File Stream C#

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
public static class StreamUtil
{
    public static void CopyStream(Stream input, Stream output)
    {
        int bufferSize = 4096;
        byte[] buffer = new byte[bufferSize];
        while (true)
        {
            int read = input.Read(buffer, 0, buffer.Length);
            if (read <= 0)
            {
                return;
            }
            output.Write(buffer, 0, read);
        }
    }
}