set; }

    [XmlArray("STATE-COUNTY-ARRAY"), XmlArrayItem("STATE-COUNTY")]
    public StateCounty[] StateCountyArray { get; set; }

    public StateCountyRecords() {}

    public StateCountyRecords(int total, int limit, int offset, int[] id, string[] fips_code, string[] state, string[] name)
    {
        Total = total;
        Limit = limit;
        Offset = offset;

        var count = id.Length;
        StateCountyArray = new StateCounty[count];
        for (int i = 0; i < count; i++)
        {
            StateCountyArray[i] = new StateCounty(id[i], fips_code[i], state[i], name[i]);
        }
    }
}

public class StateCounty
{
    [XmlElement("ID")]
    public int Id { get; set; }

    [XmlElement("FIPS-CODE")]
    public string Fips_Code { get; set; }

    [XmlElement("STATE")]
    public string State { get; set; }

    [XmlElement("NAME")]
    public string Name { get; set; }

    public StateCounty(int id, string fips_code, string state, string name)
    {
        Id = id;
        Fips_Code = fips_code;
        State = state;
        Name = name;
    }

    public StateCounty() { }
}

這是xml字符串數據：

<?xml version=\"1.0\" encoding=\"UTF-8\"?>
<STATE-COUNTY-FILE xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\">
<STATE-COUNTY-RECORDS>
    <TOTAL>3314</TOTAL>
    <LIMIT>10</LIMIT>
    <OFFSET>0</OFFSET>
    <STATE-COUNTY-ARRAY>
    <STATE-COUNTY>
        <ID>1</ID>
        <FIPS-CODE>01000</FIPS-CODE>
        <STATE>AL</STATE>
        <NAME>Alabama</NAME>
    </STATE-COUNTY>
    <STATE-COUNTY>
        <ID>2</ID>
        <FIPS-CODE>01001</FIPS-CODE>
        <STATE>AL</STATE>
        <NAME>Autauga</NAME>
    </STATE-COUNTY>
    <STATE-COUNTY>
        <ID>3</ID>
        <FIPS-CODE>01003</FIPS-CODE>
        <STATE>AL</STATE>
        <NAME>Baldwin</NAME>
    </STATE-COUNTY>
    </STATE-COUNTY-ARRAY>
</STATE-COUNTY-RECORDS>
</STATE-COUNTY-FILE>

以下是反序列化xml字符串的函數：

    public static StateCountyRecords DeserializeStateCountyData(string xmlString)
    {
        XmlSerializer mySerializer = new XmlSerializer(typeof(StateCountyRecords), new XmlRootAttribute("STATE-COUNTY-FILE"));
        using (XmlReader myXmlReader = XmlReader.Create(new StringReader(xmlString)))
        {
            StateCountyRecords rslt;
            rslt = (StateCountyRecords)mySerializer.Deserialize(myXmlReader);
        }
    }
}

我得到的rslt不包含Total和Limit的數據，Offset all為0，StateCountyArray為null。 我沒有得到任何錯誤。 我通過以下方式確保xml有效：

if (myXmlReader.CanResolveEntity && myXmlReader.CanReadValueChunk && myXmlReader.CanReadBinaryContent)
                rslt = (StateCountyRecords)mySerializer.Deserialize(myXmlReader);

我想知道我的類定義的XmlElement和XML文件之間是否存在不匹配。

Answer 1

您的問題是您的XML有一個外部元素，在您的數據模型中沒有考慮，即<STATE-COUNTY-FILE>元素：

<STATE-COUNTY-FILE xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <STATE-COUNTY-RECORDS>
    <!-- Various elements under StateCountyRecords -->
  </STATE-COUNTY-RECORDS>
</STATE-COUNTY-FILE>

由於數據模型的根是StateCountyRecords ，因此沒有任何內容與此最外層元素相對應。 您嘗試使用new XmlRootAttribute("STATE-COUNTY-FILE")解決此問題，但是這只會重命名外部元素，而不是添加額外的嵌套級別。

相反，您需要為此目的引入外部容器POCO：

[XmlType("STATE-COUNTY-FILE")]
public class StateCountyFile
{
    [XmlElement("STATE-COUNTY-RECORDS")]
    public StateCountyRecords StateCountyRecords { get; set; }
}

並反序列化如下：

    public static StateCountyRecords DeserializeStateCountyData(string xmlString)
    {
        var mySerializer = new XmlSerializer(typeof(StateCountyFile));
        using (var myXmlReader = XmlReader.Create(new StringReader(xmlString)))
        {
            var rslt = (StateCountyFile)mySerializer.Deserialize(myXmlReader);
            return rslt.StateCountyRecords;
        }
    }

或者，您可以手動前進XmlReader直到遇到名為<STATE-COUNTY-RECORDS>的元素，並反序列化：

    public static StateCountyRecords DeserializeStateCountyData(string xmlString)
    {
        return XmlTypeExtensions.DeserializeNestedElement<StateCountyRecords>(xmlString);
    }

使用擴展方法：

public static class XmlTypeExtensions
{
    public static T DeserializeNestedElement<T>(string xmlString)
    {
        var mySerializer = new XmlSerializer(typeof(T));
        var typeName = typeof(T).XmlTypeName();
        var typeNamespace = typeof(T).XmlTypeNamespace();

        using (var myXmlReader = XmlReader.Create(new StringReader(xmlString)))
        {
            while (myXmlReader.Read())
                if (myXmlReader.NodeType == XmlNodeType.Element && myXmlReader.Name == typeName && myXmlReader.NamespaceURI == typeNamespace)
                {
                    return (T)mySerializer.Deserialize(myXmlReader);
                }
            return default(T);
        }
    }

    public static string XmlTypeName(this Type type)
    {
        var xmlType = type.GetCustomAttribute<XmlTypeAttribute>();
        if (xmlType != null && !string.IsNullOrEmpty(xmlType.TypeName))
            return xmlType.TypeName;
        return type.Name;
    }

    public static string XmlTypeNamespace(this Type type)
    {
        var xmlType = type.GetCustomAttribute<XmlTypeAttribute>();
        if (xmlType != null && !string.IsNullOrEmpty(xmlType.Namespace))
            return xmlType.Namespace;
        return string.Empty;
    }
}

順便提一下，通過在內存中創建類的實例，對其進行序列化，然后將生成的XML與輸入XML進行比較，可以輕松診斷出諸如此類的反序列化問題。 通常問題很明顯。