C# 将 XML 文件转换为多个多边形对象

Question

将多个 MapInfo 文件转换为一个唯一的 Shapefile，然后再次将该文件转换为 .KML 后，我得到了以下 .XML 文件。我的想法是提取每组 'coordinates' 部分，并使用它们构建多边形。

其他尝试的解决方案：

鉴于面临这种阻塞的时间过长，我尝试获取每对 'coordinates' 标签并使用 Substring 获取坐标。不幸的是，鉴于文件的大小 (>400 MB)，这种肮脏的方法并不实用。

Xml 文件

<?xml version="1.0" encoding="UTF-8"?>
<kml xmlns="http://www.opengis.net/kml/2.2">
  <Document id="root_doc">
    <Schema id="PruebaKML4g.schema">
      <SimpleField name="FID" type="float"/>
      <SimpleField name="REGION" type="float"/>
      <SimpleField name="NOMBRE" type="string"/>
      <SimpleField name="layer" type="string"/>
      <SimpleField name="path" type="string"/>
    </Schema>
    <Document id="PruebaKML4g">
      <name>PruebaKML4g</name>
      <Placemark id="PruebaKML4g.1">
        <ExtendedData>
          <SchemaData schemaUrl="#PruebaKML4g.schema">
            <SimpleData name="FID">5</SimpleData>
            <SimpleData name="REGION">1</SimpleData>
            <SimpleData name="NOMBRE">BAJA CALIFORNIA</SimpleData>
            <SimpleData name="layer">LBS_REGION_1_region</SimpleData>
            <SimpleData name="path">C:/Files/LBS_REGION_1_region.shp</SimpleData>
          </SchemaData>
        </ExtendedData>
        <MultiGeometry>
         <Polygon>
            <outerBoundaryIs>
              <LinearRing>
                <coordinates>
                  -105.258751,21.782028,0
                  -105.247174,21.81173,0
                  -105.241826,21.809401,0
                  -105.236994,21.806241,0
                  -105.232822,21.802344,0
                  -105.229439,21.79783,0
                  -105.228552,21.796052,0
                  -105.228974,21.795899,0
                  -105.230294,21.79522,0
                  -105.231872,21.79511,0
                  -105.234048,21.79431,0
                  -105.235131,21.794083,0
                  -105.236824,21.793857,0
                  -105.238518,21.793295,0
                  -105.239365,21.792389,0
                  -105.240327,21.790914,0
                  -105.242379,21.79046,0
                  -105.243829,21.790459,0
                  -105.245644,21.788766,0
                  -105.247331,21.785709,0
                  -105.24817,21.783115,0
                  -105.248701,21.780372,0
                  -105.258751,21.782028,0
                </coordinates>
              </LinearRing>
            </outerBoundaryIs>
          </Polygon>        
...
            <Polygon>
            <outerBoundaryIs>
              <LinearRing>
                <coordinates>
                  -103.704559,20.767933,0
                  -103.702714,20.773608,0
                  -103.701694,20.77322,0
                  -103.700762,20.772672,0
                  -103.699944,20.77198,0
                  -103.699267,20.771165,0
                  -103.698751,20.770252,0
                  -103.698411,20.769268,0
                  -103.698258,20.768243,0
                  -103.698297,20.76721,0
                  -103.704559,20.767933,0
                </coordinates>
              </LinearRing>
            </outerBoundaryIs>
          </Polygon>
          <Polygon>
            <outerBoundaryIs>
              <LinearRing>
                <coordinates>
                  -105.160778,20.766278,0
                  -105.162411,20.77201,0
                  -105.161328,20.77219,0
                  -105.160228,20.77219,0
                  -105.159145,20.77201,0
                  -105.158111,20.771656,0
                  -105.157159,20.771139,0
                  -105.156317,20.770474,0
                  -105.15561,20.769682,0
                  -105.15506,20.768786,0
                  -105.160778,20.766278,0
                </coordinates>
              </LinearRing>
            </outerBoundaryIs>
          </Polygon>          
          <Polygon>
            <outerBoundaryIs>
              <LinearRing>
                <coordinates>
                  -117.125814,32.524285,0
                  -117.125516,32.524512,0
                  -117.125142,32.524428,0
                  -117.124876,32.524169,0
                  -117.124754,32.524513,0
                  -117.124784,32.525361,0
          </coordinates>
              </LinearRing>
            </outerBoundaryIs>
          </Polygon>
        </MultiGeometry>
      </Placemark>
    </Document>
  </Document>
</kml>

我尝试使用以下代码：

主要

 public T DeserializeToObject<T>(string filepath) where T : class
        {
            System.Xml.Serialization.XmlSerializer xmlSerializer = new System.Xml.Serialization.XmlSerializer(typeof(T));

            using (StreamReader streamReader = new StreamReader(filepath))
            {
                return (T)xmlSerializer.Deserialize(streamReader);
            }
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            String pathKml = @"C:\PruebaKML4g.kml";

            List<Kml> elementsList = DeserializeToObject<List<Kml>>(pathKml);
        }

Kml.cs

 /*[XmlRoot(ElementName = "kml")] changed by Mike Clark suggestion*/ 
[XmlRoot(ElementName = "kml", Namespace = "http://www.opengis.net/kml/2.2")]
    public class Kml

    {
        public List<Polygon> polygons = new List<Polygon>();
    }

    public class Polygon
    {
        [XmlAttribute("outerBoundaryIs")]
        public String outerBoundaryIs { get; set; }

        [XmlAttribute("linearRing")]
        public String linearRing { get; set; }

        [XmlAttribute("coordinates")]
        public String coordinates { get; set; }
    }

但是，XML 文件中的 SimpleData 元素似乎干扰了我的解析，生成了以下错误

InvalidOperationException: xmlns='http://www.opengis.net/kml/2.2'> was not expected.

任何关于我的错误所在的线索将不胜感激。

Answer 1

经过所有这些转换步骤，也许 XML 文件格式不正确？或者可能是有这么多数据的内存错误？尝试使用低内存要求的 SAX 解析器解析文件，让它找到可能深埋在文件中的任何语法错误。你有安装 Python 吗？

python -c "import xml.sax;p=xml.sax.make_parser();p.parse(r'yourfile.xml')"

将 yourfile.xml 更改为 XML 文件的正确路径和文件名。

如果不打印任何内容，则文件在句法上是有效的。如果它打印错误，请尝试使用错误中的 line:column 信息来发现 XML.

中的错误

第 2 部分：

List<Kml> elementsList = DeserializeToObject<List<Kml>>(pathKml);

可能是错误的。 XML 文档可以有一个且只有一个根 <element>（在这种情况下，<kml>）所以我认为拥有一个 Kml 实例列表对解析器来说没有意义。试试这个：

Kml root = DeserializeToObject<Kml>(pathKml);

但与下一个问题相比，这是一个简单的问题，我认为您的 C# class 结构需要准确反映 XML 的层次结构。多边形在此层次结构下：

kml > Document > Document > Placemark > MultiGeometry

这意味着你需要像

这样的东西

class Kml {
  Document Document;
}
class Document {
  Document Document;
  Placemark Placemark;
}
class Placemark {
  Polygon[] MultiGeometry;
}
class Polygon {
  OuterBoundaryIs outerBoundaryIs;
}
class OuterBoundaryIs {
  LinearRing LinearRing;
}
class LinearRing {
  string coordinates;
}

那么你需要像

这样的东西

var polygons = kml.Document.Document.Placemark.MultiGeometry;
for(int i = 0; i < polygons.Length; i++) {
  var polygon = polygons[i];
  string coordinates = polygon.outerBoundaryIs.LinearRing.coordinates;
  // do something with coordinates
}

顺便说一句，对于这种类型的东西，一种更好的解析器是 XPath 解析器，它可以避免使用 C# classes 对 XML 结构进行建模。制作 XPath 查询需要一些实践和研究，但生成的代码更清晰，并且有一些经验是一项很好的技能。更多 XPath 参见：

https://docs.microsoft.com/en-us/dotnet/standard/data/xml/select-nodes-using-xpath-navigation

C# 将 XML 文件转换为多个多边形对象

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