CryptoStream可以让基流保持打开状态吗？

Question

我创建了一个MemoryStream，将它传递给CryptoStream进行写入。我想让CryptoStream加密，并让MemoryStream打开，让我读入其他内容。但是一旦处理完CryptoStream，它也会处理掉MemoryStream。

CryptoStream能以某种方式让基本MemoryStream保持打开状态吗？

using (MemoryStream scratch = new MemoryStream())
{
    using (AesManaged aes = new AesManaged())
    {
        // <snip>
        // Set some aes parameters, including Key, IV, etc.
        // </snip>
        ICryptoTransform encryptor = aes.CreateEncryptor();
        using (CryptoStream myCryptoStream = new CryptoStream(scratch, encryptor, CryptoStreamMode.Write))
        {
            myCryptoStream.Write(someByteArray, 0, someByteArray.Length);
        }
    }
    // Here, I'm still within the MemoryStream block, so I expect
    // MemoryStream to still be usable.
    scratch.Position = 0;    // Throws ObjectDisposedException
    byte[] scratchBytes = new byte[scratch.Length];
    scratch.Read(scratchBytes,0,scratchBytes.Length);
    return Convert.ToBase64String(scratchBytes);
}

Answer 1

您可以，但不能使用using语句。您将需要手动管理对象的处置，还需要调用FlushFinialBlock()以确保在对其进行操作之前所有数据都已写出到底层流中。

一旦您完成了对流的处理，您就可以在最后的finally块中处理您等待的所有资源。

MemoryStream scratch = null;
AesManaged aes = null;
CryptoStream myCryptoStream = null;
try
{
    scratch = new MemoryStream();
    aes = new AesManaged();

    // <snip>
    // Set some aes parameters, including Key, IV, etc.
    // </snip>
    ICryptoTransform encryptor = aes.CreateEncryptor();
    myCryptoStream = new CryptoStream(scratch, encryptor, CryptoStreamMode.Write);
    myCryptoStream.Write(someByteArray, 0, someByteArray.Length);

    //Flush the data out so it is fully written to the underlying stream.
    myCryptoStream.FlushFinalBlock();

    scratch.Position = 0; 
    byte[] scratchBytes = new byte[scratch.Length];
    scratch.Read(scratchBytes,0,scratchBytes.Length);
    return Convert.ToBase64String(scratchBytes);
}
finally
{
    //Dispose all of the disposeable objects we created in reverse order.

    if(myCryptoStream != null)
        myCryptoStream.Dispose();

    if(aes != null)
        aes.Dispose();

    if(scratch != null)
        scratch.Dispose();
}

Answer 2

从.NET 4.7.2开始，有了第二个构造函数，它添加了一个名为leaveOpen的布尔参数。如果设置为true，则CryptoStream的dispose方法将不会调用基础流上的dispose。

Additionally，另一个不带leaveOpen参数的构造函数只是将参数转发给leaveOpen设置为false的新构造函数。

MSDN

CryptoStream.Dispose(bool disposing)

Answer 3

作为第二种解决方案，您可以创建一个WrapperStream对象，该对象简单地传递除Dispose / Close之外的所有调用。在内存流周围做一个包装器，将包装器递给加密流，现在关闭加密流并不会接触到内存流。