定义一个接口，包含两个方法：实体转xml 和 xml转实体。包含一个属性根节点标签名称

  /// <summary>
    /// 定义元属性实体类与Xml之间的转换接口
    /// </summary>
    /// <typeparam name="T">元属性实体类</typeparam>
    public interface IEntitySerialization<T>
    {
        /// <summary>
        /// 将实体类<c>T</c>使用<see cref="XmlWriter"/>转为XML 数据写到流、文件、文本
        /// 读取器或字符串。
        /// </summary>
        /// <param name="writer"><see cref="XmlWriter"/>实例</param>
        void WriteXml(XmlWriter writer);

        /// <summary>
        /// 将<see cref="XmlNode"/>节点的信息转为实体类<c>T</c>
        /// </summary>
        /// <param name="node"><see cref="XmlNode"/>实例，该实例包含了<c>T</c>
        /// 实体类所需要的信息</param>
        /// <returns>实体类<c>T</c></returns>
        T GetObject(XmlNode node);

        /// <summary>
        /// 根节点元素标签名称
        /// </summary>
        string RootElementName { get; }
    }

并实现具体实体对应的xml和实体之间的转化方式

 public class Hape : IEntitySerialization<Hape >
    {
        /// <summary>
        /// 名称
        /// </summary>
        public string Name { get; set; }
        /// <summary>
        /// 空间坐标 WKT格式
        /// </summary>
        public string Geometry { get; set; }

        /// <summary>
        /// 实体转xml
        /// </summary>
        /// <param name="writer"></param>
        public void WriteXml(XmlWriter writer)
        {
            writer.WriteStartElement(this.RootElementName);
            XmlHelper.WriteOptionalAttribute(writer,"name",Name);
            XmlReader reader = XmlReader.Create(new StringReader(DbGeography.FromText(Geometry).AsGml()));
            var gml = Deserialize(reader);
            Serialize(writer,gml);
            writer.WriteEndElement();
        }

        /// <summary>
        /// xml转实体
        /// </summary>
        /// <param name="node"></param>
        /// <returns></returns>
        public Hape GetObject(XmlNode node)
        {
            if (node == null)
            {
                throw new ArgumentNullException(nameof(node));
            }
            if (node.Name != this.RootElementName)
            {
                throw new ArgumentException("The element name of node is not " + RootElementName);
            }
            var name = XmlHelper.GetOptionalAttributeValue(node,"name");
            var gml = node.InnerXml.Replace("gml:","").Replace(":gml","");
            var geometry = DbGeography.FromGml(gml).AsText();
            return new Shape { Name = name,Geometry = geometry };
        }
        /// <summary>
        /// 根节点标签名称
        /// </summary>
        public string RootElementName => "Hape";
    }

    /// <summary>
    /// 集合
    /// </summary>
    public class HapeCollection : List<Hape>,IEntitySerialization<HapeCollection>
    {
        /// <summary>
        /// 实体转xml
        /// </summary>
        /// <param name="writer"></param>
        public void WriteXml(XmlWriter writer)
        {
            writer.WriteStartElement(this.RootElementName);
            XmlHelper.WriteEntityCollection(writer,this);
            writer.WriteEndElement();
        }

        /// <summary>
        /// xml转实体
        /// </summary>
        /// <param name="node"></param>
        /// <returns></returns>
        public HapeCollection GetObject(XmlNode node)
        {
            var result = new HapeCollection();
            var shapeList = XmlHelper.GetEntityCollection<Shape>(node,new hape().RootElementName);
            result.AddRange(shapeList);
            return result;
        }
        /// <summary>
        /// 根节点标签名称
        /// </summary>
        public string RootElementName => "Hapes";
    }

当每个实体都实现了xml和实体之间的转化，就很容易将这些实体组合成一个复杂的实体，并且转化方法可以很简单。

下面进行测试查看

给hapeCollection 赋值

            var hape = new Hape() { Name = "口",Geometry = "POINT(4 6)" };
            var hape2 = new Hape() { Name = "地",Geometry = "LINESTRING(47 -122.36 47 -122.343)" };
            var hape3 = new Hape()
            {
                Name = "造",Geometry = "POLYGON ((36 108 391 10 36 108 36 108 361 108))"
            };
            Hapes.Add(hape3);
            Hapes.Add(hape2);
            Hapes.Add(hape);

 public void TestHapeCollection()
        {
            var result = "";
            using (MemoryStream ms = new MemoryStream())
            {
                using (XmlWriter writer = XmlHelper.GetXmlWriter(ms))
                {
                    Shapes.WriteXml(writer);
                }
                result = Encoding.UTF8.GetString(ms.ToArray());
                var obj = GetObject<HapeCollection>(result);
            }
        }

<Hapes>
  <Hape name="造">
    <gml:Polygon>
      <gml:exterior>
        <gml:LinearRing>
          <gml:posList>36 108 391 10 36 108 36 108 361 108</gml:posList>
        </gml:LinearRing>
      </gml:exterior>
    </gml:Polygon>
  </Hape>
  <Hape name="地">
    <gml:LineString">
      <gml:posList>47 -122.36 47 -122.343</gml:posList>
    </gml:LineString>
  </Hape>
  <Hape name="口">
    <gml:Point>
      <gml:pos>6 4</gml:pos>
    </gml:Point>
  </Hape>
</Hapes>