C#中Dictionary<string, object>转类型遇InvalidCastException问题求助

问题原因 #

Newtonsoft.Json在反序列化无类型的Dictionary<string, object>时，会将JSON中的整数默认解析为long类型（而非int）。当你用(int)直接强制转换装箱后的long对象时，就会抛出System.InvalidCastException——因为装箱值的实际类型与目标类型不匹配。此外，ObservableCollection<LevelCardGroup>的强转也可能失败，因为反序列化返回的通常是List<LevelCardGroup>而非ObservableCollection。

解决方案 #

方案1：直接反序列化为GameStats（最优解） #

跳过Dictionary中转，直接将JSON字符串反序列化为GameStats对象，让Newtonsoft.Json自动处理类型映射，彻底避免手动转换的问题：

public async Task ReadGameFileInAsync(string gameVersion)
{
    string filePath = gameVersion == "bronze" ? BronzeGameSaveFilePath : SilverGameSaveFilePath;
    string jsonContent = await ReadFileInAsync(filePath);
    
    // 直接反序列化为GameStats实例
    var loadedStats = JsonConvert.DeserializeObject<GameStats>(jsonContent);
    
    // 同步属性到_GameStats
    _GameStats.CurrentGame = loadedStats.CurrentGame;
    _GameStats.CurrentWord = loadedStats.CurrentWord;
    _GameStats.Score = loadedStats.Score;
    _GameStats.BestScore = loadedStats.BestScore;
    _GameStats.Difficulty = loadedStats.Difficulty;
    _GameStats.IsNewGame = loadedStats.IsNewGame;
    _GameStats.IsContinue = loadedStats.IsContinue;
    _GameStats.IsUnlocked = loadedStats.IsUnlocked;
    _GameStats.GameVersion = loadedStats.GameVersion;
    
    // 转换List为ObservableCollection
    _GameStats.Cards.Clear();
    foreach (var cardGroup in loadedStats.Cards)
    {
        _GameStats.Cards.Add(cardGroup);
    }
}

注意：确保LevelCardGroup类有公共无参构造函数，且属性可被Newtonsoft.Json正确序列化/反序列化。

方案2：保留Dictionary中转，使用安全转换 #

如果必须使用Dictionary，替换直接强转为Convert.ToInt32()，它能安全处理装箱的long、int甚至字符串类型的数字：

public async Task ReadGameFileInAsync(string gameVersion)
{
    var gameSave = new Dictionary<string, object>();
    if (gameVersion == "bronze")
        gameSave = JsonConvert.DeserializeObject<Dictionary<string, object>>(await ReadFileInAsync(BronzeGameSaveFilePath));
    else if (gameVersion == "silver")
        gameSave = JsonConvert.DeserializeObject<Dictionary<string, object>>(await ReadFileInAsync(SilverGameSaveFilePath));

    // 用Convert.ToInt32替代直接强转
    _GameStats.CurrentGame = Convert.ToInt32(gameSave["CurrentGame"]);
    _GameStats.CurrentWord = Convert.ToInt32(gameSave["CurrentWord"]);
    _GameStats.Score = Convert.ToInt32(gameSave["Score"]);
    _GameStats.BestScore = Convert.ToInt32(gameSave["BestScore"]);
    _GameStats.Difficulty = Convert.ToInt32(gameSave["Difficulty"]);
    
    _GameStats.IsNewGame = (bool)gameSave["IsNewGame"];
    _GameStats.IsContinue = (bool)gameSave["IsContinue"];
    _GameStats.IsUnlocked = (bool)gameSave["IsUnlocked"];
    _GameStats.GameVersion = (string)gameSave["GameVersion"];
    
    // 转换List为ObservableCollection
    var cardList = gameSave["Cards"] as List<LevelCardGroup>;
    if (cardList != null)
    {
        _GameStats.Cards.Clear();
        foreach (var group in cardList)
        {
            _GameStats.Cards.Add(group);
        }
    }
}

额外优化：避免KeyNotFoundException #

建议在读取字典值时先检查键是否存在，防止因存档缺失字段导致崩溃：

if (gameSave.TryGetValue("CurrentGame", out object currentGameObj))
{
    _GameStats.CurrentGame = Convert.ToInt32(currentGameObj);
}
else
{
    // 使用默认值或处理缺失逻辑
    _GameStats.CurrentGame = 1;
}

内容的提问来源于stack exchange，提问作者ThisQRequiresASpecialist