c# - .net XmlSerialize 抛出“无法在使用 ConformanceLevel.Fragment 创建的编写器上调用 WriteStartDocument”

Question

我试图序列化一个类，将一个 XML 文件作为多个片段写入，即将类的每个对象作为一个单独的片段写入，而不需要 XML 标头/根。下面是一个示例代码：

[Serializable]
public class Test
{
    public int X { get; set; }
    public String Y { get; set; }
    public String[] Z { get; set; }

    public Test()
    {
    }

    public Test(int x, String y, String[] z)
    {
        X = x;
        Y = y;
        Z = z;
    }
}

class Program
{
    static void Main(string[] args)
    {
        Test t1 = new Test(1, "t1", new[] { "a", "b" });
        Test t2 = new Test(2, "t2", new[] { "c", "d", "e" });

        XmlSerializer serializer = new XmlSerializer(typeof(Test));
        //using (StreamWriter writer = new StreamWriter(@"f:\test\test.xml"))
        {
            XmlWriter xmlWriter = XmlWriter.Create(@"f:\test\test.xml",
                                                   new XmlWriterSettings()
                                                       {ConformanceLevel = ConformanceLevel.Fragment,
                                                        OmitXmlDeclaration = true,
                                                        Indent = true});
            serializer.Serialize(xmlWriter, t1);
            serializer.Serialize(xmlWriter, t2);
            xmlWriter.Close();
        }
    }
}

在第一次调用序列化时，我得到了异常：

WriteStartDocument cannot be called on writers created with ConformanceLevel.Fragment

我在这里想念什么？

Answer 1

这个问题有一个解决方法。如果在使用序列化程序之前已经使用了 xml 编写器，则不会写入标头。以下确实有效，但会在 xml 文件的第一行添加一个空的注释标记

oleksa 建议的改进代码

static void Main(string[] args)
    {
        Test t1 = new Test(1, "t1", new[] { "a", "b" });
        Test t2 = new Test(2, "t2", new[] { "c", "d", "e" });

        XmlSerializer serializer = new XmlSerializer(typeof(Test));
        //using (StreamWriter writer = new StreamWriter(@"f:\test\test.xml"))
        {
            XmlWriter xmlWriter = XmlWriter.Create(@"test.xml",
                                                   new XmlWriterSettings()
                                                   {
                                                       ConformanceLevel = ConformanceLevel.Fragment,
                                                       OmitXmlDeclaration = false,
                                                       Indent = true,
                                                       NamespaceHandling = NamespaceHandling.OmitDuplicates
                                                   });
            xmlWriter.WriteWhitespace("");
            serializer.Serialize(xmlWriter, t1);
            serializer.Serialize(xmlWriter, t2);
            xmlWriter.Close();
        }
    }