.NET中解析含双命名空间的XML并反序列化至对象的问题

XML中ServiceResponse和ServiceResult下的子元素分属不同命名空间，现有C#类未正确处理命名空间，导致反序列化后EmployeeDto的属性值为空。

XML示例 #

<ServiceResponse xmlns="http://www.julianuslemurrex.com/MyWcfService/2023/9/19">
    <ServiceResult xmlns:a="http://schemas.datacontract.org/2023/9/MyWcfService.Model.DataTransfer" xmlns:i="http://www.w3.org/2001/XMLSchema-instance">
        <a:IsEmployee i:nil="true"/>
        <a:IsContractor i:nil="true"/>
        <a:EmployeeReference>EMEM001F1</a:EmployeeReference>
    </ServiceResult>
</ServiceResponse>

原错误代码 #

C#类定义 #

[XmlRoot(ElementName="ServiceResponse")]
public class EmployeeDtoRoot
{
    [XmlElement(ElementName="ServiceResult")]
    public EmployeeDto Root { get; set; }
}

[XmlRoot("ServiceResult")]
public class EmployeeDto
{
    [XmlElement("IsEmployee")]
    public bool IsEmployee { get; set; }

    [XmlElement("IsContractor")]
    public bool IsContractor { get; set; }

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

反序列化代码 #

using (XmlTextReader xtr = new XmlTextReader(xmlToDeserialize))
{
    XmlSerializer serializer = new XmlSerializer(typeof(EmployeeDtoRoot));
    
    xtr.Namespaces = false;
    xtr.DtdProcessing = DtdProcessing.Parse;
    var root = (EmployeeDtoRoot)serializer.Deserialize(xtr);
    var r = root;
}

解决方案 #

方案1：修正类的Xml特性，正确处理命名空间 #

需要为对应元素指定匹配的命名空间，同时用可空类型接收带有i:nil="true"的元素。

修改后的C#类：

[XmlRoot(ElementName = "ServiceResponse", Namespace = "http://www.julianuslemurrex.com/MyWcfService/2023/9/19")]
public class EmployeeDtoRoot
{
    [XmlElement(ElementName = "ServiceResult")]
    public EmployeeDto Root { get; set; }
}

public class EmployeeDto
{
    [XmlElement(ElementName = "IsEmployee", Namespace = "http://schemas.datacontract.org/2023/9/MyWcfService.Model.DataTransfer")]
    public bool? IsEmployee { get; set; }

    [XmlElement(ElementName = "IsContractor", Namespace = "http://schemas.datacontract.org/2023/9/MyWcfService.Model.DataTransfer")]
    public bool? IsContractor { get; set; }

    [XmlElement(ElementName = "EmployeeReference", Namespace = "http://schemas.datacontract.org/2023/9/MyWcfService.Model.DataTransfer")]
    public string EmployeeReference { get; set; }
}

调整后的反序列化代码（无需关闭命名空间）：

using (var stringReader = new StringReader(xmlToDeserialize))
using (XmlTextReader xtr = new XmlTextReader(stringReader))
{
    XmlSerializer serializer = new XmlSerializer(typeof(EmployeeDtoRoot));
    xtr.DtdProcessing = DtdProcessing.Parse;
    var root = (EmployeeDtoRoot)serializer.Deserialize(xtr);
    // root.Root的属性会被正确赋值
}

方案2：直接提取目标元素值（无需定义完整类） #

如果仅需要IsEmployee、IsContractor、EmployeeReference三个值，用LINQ to XML直接查询更高效：

XDocument doc = XDocument.Parse(xmlToDeserialize);
// 定义命名空间
XNamespace aNs = "http://schemas.datacontract.org/2023/9/MyWcfService.Model.DataTransfer";
XNamespace iNs = "http://www.w3.org/2001/XMLSchema-instance";

// 处理IsEmployee
var isEmployeeElem = doc.Descendants(aNs + "IsEmployee").FirstOrDefault();
bool? isEmployee = isEmployeeElem?.Attribute(iNs + "nil")?.Value == "true" ? null : isEmployeeElem?.Value != null ? bool.Parse(isEmployeeElem.Value) : null;

// 处理IsContractor
var isContractorElem = doc.Descendants(aNs + "IsContractor").FirstOrDefault();
bool? isContractor = isContractorElem?.Attribute(iNs + "nil")?.Value == "true" ? null : isContractorElem?.Value != null ? bool.Parse(isContractorElem.Value) : null;

// 处理EmployeeReference
string employeeReference = doc.Descendants(aNs + "EmployeeReference").FirstOrDefault()?.Value;

核心注意点 #

• 命名空间必须严格匹配：XML中a:前缀对应的命名空间必须在代码中明确指定，否则序列化器无法识别元素。
• 可空类型适配nil属性：带有i:nil="true"的元素表示值不存在，必须用可空类型（bool?）接收，否则会触发反序列化异常。
• LINQ to XML更适合临时需求：如果不需要完整的对象结构，直接查询元素可以省去类定义的工作量，更适合临时解决方案。

内容的提问来源于stack exchange，提问作者julianuslemurrex