C#使用文件流FileStream和内存流MemoryStream操作底层字节数组byte[]

//创建d:\file.txt的FileStream对象
FileStream fstream = new FileStream(@"d:\file.txt", FileMode.OpenOrCreate);
byte[] bData = new byte[fstream.Length];
//设置流当前位置为文件开始位置
fstream.Seek(0, SeekOrigin.Begin);

//将文件的内容存到字节数组中（缓存）
fstream.Read(bData, 0, bData.Length);
string result = Encoding.UTF8.GetString(bData);
Console.WriteLine(result);
if (fstream != null)
{
    //清除此流的缓冲区，使得所有缓冲的数据都写入到文件中
    fstream.Flush();
    fstream.Close();
}

//1、显示成图片
MemoryStream mstream = new MemoryStream(bData);
Image img = Image.FromStream(mstream);

 //2、作为值存储到数据库
SqlCommand comm = new SqlCommand();
comm.Parameters.Add("images", SqlDbType.Image).Value = bData;

 //3、写入文件
File.WriteAllBytes("c:\aa.txt", bData);
FileStream fstream = new FileStream("c:\aa.txt");
fstream.Write(bData, 0, bData.Length);

int bufferSize = 5;
//创建d:\file.txt的FileStream对象
FileStream fstream = new FileStream(@"d:\file.txt", FileMode.OpenOrCreate, FileAccess.Read, FileShare.Read, bufferSize, false);//false表示同步读
byte[] bData = new byte[bufferSize];
//设置流当前位置为文件开始位置
fstream.Seek(0, SeekOrigin.Begin);
int bytesRead;
do
{
    //将文件的内容存到字节数组中（缓存）
    bytesRead = fstream.Read(bData, 0, bData.Length);
    string result = Encoding.UTF8.GetString(bData, 0, bytesRead);
    Console.WriteLine(result);
} while (bytesRead > 0);

if (fstream != null)
{
    //清除此流的缓冲区，使得所有缓冲的数据都写入到文件中
    fstream.Flush();
    fstream.Close();
}

ManualResetEvent mEvent = new ManualResetEvent(false);
int bufferSize = 5;
byte[] bData = new byte[bufferSize];
FileStream fstream = new FileStream(@"d:\file.txt", FileMode.OpenOrCreate, FileAccess.Read, FileShare.Read, bufferSize, true);//false表示异步读

AsyncCallback callback = null;
callback = (IAsyncResult ar) => 
  {
      int bytesRead = fstream.EndRead(ar);
      Console.WriteLine(Encoding.UTF8.GetString(bData, 0, bytesRead));
      if (bytesRead > 0)
      {
          fstream.BeginRead(bData, 0, bufferSize, callback, null);//继续读
      }
      else
      {
          fstream.Close();
          mEvent.Set();//读取完毕，发送信号
      }
  };

IAsyncResult async = fstream.BeginRead(bData, 0, bufferSize, callback, null);
mEvent.WaitOne(5000, false);
Console.WriteLine("读取完成");

//创建d:\file.txt的FileStream对象
FileStream fstream = new FileStream(@"d:\file.txt", FileMode.OpenOrCreate);
byte[] bData = Encoding.UTF8.GetBytes("test filestream");
//设置流当前位置为文件开始位置
fstream.Seek(0, SeekOrigin.Begin);

//将字节数组中的内容写入文件
fstream.Write(bData, 0, bData.Length);
if (fstream != null)
{
    //清除此流的缓冲区，使得所有缓冲的数据都写入到文件中
    fstream.Flush();
    fstream.Close();
}

int count;
UnicodeEncoding uniEncoding = new UnicodeEncoding();

//创建要写入流的数据 
byte[] firstString = uniEncoding.GetBytes("Invalid file path characters are: ");
byte[] secondString = uniEncoding.GetBytes(Path.GetInvalidPathChars());

using (MemoryStream memStream = new MemoryStream(100))
{
    // 将第一个字符串写入流.
    memStream.Write(firstString, 0, firstString.Length);

    // 将第二个字符串按字节写入流.
    count = 0;
    while (count < secondString.Length)
    {
        memStream.WriteByte(secondString[count++]);
    }

    // 将流属性写入控制台.
    Console.WriteLine("Capacity = {0}, Length = {1}, Position = {2}\n", memStream.Capacity.ToString(), memStream.Length.ToString(), memStream.Position.ToString());

    // 将位置设置为流的开始.
    memStream.Seek(0, SeekOrigin.Begin);

    // 从流中读取前20个字节.
    byte[] byteArray = new byte[memStream.Length];
    count = memStream.Read(byteArray, 0, 20);

    // 一个字节一个字节地读取剩下的字节.
    while (count < memStream.Length)
    {
        byteArray[count++] = Convert.ToByte(memStream.ReadByte());
    }

    // 将字节数组解码为char数组并将其写入控制台.
    char[] charArray = new char[uniEncoding.GetCharCount(byteArray, 0, count)];
    uniEncoding.GetDecoder().GetChars(byteArray, 0, count, charArray, 0);
    Console.WriteLine(charArray);
}

//将流中的数据复制到一个byte[]中，速度比GetBuffer（）稍慢，但不会将无用的空数据放入buffer中。 
byte[] byteArray = memStream.ToArray();

//把流中的Buffer的引用传递出来，速度较快，Buffer的大小有流的Capacity决定的，但会传无用的空数据。
byte[] byteArray = memStream.GetBuffer();