Serialize an EditorWindow

Hello,

I am looking for a solution to serialize Action. This is a tutorial I found:
https://schemingdeveloper.com/2014/12/04/serializing-delegates-unity/
I am following the instruction above and then I met some problem.
This is the class which contains an Action:

Code (CSharp):

1. [Serializable]
2. public class ConnectionPoint: ISerializationCallbackReceiver
3. {
4.     public byte[] dataOnClickCo;
5.     public Rect rect;
6.  
7.     public ConnectionPointType type;
8.  
9.     public TreeNode node;
10.  
11.     public GUIStyle style;
12.  
13.     public Action<ConnectionPoint> OnClickConnectionPoint;
14. ...(Some Methods)
15.  
16.     public void OnBeforeSerialize() {
17.         using (var stream = new MemoryStream()) {
18.             //Write to a memory stream
19.             (new BinaryFormatter()).Serialize(stream, OnClickConnectionPoint);
20.             stream.Flush();
21.             //Store the information to a byte array
22.             dataOnClickCo = stream.ToArray();
23.         }
24.      
25.     }
26.  
27.     public void OnAfterDeserialize()
28.     {
29.         using (var stream = new MemoryStream(dataOnClickCo)) {
30.             OnClickConnectionPoint = (Action<ConnectionPoint>)(new BinaryFormatter()).Deserialize(stream);
31.         }
32.     }
33. }
34.  

And the action is from my EditorWindow class:

[Serializable]

Code (CSharp):

1. public class NodeBasedEditor : EditorWindow{
2.  
3. ...
4.  
5.     public void OnClickConnectPoint(ConnectionPoint inPoint)
6.     {
7.         selectedInPoint = inPoint;
8.  
9.         if (selectedOutPoint != null)
10.         {
11.             if (selectedOutPoint.node != selectedInPoint.node)
12.             {
13.                 CreateConnection();
14.                 ClearConnectionSelection();
15.             }
16.             else
17.             {
18.                 ClearConnectionSelection();
19.             }
20.         }
21.     }
22. }
23.  

Then I got the following error:
SerializationException: Type UnityEditor.EditorWindow in assembly UnityEditor, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null is not marked as serializable.

And I found the OnBeforeSerialize() is called automatically for some reason?