为什么在创建带有前缀和命名空间的元素时，根据元素是否嵌套，XmlWriter会给出不同的结果

Question

我需要生成以下输出：

<complement12:Complement xsi:schemaLocation="http://www.example.com/complement12 http://www.example.com/sub/files/complement12.xsd" version="1.1" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:complement12="http://www.example.com/complement12" />

我是这样做的：

var settings = new XmlWriterSettings {Indent = true};

    using (var sw = new StringWriter())
    {
        using (var writer = XmlWriter.Create(sw, settings))
        {
            writer.WriteStartDocument();

                writer.WriteStartElement("complement12", "Complement", @"http://www.example.com/complement12");                

                writer.WriteAttributeString("xsi", "schemaLocation", "http://www.w3.org/2001/XMLSchema-instance",
                    "http://www.example.com/complement12 http://www.example.com/sub/files/complement12.xsd");

                writer.WriteAttributeString("version", "1.1");

                writer.WriteEndElement();

            writer.WriteEndDocument();
        }

        Console.WriteLine(sw);
    }

但是这个元素应该是嵌套的，我是这样做的：

var settings = new XmlWriterSettings {Indent = true};

    using (var sw = new StringWriter())
    {
        using (var writer = XmlWriter.Create(sw, settings))
        {
            writer.WriteStartDocument();

            writer.WriteStartElement("doc", "Document", @"http://www.example.com/sub");

                writer.WriteAttributeString("xsi", "schemaLocation", "http://www.w3.org/2001/XMLSchema-instance",
                    "http://www.example.com/sub http://www.example.com/sub/files/doc20.xsd");

                writer.WriteStartElement("complement12", "Complement", @"http://www.example.com/complement12");                

                writer.WriteAttributeString("xsi", "schemaLocation", "http://www.w3.org/2001/XMLSchema-instance",
                    "http://www.example.com/complement12 http://www.example.com/sub/files/complement12.xsd");

                writer.WriteAttributeString("version", "1.1");

                writer.WriteEndElement();

            writer.WriteEndElement();

            writer.WriteEndDocument();
        }

        Console.WriteLine(sw);
    }

我不知道为什么，嵌套元素的结果是不同的，因为没有生成属性"xmlns:xsi“。

<doc:Document xsi:schemaLocation="http://www.example.com/sub http://www.example.com/sub/files/doc20.xsd" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:doc="http://www.example.com/sub"><complement12:Complement xsi:schemaLocation="http://www.example.com/complement12 http://www.example.com/sub/files/complement12.xsd" version="1.1" xmlns:complement12="http://www.example.com/complement12" />

​

小提琴here中的示例。

Answer 1

xsi前缀是在父节点中定义的，因此编写器省略了继承的前缀定义。