在 XNA 上读取 XML 文件

嗨，我无法理解此错误

我想阅读这个 XML 文件：

<?xml version="1.0" encoding="utf-8"?>
<XnaContent>
  <Asset Type="ReadXML.Nod[]">
    <Item>
      <coneccion>
        <Item>
          <price>53.6003723</price>
          <startNode>
            <coneccion />
            <position>347 0 228</position>
          </startNode>
          <endNode>
            <coneccion />
            <position>334 0 176</position>
          </endNode>
        </Item>
      </coneccion>
      <position>347 0 228</position>
    </Item>
    <Item>
      <coneccion>
        <Item>
          <price>54.74486</price>
          <startNode>
            <coneccion />
            <position>334 0 176</position>
          </startNode>
          <endNode>
            <coneccion />
            <position>280 0 167</position>
          </endNode>
        </Item>
        <Item>
          <price>53.6003723</price>
          <startNode>
            <coneccion />
            <position>334 0 176</position>
          </startNode>
          <endNode>
            <coneccion />
            <position>347 0 228</position>
          </endNode>
        </Item>
      </coneccion>
      <position>334 0 176</position>
    </Item>
  </Asset>
</XnaContent>

我有这门课来阅读：

public class Nod
{
    public List<Coneccion> coneccion;
    public Vector3 position;
    public Nodo(Vector3 p)
    {
        position = p;
        coneccion = new List<Coneccion>();
    }
}

和

public class Coneccion
{
    public float price;
    public Nodo startNode;
    public Nodo endNode;
    public Coneccion(Nod c, Nod f, float cost)
    {
        startNode = c;
        endNode = f;
        price = cost;
    }
}

这些类模拟图形。

我必须读取这些名为 level 的 xml 文件.xml我使用这些函数进行读取

Nod[] graph1 = Content.Load<Nod[]>("level.xml");

但是我运行项目并打印下一个错误：

Error   1   Building content threw InvalidOperationException: Cannot deserialize type ReadXML.Nod because it does not have a parameterless constructor.
en Microsoft.Xna.Framework.Content.Pipeline.Serialization.Intermediate.ReflectiveSerializer.Deserialize(IntermediateReader input, ContentSerializerAttribute format, Object existingInstance)
en Microsoft.Xna.Framework.Content.Pipeline.Serialization.Intermediate.IntermediateReader.ReadRawObjectInternal[T](ContentSerializerAttribute format, ContentTypeSerializer typeSerializer, Object existingInstance)
en Microsoft.Xna.Framework.Content.Pipeline.Serialization.Intermediate.IntermediateReader.ReadObjectInternal[T](ContentSerializerAttribute format, ContentTypeSerializer typeSerializer, Object existingInstance)
en Microsoft.Xna.Framework.Content.Pipeline.Serialization.Intermediate.CollectionHelper.Deserialize(IntermediateReader input, ContentSerializerAttribute format, Object collection)
en Microsoft.Xna.Framework.Content.Pipeline.Serialization.Intermediate.ArraySerializer`1.Deserialize(IntermediateReader input, ContentSerializerAttribute format, T[] existingInstance)
en Microsoft.Xna.Framework.Content.Pipeline.Serialization.Intermediate.ContentTypeSerializer`1.Deserialize(IntermediateReader input, ContentSerializerAttribute format, Object existingInstance)
en Microsoft.Xna.Framework.Content.Pipeline.Serialization.Intermediate.IntermediateReader.ReadRawObjectInternal[T](ContentSerializerAttribute format, ContentTypeSerializer typeSerializer, Object existingInstance)
en Microsoft.Xna.Framework.Content.Pipeline.Serialization.Intermediate.IntermediateReader.ReadObjectInternal[T](ContentSerializerAttribute format, ContentTypeSerializer typeSerializer, Object existingInstance)
en Microsoft.Xna.Framework.Content.Pipeline.Serialization.Intermediate.IntermediateReader.ReadObject[T](ContentSerializerAttribute format)
en Microsoft.Xna.Framework.Content.Pipeline.Serialization.Intermediate.IntermediateSerializer.Deserialize[T](XmlReader input, String referenceRelocationPath)
en Microsoft.Xna.Framework.Content.Pipeline.XmlImporter.Import(String filename, ContentImporterContext context)
en Microsoft.Xna.Framework.Content.Pipeline.ContentImporter`1.Microsoft.Xna.Framework.Content.Pipeline.IContentImporter.Import(String filename, ContentImporterContext context)
en Microsoft.Xna.Framework.Content.Pipeline.BuildCoordinator.ImportAssetDirectly(BuildItem item, String importerName)
en Microsoft.Xna.Framework.Content.Pipeline.BuildCoordinator.ImportAsset(BuildItem item)
en Microsoft.Xna.Framework.Content.Pipeline.BuildCoordinator.BuildAssetWorker(BuildItem item)
en Microsoft.Xna.Framework.Content.Pipeline.BuildCoordinator.BuildAsset(BuildItem item)
en Microsoft.Xna.Framework.Content.Pipeline.BuildCoordinator.RunTheBuild()
en Microsoft.Xna.Framework.Content.Pipeline.Tasks.BuildContent.RemoteProxy.RunTheBuild(BuildCoordinatorSettings settings, TimestampCache timestampCache, ITaskItem[] sourceAssets, String[]& outputContent, String[]& rebuiltContent, String[]& intermediates, Dictionary`2& dependencyTimestamps, KeyValuePair`2[]& warnings)  C:'Downloads'Bomber-O-Man (Entrega 2)'IAJMovimiento'IAJMovimiento'IAJMovimientoContent'level.xml    IAJMovimiento

请帮忙

public Nodo()
{
    position = Vector3.Zero;
    coneccion = new List<Coneccion>();
}