数据加密之文件/流加密解密

  /// <summary>  
    /// 为EndCallback提供数据  
    /// </summary>  
    public class EndState
    {
        internal EndState(bool isCancel, object state)
        {
            IsCancel = isCancel;
            State = state;
        }

        /// <summary>  
        /// 是否取消退出的  
        /// </summary>  
        public bool IsCancel { get; private set; }

        /// <summary>  
        /// 获得传递的参数  
        /// </summary>  
        public object State { get; private set; }
    }


    /// <summary>  
    /// 为ProgressCallback提供数据  
    /// </summary>  
    public class ProgressState
    {
        internal ProgressState(long byteRead, long totalBytesLength, object state)
        {
            BytesRead = byteRead;
            TotalBytesLength = totalBytesLength;
            State = state;
        }

        /// <summary>  
        /// 获得已经计算完成的字节数  
        /// </summary>  
        public long BytesRead { get; private set; }

        /// <summary>  
        /// 获得总字节数  
        /// </summary>  
        public long TotalBytesLength { get; private set; }

        /// <summary>  
        /// 获得传递的参数  
        /// </summary>  
        public object State { get; private set; }
    }

测试代码：

//------下面为对文件/流加密解密的需要实例化的部分------  

        /// <summary>  
        /// 完成计算的回调  
        /// </summary>  
        public delegate void EndCallback(EndState endState);

        /// <summary>  
        /// 进行计算时的回调  
        /// </summary>  
        public delegate void ProgressCallback(ProgressState progressState);

        private bool _cancel; //取消计算  

        /// <summary>  
        /// 停止计算  
        /// </summary>  
        public void Stop()
        {
            _cancel = true;
        }
        public void DecryptData(Stream inStream, Stream outStream, SymmetricAlgorithm alg, ProgressCallback progressCallback, EndCallback endCallback, object state)
        {
            const int bufferSize = 100;
            _cancel = false;

            long bytesRead = 0L;
            long totalBytesLength = inStream.Length;
            var buffer = new byte[bufferSize];

            using (var encStream = new CryptoStream(inStream, alg.CreateDecryptor(), CryptoStreamMode.Read))
            {
                int num;
                do
                {
                    num = encStream.Read(buffer, 0, bufferSize);
                    outStream.Write(buffer, 0, num);
                    if (progressCallback == null) continue;
                    bytesRead += num;
                    progressCallback(new ProgressState(bytesRead, totalBytesLength, state)); //进度回调  
                } while (num > 0 && !_cancel);
                if (endCallback != null) endCallback(new EndState(_cancel, state)); //计算结束回调  
            }
        }

        public void DecryptData(string inFileName, string outFileName, SymmetricAlgorithm alg, ProgressCallback progressCallback, EndCallback endCallback, object state)
        {
            using (var infs = new FileStream(inFileName, FileMode.Open, FileAccess.Read, FileShare.Read))
            {
                using (var outfs = new FileStream(outFileName, FileMode.OpenOrCreate, FileAccess.Write, FileShare.Read))
                {
                    DecryptData(infs, outfs, alg, progressCallback, endCallback, state);
                }
            }
        }

参考：http://blog.csdn.net/oyi319/article/details/5836010