FileStream"无法访问已关闭的文件"

Question

为什么我在使用时收到上述错误消息using (fileStream = new FileStream(path, FileMode.Append, FileAccess.Write))但是当我用它替换它时程序执行得很好fileStream = File.Create(path);？

我想将控制台输出附加到外部文件.这是我的代码:

 //copy console output to file in bin\Debug folder
    class ConsoleCopy : IDisposable
    {
        FileStream fileStream;
        StreamWriter fileWriter;
        TextWriter doubleWriter;
        TextWriter oldOut;
        class DoubleWriter : TextWriter
        {
            TextWriter one;
            TextWriter two;
            public DoubleWriter(TextWriter one, TextWriter two)
            {
                this.one = one;
                this.two = two;
            }
            public override Encoding Encoding
            {
                get { return one.Encoding; }
            }
            //Clears all buffers for the current writer
            public override void Flush()
            {
                one.Flush();

                two.Flush();
            }
            public override void Write(char value)
            {
                **one.Write(value);**//error thrown here
                two.Write(value);
            }
        }
        public ConsoleCopy(string path)
        {
            oldOut = Console.Out;
            try
            {
                **//fileStream = File.Create(path);** //runs alright with this line
                fileWriter = new StreamWriter(fileStream);
                fileWriter.AutoFlush = true;
                doubleWriter = new DoubleWriter(fileWriter, oldOut);
            }
            catch (Exception e)
            {
                Console.WriteLine("Cannot open file for writing");
                Console.WriteLine(e.Message);
                return;
            }
            Console.SetOut(doubleWriter);
        }
        public void Dispose()
        {
            Console.SetOut(oldOut);
            if (fileWriter != null)
            {
                fileWriter.Flush();
                fileWriter.Close();
                fileWriter = null;
            }
            if (fileStream != null)
            {
                fileStream.Close();
                fileStream = null;
            }
        }
    }//end of consoleCopy

我在我的main方法中调用此方法:

 //pass output to ConsoleCopy method for copying to .txt file
        using (var cc = new ConsoleCopy("mylogfile.txt"))
        {
           DateTime theDate = DateTime.UtcNow;

            string custom = theDate.ToString("d");

            Console.WriteLine("User has logged in on " + custom);
        }

更新:

此错误先前显示在one.Write(value).感谢彼得,我设法解决了这个问题.感谢大家的贡献和帮助:)

Answer 1

编辑:如果你在写之前得到它,那是因为我误读了这个问题并将using语句放在ConsoleCopy构造函数中意味着当ConsoleCopy完成创建时,FileStream就会被关闭.当你尝试写它时,因为它已经被关闭了你得到了那个例外.应用相同的解决方案 - 保持FileStream打开并在Dispose()中关闭它,它应该与main方法中的using语句一起使用.

如果我理解正确,你可以处理这个例外,对吗？如果是这样,那是因为正在发生的事情本质上就是你要关闭那个流两次.

using (var cc = new ConsoleCopy("mylogfile.txt"))
{
    // At this time, your filestream is created with the using statement.
    // Writing happens here.
    // Your filestream is closed at the end of the using statement inside of the ConsoleCopy constructor.
} 
// At this point, ConsoleCopy tries to call Dispose(), which flushes and closes everything again. However, this throws an exception because the using statement already closed the FileStream.

如果您的目标是追加到文件的末尾并且Dispose()方法在内部关闭所有内容,那么为什么不直接替换

**//fileStream = File.Create(path);** //runs alright with this line

同

fileStream = File.Open(path, System.IO.FileMode.Append, System.IO.FileAccess.Write);

让你的main中的using语句在内部为你关闭流？