XMLのシリアライズで例外が出る

Question

Unityでxmlにデータを保存するためにこんな感じにコードを書きました。

 /// <summary>
/// 保存
/// </summary>
/// <param name="path">xmlファイルの場所</param>
/// <param name="obj">シリアライズするオブジェクト</param>
public static void Save(string path, System.Object obj)
{
    Type type = obj.GetType();
    XmlSerializer ser = new XmlSerializer(type);
    StreamWriter sw = new StreamWriter(path, false, Encoding.UTF8);

    ser.Serialize(sw, obj);
    sw.Close();
 }

こうやってSave()を呼び出しました。

        string path = Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData) + "\Roaming\qqqq";
        var task1 = new Task(() => SavedataManager.Save( path + "Player.xml", player));
        task1.Start();
        task1.Wait();

そして呼び出すと

InvalidOperationException: To be XML serializable, types which inherit from IEnumerable must have an implementation of Add(System.Object) at all levels of their inheritance hierarchy. UnityEngine.Transform does not implement Add(System.Object).
System.Xml.Serialization.TypeScope.GetEnumeratorElementType (System.Type type, System.Xml.Serialization.TypeFlags& flags) (at <7fd195060d8c41448694ab221d3b56ca>:0)
System.Xml.Serialization.TypeScope.ImportTypeDesc (System.Type type, System.Reflection.MemberInfo memberInfo, System.Boolean directReference) (at <7fd195060d8c41448694ab221d3b56ca>:0)
System.Xml.Serialization.TypeScope.GetTypeDesc (System.Type type, System.Reflection.MemberInfo source, System.Boolean directReference, System.Boolean throwOnError) (at <7fd195060d8c41448694ab221d3b56ca>:0)
System.Xml.Serialization.StructModel.GetPropertyModel (System.Reflection.PropertyInfo propertyInfo) (at <7fd195060d8c41448694ab221d3b56ca>:0)
System.Xml.Serialization.StructModel.GetFieldModel (System.Reflection.MemberInfo memberInfo) (at <7fd195060d8c41448694ab221d3b56ca>:0)
System.Xml.Serialization.XmlReflectionImporter.InitializeStructMembers (System.Xml.Serialization.StructMapping mapping, System.Xml.Serialization.StructModel model, System.Boolean openModel, System.String typeName, System.Xml.Serialization.RecursionLimiter limiter) (at <7fd195060d8c41448694ab221d3b56ca>:0)
System.Xml.Serialization.XmlReflectionImporter.ImportStructLikeMapping (System.Xml.Serialization.StructModel model, System.String ns, System.Boolean openModel, System.Xml.Serialization.XmlAttributes a, System.Xml.Serialization.RecursionLimiter limiter) (at <7fd195060d8c41448694ab221d3b56ca>:0)
System.Xml.Serialization.XmlReflectionImporter.InitializeStructMembers (System.Xml.Serialization.StructMapping mapping, System.Xml.Serialization.StructModel model, System.Boolean openModel, System.String typeName, System.Xml.Serialization.RecursionLimiter limiter) (at <7fd195060d8c41448694ab221d3b56ca>:0)
System.Xml.Serialization.XmlReflectionImporter.ImportStructLikeMapping (System.Xml.Serialization.StructModel model, System.String ns, System.Boolean openModel, System.Xml.Serialization.XmlAttributes a, System.Xml.Serialization.RecursionLimiter limiter) (at <7fd195060d8c41448694ab221d3b56ca>:0)
System.Xml.Serialization.XmlReflectionImporter.InitializeStructMembers (System.Xml.Serialization.StructMapping mapping, System.Xml.Serialization.StructModel model, System.Boolean openModel, System.String typeName, System.Xml.Serialization.RecursionLimiter limiter) (at <7fd195060d8c41448694ab221d3b56ca>:0)
System.Xml.Serialization.XmlReflectionImporter.ImportStructLikeMapping (System.Xml.Serialization.StructModel model, System.String ns, System.Boolean openModel, System.Xml.Serialization.XmlAttributes a, System.Xml.Serialization.RecursionLimiter limiter) (at <7fd195060d8c41448694ab221d3b56ca>:0)
System.Xml.Serialization.XmlReflectionImporter.InitializeStructMembers (System.Xml.Serialization.StructMapping mapping, System.Xml.Serialization.StructModel model, System.Boolean openModel, System.String typeName, System.Xml.Serialization.RecursionLimiter limiter) (at <7fd195060d8c41448694ab221d3b56ca>:0)
System.Xml.Serialization.XmlReflectionImporter.ImportStructLikeMapping (System.Xml.Serialization.StructModel model, System.String ns, System.Boolean openModel, System.Xml.Serialization.XmlAttributes a, System.Xml.Serialization.RecursionLimiter limiter) (at <7fd195060d8c41448694ab221d3b56ca>:0)
System.Xml.Serialization.XmlReflectionImporter.ImportTypeMapping (System.Xml.Serialization.TypeModel model, System.String ns, System.Xml.Serialization.XmlReflectionImporter+ImportContext context, System.String dataType, System.Xml.Serialization.XmlAttributes a, System.Boolean repeats, System.Boolean openModel, System.Xml.Serialization.RecursionLimiter limiter) (at <7fd195060d8c41448694ab221d3b56ca>:0)
Rethrow as InvalidOperationException: There was an error reflecting type 'Player'.
System.Xml.Serialization.XmlReflectionImporter.ImportTypeMapping (System.Xml.Serialization.TypeModel model, System.String ns, System.Xml.Serialization.XmlReflectionImporter+ImportContext context, System.String dataType, System.Xml.Serialization.XmlAttributes a, System.Boolean repeats, System.Boolean openModel, System.Xml.Serialization.RecursionLimiter limiter) (at <7fd195060d8c41448694ab221d3b56ca>:0)
System.Xml.Serialization.XmlReflectionImporter.ImportTypeMapping (System.Xml.Serialization.TypeModel model, System.String ns, System.Xml.Serialization.XmlReflectionImporter+ImportContext context, System.String dataType, System.Xml.Serialization.XmlAttributes a, System.Xml.Serialization.RecursionLimiter limiter) (at <7fd195060d8c41448694ab221d3b56ca>:0)
System.Xml.Serialization.XmlReflectionImporter.ImportElement (System.Xml.Serialization.TypeModel model, System.Xml.Serialization.XmlRootAttribute root, System.String defaultNamespace, System.Xml.Serialization.RecursionLimiter limiter) (at <7fd195060d8c41448694ab221d3b56ca>:0)
System.Xml.Serialization.XmlReflectionImporter.ImportTypeMapping (System.Type type, System.Xml.Serialization.XmlRootAttribute root, System.String defaultNamespace) (at <7fd195060d8c41448694ab221d3b56ca>:0)
System.Xml.Serialization.XmlSerializer..ctor (System.Type type, System.String defaultNamespace) (at <7fd195060d8c41448694ab221d3b56ca>:0)
System.Xml.Serialization.XmlSerializer..ctor (System.Type type) (at <7fd195060d8c41448694ab221d3b56ca>:0)
SavedataManager.Save (System.String path, System.Object obj) (at Assets/AST/SavedataManager/script/SavedataManager.cs:17)
GameController.<Save>m__0 () (at Assets/script/GameController.cs:47)
System.Threading.Tasks.Task.InnerInvoke () (at <e1a80661d61443feb3dbdaac88eeb776>:0)
System.Threading.Tasks.Task.Execute () (at <e1a80661d61443feb3dbdaac88eeb776>:0)
Rethrow as AggregateException: One or more errors occurred.
System.Threading.Tasks.Task.ThrowIfExceptional (System.Boolean includeTaskCanceledExceptions) (at <e1a80661d61443feb3dbdaac88eeb776>:0)
System.Threading.Tasks.Task.Wait (System.Int32 millisecondsTimeout, System.Threading.CancellationToken cancellationToken) (at <e1a80661d61443feb3dbdaac88eeb776>:0)
System.Threading.Tasks.Task.Wait () (at <e1a80661d61443feb3dbdaac88eeb776>:0)
GameController.Save (System.Boolean isExit) (at Assets/script/GameController.cs:49)
UnityEngine.Events.InvokableCall`1[T1].Invoke (T1 args0) (at C:/buildslave/unity/build/Runtime/Export/UnityEvent.cs:207)
UnityEngine.Events.CachedInvokableCall`1[T].Invoke (System.Object[] args) (at C:/buildslave/unity/build/Runtime/Export/UnityEvent.cs:345)
UnityEngine.Events.UnityEvent.Invoke () (at C:/buildslave/unity/build/Runtime/Export/UnityEvent_0.cs:70)
UnityEngine.UI.Button.Press () (at C:/buildslave/unity/build/Extensions/guisystem/UnityEngine.UI/UI/Core/Button.cs:36)
UnityEngine.UI.Button.OnPointerClick (UnityEngine.EventSystems.PointerEventData eventData) (at C:/buildslave/unity/build/Extensions/guisystem/UnityEngine.UI/UI/Core/Button.cs:45)
UnityEngine.EventSystems.ExecuteEvents.Execute (UnityEngine.EventSystems.IPointerClickHandler handler, UnityEngine.EventSystems.BaseEventData eventData) (at C:/buildslave/unity/build/Extensions/guisystem/UnityEngine.UI/EventSystem/ExecuteEvents.cs:50)
UnityEngine.EventSystems.ExecuteEvents.Execute[T] (UnityEngine.GameObject target, UnityEngine.EventSystems.BaseEventData eventData, UnityEngine.EventSystems.ExecuteEvents+EventFunction`1[T1] functor) (at C:/buildslave/unity/build/Extensions/guisystem/UnityEngine.UI/EventSystem/ExecuteEvents.cs:261)
UnityEngine.EventSystems.EventSystem.Update()

例外の原因、アドバイスなどをしていただけたら助かります。

Answer 1

Unityは詳しくないので、外しているかも知れませんが、、、

var task1 = new Task(() => SavedataManager.Save( path + "Player.xml", player));

player というオブジェクトを シリアライズしているという事ですね。
このオブジェクトの内部に、Unityのオブジェクトを含んでいないでしょうか?
そこでエラーを出しているように見えます。
シリアライズ対象としたいデータのみで構成されたオブジェクト(クラス)を作成し、それを指定してシリアライズすべきと考えます。

Answer 2

XmlSerializerは、シリアライズするオブジェクトのクラスが、引数のないコンストラクタがある、シリアライズ対象のクラス変数はpropertyでなければならない、などなどの制約があったと思いますんでそこらへん確認してみては。

オブジェクトの内容をXMLファイルに保存（シリアル化）する

この方法によりXMLファイルに書き込まれるメンバは、パブリックメンバであるフィールドとプロパティだけです。さらに、読み込み、あるいは書き込みしか許可されていないプロパティは、パブリックメンバであっても書き込まれません。また、シリアル化するオブジェクトのクラスには、規定のコンストラクタ（パラメータを持たないコンストラクタ）が必要です。