CryptoStream是否可以返回並且仍然可以正確處理所有內容？

Question

如果我有一個CryptoStream，我想傳遞給用戶，幼稚的做法是

public Stream GetDecryptedFileStream(string inputFile, byte[] key, byte[] iv) 
{ 
    var fsCrypt = new FileStream(inputFile, FileMode.Open, FileAccess.Read, FileShare.Read); 
    var rmCrypto = new RijndaelManaged(); 
    var transform = rmCrypto.CreateDecryptor(key, iv); 
    var cs = new CryptoStream(fsCrypt, transform, CryptoStreamMode.Read); 

    return cs; 
} 

我知道，當我處置CryptoStream底層FileStreamwill also be disposed。我遇到的問題是：我如何處理rmCrypto和transform？ RijndaelManaged和ICryptoTransform是一次性類，但處置流不會處理這兩個對象。

處理這種情況的正確方法是什麼？

Answer 1

我會考慮創建自己的包裝流的類，然後您可以管理這些處理。沿着這些線的東西（抱歉 - 不知道轉換對象的類型離開我的頭頂）。

public CryptoStreamWrapper : Stream, IDisposable 
{ 
    public CryptoStreamWrapper(CryptoStream stream, RijndaelManaged rmCrypto, IDisposable transform) 
    { 
     this.transform = transform; 
     this.rmCrypto = rmCrypto; 
     this.stream = stream; 
    } 

    public void Dispose() 
    { 
     this.transform.Dispose(); 
     this.rmCrypto.Dispose(); 
     this.stream.Dispose(); 
    } 
} 

Answer 2

伊恩打我的基本概念（go upvote him），但CryptoStream的本身是不密封的，因此是微不足道的做一個派生類包裝了需要處理的事情。

/// <summary> 
/// Creates a class that creates a <see cref="CryptoStream"/> and wraps the disposing action of all the associated objects 
/// </summary> 
class ReturnableCryptoStream : CryptoStream 
{ 
    private readonly ICryptoTransform _transform; 
    private readonly IDisposable _algorithm; 

    public ReturnableCryptoStream(Stream stream, ICryptoTransform transform, CryptoStreamMode mode) 
     : this(stream, transform, mode, null) 
    { 
    } 

    public ReturnableCryptoStream(Stream stream, ICryptoTransform transform, CryptoStreamMode mode, IDisposable algorithm) 
     : base(stream, transform, mode) 
    { 
     _transform = transform; 
     _algorithm = algorithm; 
    } 

    protected override void Dispose(bool disposing) 
    { 
     base.Dispose(disposing); 
     if (disposing) 
     { 
      if (_transform != null) 
       _transform.Dispose(); 

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

一樣使用

public Stream GetDecryptedFileStream(string inputFile, byte[] key, byte[] iv) 
{ 
    var fsCrypt = new FileStream(inputFile, FileMode.Open, FileAccess.Read, FileShare.Read); 
    var rmCrypto = new RijndaelManaged(); 
    var transform = rmCrypto.CreateDecryptor(key, iv); 
    var cs = new ReturnableCryptoStream(fsCrypt, transform, CryptoStreamMode.Read, rmCrypto); 

    return cs; 
}