C# xna windows phone中的文件I/O。。。。读写文本数据

我想增加玩家的分数并检查高分，以便将分数存储在文本文件中。我正在尝试下面的代码，但它抛出异常

异常：值不在预期范围内

public void storage()
{

    var appstorage = IsolatedStorageFile.GetUserStoreForApplication();
    String filename = "store.txt";
    using (var file = appstorage.OpenFile(filename, FileMode.OpenOrCreate,FileAccess.ReadWrite))
    {

        using (var writer = new StreamWriter(file))
        {
            writer.Write(score);
        }

        using(var reader=new StreamReader(file)) 
        {
            playerscore =reader.ReadLine();

        }


    }
}

---

我真的不确定是否支持windows phone，但在windows中我会这样做

using (var file = File.Open(filename, FileMode.OpenOrCreate, FileAccess.ReadWrite))
{
    using (var writer = new BinaryWriter(file))
    {
       writer.Write(score);
    }

    using (var reader = new BinaryReader(file))
    {
        playerscore = reader.ReadInt32();
     }
}

当然，如果你只能读写文本，这将是解决方案

using (var file = File.Open(filename, FileMode.OpenOrCreate,` FileAccess.ReadWrite))
{
    using (var writer = new StreamWriter(file))
    {
        writer.WriteLine(score.ToString());
    }

    using (var reader = new StreamReader(file))
    {
        playerscore = int.Parse(reader.ReadLine());

    }
}