Deserializing problem at runtime, InvalidCastException

Question

I was just messing around with serialization, when a strange error was popping up, only at runtime though. It says:

InvalidCastException: Cannot cast from source type to destination type. MyScript.Load ()

The adressed C# script (MyScript) contains this code:

     public static int highscore = 0;        //saved Highscore
     public static int collectedPoints = 0;    //Points collected on this account
     public static int lifetimeScore = 0;    //count of all points ever collected
 
     public static void Load()
     {
         if(File.Exists(Application.persistentDataPath + "/saveFiles.xyz"))
         {
             BinaryFormatter bf = new BinaryFormatter();
             FileStream file = File.Open(Application.persistentDataPath + "/saveFiles.xyz", FileMode.Open);
             SaveValues.highscore = (int)bf.Deserialize(file);
             SaveValues.collectedPoints = (int)bf.Deserialize(file);
             SaveValues.lifetimeScore = (int)bf.Deserialize(file);
             file.Close();
         }
     }
 
     public static void Save()
     {
         BinaryFormatter bf = new BinaryFormatter();
         FileStream file = File.Create (Application.persistentDataPath + "/saveFiles.xyz");
         bf.Serialize(file, SaveValues.highscore);
         bf.Serialize(file, SaveValues.collectedPoints);
         bf.Serialize (file, SaveValues.lifetimeScore);
         file.Close();
     }
 
     public static void Reset()
     {
         if (File.Exists (Application.persistentDataPath + "/saveFile.xyz"))
         {
             File.Delete (Application.persistentDataPath + "/saveFile.xyz");
             Application.LoadLevel(0);
         }
     }

SavedValues is the class containing these variables. I think the error is pointing towards the "SavedValues.lifetimeScore"-line in the Load()-function. What am i missing?

Thanks in advance.

Answer 1

Deserialize will deserialize an object graph from the given stream. It isn't ment to be used several times in a row. You should serialize one thing and that's what you will get back when you deserialize the stream. Usually you would use a data class like this one:

 [System.Serializable]
 public class SaveData
 {
     public int highscore = 0;
     public int collectedPoints = 0;
     public int lifetimeScore = 0;
 }

You can either create a temporary instance of that class, assign your values to the fields and then serialize it, or directly replace your static variables with a single variables to an instance of that SaveData class.

 public static SaveData data = new SaveData();

That way you always store the data directly into the instance. To access a value you would need to use

 MyScript.data.highscore = 42;
 // instead of
 MyScript.highscore = 42;

Now you can simply serialize and deserialize your SaveData class. When you deserialize it you will simple replace the current instance with the deserialized version:

 data = (SaveData)bf.Deserialize(file);

Deserializing problem at runtime, InvalidCastException

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