XmlSerializer.Deserialize() 似乎不起作用

Question

I'm able to successfully serialize and save data in XML UTF-8 format as far as I can tell but, I am not able to deserialize that very same data.

I've tried researching this problem but, nobody seems to have the same issue of just deserialization not working. That's what I believe to be the problem at least.

    public static class XMLManager
    {
        //Save Function
        public static void SaveItemsUTF(ItemDatabase itemDB)
        {
            XmlSerializer serializer = new XmlSerializer(typeof(ItemDatabase));
            string filename = Application.dataPath + "/StreamingFiles/XML/item_data.xml";
            Encoding encoding = Encoding.GetEncoding("UTF-8");

            using (StreamWriter stream = new StreamWriter(filename, false, encoding))
            {
                serializer.Serialize(stream, itemDB);
            }
        }

        //Load Function
        public static void LoadItems(ItemDatabase itemDB)
        {
            //Open an XML File
            if (File.Exists(Application.dataPath + "/StreamingFiles/XML/item_data.xml"))
            {
                XmlSerializer serializer = new XmlSerializer(typeof(ItemDatabase));
                FileStream stream = new FileStream(Application.dataPath + "/StreamingFiles/XML/item_data.xml", FileMode.Open);
                itemDB = serializer.Deserialize(stream) as ItemDatabase;
                stream.Close();
            }
            else
            {
                Debug.LogError("File not found!");
            }
        }

        //Delete Function
        public static void DeleteItems()
        {
            //Delete an XML File
            File.Delete(Application.dataPath + "/StreamingFiles/XML/item_data.xml");
        }
    }

    [System.Serializable]
    public class ItemEntry
    {
        public string ItemName;
        public SaveMaterial material;
        public int Value;
    }

    [System.Serializable]
    public class ItemDatabase
    {
        [XmlArray("CombatEquipment")]
        public List<ItemEntry> list = new List<ItemEntry>();
    }

    public enum SaveMaterial
    {
        Wood,
        Copper,
        Iron,
        Steel,
        Obsidian
    }

When I use the SaveItemsUTF method, it successfully produces a file with the test data in the correct format in the correct location which can be seen here: https://imgur.com/a/5PJMTRh

However, when I use the LoadItems method, nothing appears to happen. No errors or logs in the console. No data gets loaded. It appears to do nothing. I am officially stuck.

Answer 1

It is deserialized. You can put breakpoint and see that element in LoadItems is filled with correct data.

But now the issue is about the way value/reference types work in .NET. You cannot change the value (reassign reference, to which itemDB is pointint to in method; you can change data inside it though, but that's other topoic) from method, where it's used. Strictly speaking, " object is passed to methods by reference, but the reference itself is passed by value; if you really need to reassign reference in method, use modifiers for that ".

So either use ref/out modifiers (as pointed by BrettCaswell in comments section, out is preferred; it's the way to say "content is passed by reference and will be reassigned inside", while ref means "content is passed by reference and might be reassigned inside"):

public static void LoadItems(out ItemDatabase itemDB); // will work; but you'll call it as below, with out modifier: 
// XMLManager.LoadItems(out itemDBName);

or change to:

public static ItemDatabase LoadItems(); // also will work, but, of course, you'll need to  create ItemDatabase internally in LoadItems

.NET encapsulates TryParse approach to solve similar tasks of both parsing data and providing status for parse); here is example with integer (value type): https://docs.microsoft.com/en-us/dotnet/api/system.int32.tryparse?view=netframework-4.8

Answer 2

You can use generic type functions, it make your code reusable for other object types. I can not check my code, so maybe it can give some error.

static void Serialize<T>(T data, string path)
{
    FileStream fs = new FileStream(path, FileMode.Create);
    XmlSerializer serializer = new XmlSerializer(typeof(T));
    serializer.Serialize(fs, data);
    fs.Close();
}


static T Deserialize<T>(string path)
{
    FileStream fs = new FileStream(path, FileMode.Open);
    XmlSerializer xs = new XmlSerializer(typeof(T));
    T obj = (T)xs.Deserialize(fs);
    fs.Close();
    return obj;
}