我写一个加密程序。将一个文件加密写到另一个文件中。其中要两次写入流。 
byte[] data-〉CryptoStream cs； 
data[] data->FileStream fs； 

如果第一步是同步，第二步是异步。就没有问题，但是内存消耗太大，我想两次都用异步 
。 
这该如何控制呢？ 
代码如下：其中文件是否写完的条件是写入和读取的计数器相同。 


            public class CryStateObject 
            { 
                public byte[] buffer; 
                public MemoryStream ms;//内存流 
                public CryptoStream cs;//加密流 
            } 


        public void EncryptFile(string filename) 
        { 
            bProccessFile=true; 
            originFile=new FileStream("a.dat",FileMode.Open);//源文件 
            processFile=new FileStream("b.dat",FileMode.Create);//要加密的文件 

            CryStateObject cobject=new CryStateObject(); 
            cobject.ms=new MemoryStream(); 
            cobject.buffer=new byte[buffersize]; 
            byte[] byteTemp=new byte[Convert.ToInt32(buffersize*0.8)]; 
            this.proceed=0;//已处理的长度 
            int datalen=0;//一次读入的长度 
            recvCallCount=recvCallbackCount=0; 
            while(this.proceed<originFile.Length) 
            { 
                recvCallCount++; 
                datalen=originFile.Read(byteTemp,0,byteTemp.Length); 
                this.proceed+=datalen; 
                cobject.ms=new MemoryStream(); 

                transform = symm.CreateEncryptor(symm.Key,symm.IV); 
                cobject.cs = new CryptoStream(cobject.ms, transform, CryptoStr 
eamMode.Write); 
                 
                cobject.cs.Write(byteTemp, 0, datalen); 
                cobject.cs.FlushFinalBlock(); 
                byte[] data=cobject.ms.ToArray(); 

                string strLen=data.Length.ToString();//记录每次加密的字节数，解 
密时同样处理 
                byte[] byteLen=Encoding.ASCII.GetBytes(strLen+"\x10"); 
                processFile.Write(byteLen,0,byteLen.Length); 
                processFile.BeginWrite(data,0,data.Length,new AsyncCallback(En 
cryptFileWriteBack),processFile);                 
            } 
        } 

        private void EncryptFileWriteBack(IAsyncResult iar) 
        { 
            lock(this) 
            { 
                recvCallbackCount++;                 
                FileStream file=(FileStream)iar.AsyncState; 
                file.EndWrite(iar); 
                RaiseWriteEncryptFileEvent(originFile.Length.ToString(),(doubl 
e)this.proceed); 
                if(recvCallbackCount==recvCallCount)//加密结束 
                { 
                    this.originFile.Close(); 
                    this.processFile.Close(); 
                } 
            } 
        }