2

我正在尝试将对象序列化为内存流，然后加密此流，然后将其写入文件。无法弄清楚出了什么问题，“解密”后内存流为空。

    public static async Task SerializeToFileEncrypt<T>(T o, StorageFile file)
    {
            DataContractSerializer dsc = new DataContractSerializer(typeof(T));                
            MemoryStream memoryStream = new MemoryStream();
            dsc.WriteObject(memoryStream, o);
            DataProtectionProvider provider = new DataProtectionProvider("Local=User");
            var raStream = await file.OpenAsync(FileAccessMode.ReadWrite);
            using(var filestream = raStream.GetOutputStreamAt(0))
            {
                await provider.ProtectStreamAsync(memoryStream.AsInputStream(), filestream);
                await filestream.FlushAsync();                        
            }
    }

    public static async Task<T> DeserializeFromFileDecrypt<T>(StorageFile file)
    {
        DataContractSerializer dsc = new DataContractSerializer(typeof(T));
        MemoryStream memoryStream = new MemoryStream();
        DataProtectionProvider provider = new DataProtectionProvider();
        await provider.UnprotectStreamAsync((await file.OpenStreamForReadAsync()).AsInputStream(), memoryStream.AsOutputStream());
        return (T) dsc.ReadObject(memoryStream);
    }
4

2 回答 2

3

MemoryStream完成写入后，您需要移至开头。否则没有什么可以读取的，因为你已经定位到最后了。

这应该有效：

public static async Task SerializeToFileEncrypt<T>(T o, StorageFile file)
{
        DataContractSerializer dsc = new DataContractSerializer(typeof(T));                
        MemoryStream memoryStream = new MemoryStream();
        dsc.WriteObject(memoryStream, o);
        memoryStream.Seek(0, SeekOrigin.Begin); // move to the beginning of the stream
        DataProtectionProvider provider = new DataProtectionProvider("Local=User");
        var raStream = await file.OpenAsync(FileAccessMode.ReadWrite);
        using(var filestream = raStream.GetOutputStreamAt(0))
        {
            await provider.ProtectStreamAsync(memoryStream.AsInputStream(), filestream);
            await filestream.FlushAsync();                        
        }
}

public static async Task<T> DeserializeFromFileDecrypt<T>(StorageFile file)
{
    DataContractSerializer dsc = new DataContractSerializer(typeof(T));
    MemoryStream memoryStream = new MemoryStream();
    DataProtectionProvider provider = new DataProtectionProvider();
    await provider.UnprotectStreamAsync((await file.OpenStreamForReadAsync()).AsInputStream(), memoryStream.AsOutputStream());
    memoryStream.Seek(0, SeekOrigin.Begin); // move to the beginning of the stream
    return (T) dsc.ReadObject(memoryStream);
}
于 2012-04-22T16:07:46.373 回答
0

除了最后发布的答案之外，您需要将 raStream 包装在 using 语句中，因为它是一个 IDisposable 对象。否则，如果某些代码稍后尝试再次打开该文件，它将因访问被拒绝而失败，因为该文件仍由随机访问流打开。

public static async Task SerializeToFileEncrypt<T>(T o, StorageFile file)
        {
            DataContractSerializer dsc = new DataContractSerializer(typeof(T));
            MemoryStream memoryStream = new MemoryStream();
            dsc.WriteObject(memoryStream, o);
            memoryStream.Seek(0, SeekOrigin.Begin); // move to the beginning of the stream
            DataProtectionProvider provider = new DataProtectionProvider("Local=User");
            using (var raStream = await file.OpenAsync(FileAccessMode.ReadWrite))
            {
                using (var filestream = raStream.GetOutputStreamAt(0))
                {
                    await provider.ProtectStreamAsync(memoryStream.AsInputStream(), filestream);
                    await filestream.FlushAsync();
                }
            }
        }
于 2013-11-14T15:47:20.407 回答