如何在.net中将一个流的内容写入另一个流？

using System;
using System.IO;

public static void CopyStream(Stream inputStream, Stream outputStream)
{
    byte[] buffer = new byte[4096];
    int bytesRead;

    while ((bytesRead = inputStream.Read(buffer, 0, buffer.Length)) > 0)
    {
        outputStream.Write(buffer, 0, bytesRead);
    }
}

using System;
using System.IO;

public static void Main()
{
    // 创建两个内存流
    MemoryStream inputStream = new MemoryStream();
    MemoryStream outputStream = new MemoryStream();

    // 向输入流中写入一些数据
    StreamWriter writer = new StreamWriter(inputStream);
    writer.Write("Hello, world!");
    writer.Flush();

    // 将输入流中的数据写入输出流
    CopyStream(inputStream, outputStream);

    // 将输出流中的数据读回到一个字符串
    outputStream.Seek(0, SeekOrigin.Begin);
    StreamReader reader = new StreamReader(outputStream);
    string output = reader.ReadToEnd();

    Console.WriteLine(output);
}