I create a MemoryStream
, pass it to CryptoStream
for writing. I want the CryptoStream
to encrypt, and leave the MemoryStream
open for me to then read into something else. But as soon as CryptoStream
is disposed, it disposes of MemoryStream
too.
Can CryptoStream
leave the base MemoryStream
open somehow?
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);
}
You can but you will not be able to use using statements. You will need to manually manage the disposing of the object and you will also need to call FlushFinialBlock()
to make sure all the data was written out to the underlying stream before working on it.
Once all you are done working with the stream you can then dispose all of the resources you where waiting on in the finally block at the end.
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();
}