How to save a list of MonoBehaviours in a binary file

I have a code that saves data in the data file are saved without any problem.But I also tried to save an array but the array was not saved and I get an error.I keep the data (and also the array) in BinaryFormatter.The error indicates the line bf.Serialize (file, data) before closing the file in the save function.

the code

 public class SaveLoadScript : MonoBehaviour
 {
     public int allMoneyOfplayer, allXpOfPlayer, laval, maxXp, howMuchUpMaxXp;
     public float highTime;
     public List<GunScript> gun = new List<GunScript>();
     public void Start()
     {
         Save();
     }
     public void Update()
     {
 
     }
     public void Save()
     {
         BinaryFormatter bf = new BinaryFormatter();
         FileStream file = File.Create(Application.persistentDataPath + "/saveG.file");
         PlayerData data = new PlayerData();
         data.money = allMoneyOfplayer;
         data.xp = allXpOfPlayer;
         if (highTime > data.time)
             data.time = highTime;
         data.laval = laval;
         data.maxXp = maxXp;
         data.howMuchUpMaxXp = howMuchUpMaxXp;
         for (int i = 0; i < gun.Count; i++)
             data.gun.Add(gun[i]);
         bf.Serialize(file, data);
         file.Close();
     }
     public void Load()
     {
         if (File.Exists(Application.persistentDataPath + "/saveG.file"))
         {
             BinaryFormatter bf = new BinaryFormatter();
             FileStream file = File.Open(Application.persistentDataPath + "/saveG.file", FileMode.Open);
             PlayerData data = (PlayerData)bf.Deserialize(file);
             allMoneyOfplayer = data.money;
             allXpOfPlayer = data.xp;
             highTime = data.time;
             laval = data.laval;
             maxXp = data.maxXp;
             howMuchUpMaxXp = data.howMuchUpMaxXp;
             file.Close();
         }
     }
 }
 [System.Serializable]
 class PlayerData
 {
     public int money;
     public int xp;
     public float time;
     public int laval;
     public int maxXp;
     public int howMuchUpMaxXp;
     public List<GunScript> gun = new List<GunScript>();
 }

the error

 SerializationException: Type 'GunScript' in Assembly 'Assembly-CSharp, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null' is not marked as serializable.
 System.Runtime.Serialization.FormatterServices.InternalGetSerializableMembers (System.RuntimeType type) (at <fb001e01371b4adca20013e0ac763896>:0)
 System.Runtime.Serialization.FormatterServices+<>c__DisplayClass9_0.<GetSerializableMembers>b__0 (System.Runtime.Serialization.MemberHolder _) (at <fb001e01371b4adca20013e0ac763896>:0)
 System.Collections.Concurrent.ConcurrentDictionary`2[TKey,TValue].GetOrAdd (TKey key, System.Func`2[T,TResult] valueFactory) (at <fb001e01371b4adca20013e0ac763896>:0)
 System.Runtime.Serialization.FormatterServices.GetSerializableMembers (System.Type type, System.Runtime.Serialization.StreamingContext context) (at <fb001e01371b4adca20013e0ac763896>:0)
 System.Runtime.Serialization.Formatters.Binary.WriteObjectInfo.InitMemberInfo () (at <fb001e01371b4adca20013e0ac763896>:0)
 System.Runtime.Serialization.Formatters.Binary.WriteObjectInfo.InitSerialize (System.Type objectType, System.Runtime.Serialization.ISurrogateSelector surrogateSelector, System.Runtime.Serialization.StreamingContext context, System.Runtime.Serialization.Formatters.Binary.SerObjectInfoInit serObjectInfoInit, System.Runtime.Serialization.IFormatterConverter converter, System.Runtime.Serialization.SerializationBinder binder) (at <fb001e01371b4adca20013e0ac763896>:0)
 System.Runtime.Serialization.Formatters.Binary.WriteObjectInfo.Serialize (System.Type objectType, System.Runtime.Serialization.ISurrogateSelector surrogateSelector, System.Runtime.Serialization.StreamingContext context, System.Runtime.Serialization.Formatters.Binary.SerObjectInfoInit serObjectInfoInit, System.Runtime.Serialization.IFormatterConverter converter, System.Runtime.Serialization.SerializationBinder binder) (at <fb001e01371b4adca20013e0ac763896>:0)
 System.Runtime.Serialization.Formatters.Binary.ObjectWriter.WriteArray (System.Runtime.Serialization.Formatters.Binary.WriteObjectInfo objectInfo, System.Runtime.Serialization.Formatters.Binary.NameInfo memberNameInfo, System.Runtime.Serialization.Formatters.Binary.WriteObjectInfo memberObjectInfo) (at <fb001e01371b4adca20013e0ac763896>:0)
 System.Runtime.Serialization.Formatters.Binary.ObjectWriter.Write (System.Runtime.Serialization.Formatters.Binary.WriteObjectInfo objectInfo, System.Runtime.Serialization.Formatters.Binary.NameInfo memberNameInfo, System.Runtime.Serialization.Formatters.Binary.NameInfo typeNameInfo) (at <fb001e01371b4adca20013e0ac763896>:0)
 System.Runtime.Serialization.Formatters.Binary.ObjectWriter.Serialize (System.Object graph, System.Runtime.Remoting.Messaging.Header[] inHeaders, System.Runtime.Serialization.Formatters.Binary.__BinaryWriter serWriter, System.Boolean fCheck) (at <fb001e01371b4adca20013e0ac763896>:0)
 System.Runtime.Serialization.Formatters.Binary.BinaryFormatter.Serialize (System.IO.Stream serializationStream, System.Object graph, System.Runtime.Remoting.Messaging.Header[] headers, System.Boolean fCheck) (at <fb001e01371b4adca20013e0ac763896>:0)
 System.Runtime.Serialization.Formatters.Binary.BinaryFormatter.Serialize (System.IO.Stream serializationStream, System.Object graph, System.Runtime.Remoting.Messaging.Header[] headers) (at <fb001e01371b4adca20013e0ac763896>:0)
 System.Runtime.Serialization.Formatters.Binary.BinaryFormatter.Serialize (System.IO.Stream serializationStream, System.Object graph) (at <fb001e01371b4adca20013e0ac763896>:0)

Thanks for the help