c# - 从 XPathNavigator.AppendChild() 创建时如何设置 XmlWriter.XmlWriterSettings？

Question

我需要将 XmlWriter 的 XmlWriterSettings 的 OmitXmlDeclaration 属性设置为 false 以不创建 XML 声明。问题是我通过调用 XPathNavigator.AppendChild() 方法创建了 XmlWriter。代码如下:

    public String GetEntityXml<T>(List<T> entities)
    {
        XmlDocument xmlDoc = new XmlDocument();
        XPathNavigator nav = xmlDoc.CreateNavigator();

        using (XmlWriter writer = nav.AppendChild())
        {

            XmlSerializer ser = new XmlSerializer(typeof(List<T>), new XmlRootAttribute(typeof(T).Name + "_LIST"));
            ser.Serialize(writer, entities);
        }

        StringWriter stringWriter = new StringWriter();
        XmlTextWriter xmlTextWriter = new XmlTextWriter(stringWriter);

        xmlDoc.WriteTo(xmlTextWriter);

        string resultString = stringWriter.ToString();

        stringWriter.Close();
        xmlTextWriter.Close();

        return resultString;
    }

知道如何序列化 List 而没有 XML 声明吗？

Answer 1

当我执行你的代码时，我没有得到 XML 声明。序列化 List<int>给我:

<Int32_LIST xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
            xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <int>5</int>
  <int>7</int>
  <int>2</int>
</Int32_LIST>

请注意 OmitXmlDeclaration 的“XML 声明”指的是通常类似于:

<?xml version="1.0" encoding="UTF-8" ?>

如果您指的是 xmlns部分，那么这些被称为“XML namespace declarations”，并且可以通过初始化 XmlSerializerNamespaces 来消除。具有默认空 namespace 的实例，并将其传递给您的 Serialize方法:

XmlSerializer ser = new XmlSerializer(typeof(List<T>), new XmlRootAttribute(typeof(T).Name + "_LIST"));
var namespaces = new XmlSerializerNamespaces(new[] { new XmlQualifiedName("", "") });
ser.Serialize(writer, entities, namespaces);

下面是一个缩短的实现，它实现了与您的代码相同的结果:

public String GetEntityXml<T>(List<T> entities)
{
    var sb = new StringBuilder();
    var settings = new XmlWriterSettings { OmitXmlDeclaration = true };
    using (XmlWriter writer = XmlWriter.Create(sb, settings))
    {
        XmlSerializer ser = new XmlSerializer(typeof(List<T>), new XmlRootAttribute(typeof(T).Name + "_LIST"));
        var namespaces = new XmlSerializerNamespaces(new[] { new XmlQualifiedName("", "") });
        ser.Serialize(writer, entities, namespaces);
    }
    return sb.ToString();
}