输出流写入的内容多于读取的内容-C#

Question

我有一个脑死亡的时刻，茫然地盯着这小段代码看了10分钟。。。有人能告诉我为什么输出文件（test2.txt）比它正在读取的文件（test.txt）包含更多的文本吗？？

这是代码：

FileStream inputStream = new FileStream(@"C:Temptest.txt", FileMode.Open);
FileStream outputStream = new FileStream(@"C:Temptest2.txt", FileMode.OpenOrCreate);
byte[] buffer = new byte[1024];
Console.WriteLine(new FileInfo(@"C:Temptest.txt").Length + "n");
while (inputStream.Read(buffer, 0, buffer.Length) > 0)
{
      Console.WriteLine("bufferlength " + buffer.Where(x => x != 0).ToArray().Length);
      Console.WriteLine(new FileInfo(@"C:Temptest2.txt").Length);
      outputStream.Write(buffer, 0, buffer.Length);
      outputStream.Flush();
      Console.ReadKey();
}
Console.WriteLine("n" + inputStream.Length);
Console.WriteLine(outputStream.Length);
Console.Read();

谢谢各位

Answer 1

这是因为您创建了一个大小为1024的字节数组。因此，即使inputStream长度小于1024，它仍然会向文件写入1024字节。

您应该使用inputStream大小对其进行初始化，以便只有有限的字节写入您的文件：

byte[] buffer = new byte[inputStream.Length];

更新

Silvermind在评论中指出对，让缓冲区数组大小为1024。相反，use byte size returned by Read方法写入文件，以便只有读取的字节才能写入文件：

int bytesRead;
while ((bytesRead = inputStream.Read(buffer, 0, buffer.Length)) > 0)
{
    Console.WriteLine("bufferlength " + buffer.Where(x => x != 0)
                                                  .ToArray().Length);
    Console.WriteLine(new FileInfo(@"D:Temptest2.txt").Length);
    outputStream.Write(buffer, 0, bytesRead); <- HERE
    outputStream.Flush();
}

---

顺便说一句，使用后应该使用dispose FileStream's，以避免任何内存泄漏。您可以使用wrap them in using block，它会在使用后自动为您处理。

using (FileStream inputStream = new FileStream(@"C:Temptest.txt",
                                                 FileMode.Open))
{
    using (FileStream outputStream = new FileStream(@"C:Temptest2.txt",
                                                      FileMode.OpenOrCreate))
    {
        byte[] buffer = new byte[inputStream.Length];
        Console.WriteLine(new FileInfo(@"C:Temptest.txt").Length + "n");
        int bytesRead;
        while ((bytesRead = inputStream.Read(buffer, 0, buffer.Length)) > 0)
        {
            Console.WriteLine("bufferlength " + buffer.Where(x => x != 0)
                                                  .ToArray().Length);
            Console.WriteLine(new FileInfo(@"D:Temptest2.txt").Length);
            outputStream.Write(buffer, 0, bytesRead); <- HERE
            outputStream.Flush();
         }
        Console.WriteLine("n" + inputStream.Length);
        Console.WriteLine(outputStream.Length);
    }
}