在打开的NamedPipeClientStream上重新创建UTF-8 StreamWriter会导致服务器上出现额外的BOM字符

我有一个 NamedPipeServerStream 保持开放 NamedPipeClientStream 保持开放。这个 命名管道服务器流 具有UTF-8 StreamReader 保持开放。这个 NamedPipeClientStream 具有UTF-8 StreamWriter 打开、写入一条消息、关闭然后重新打开以写入另一条消息。两个 StreamReader 以及 StreamWriter 使用打开 leaveOpen 标志设置为true,因此 StreamWriter 无法关闭 NamedPipeClientStream 当它关闭时。到目前为止,一切都很好。

我有一个问题,从第二次 StreamWriter 打开并发送消息时 StreamReader 。我已经设法在一个小的示例程序中重新创建了它。它是在.NET6。这是示例程序的代码:

using System.IO.Pipes;

namespace NamedPipeTest
{
    internal class EncodingTest
    {
        private static NamedPipeServerStream namedPipeServer = new NamedPipeServerStream("mypipe", PipeDirection.InOut, NamedPipeServerStream.MaxAllowedServerInstances, PipeTransmissionMode.Byte, PipeOptions.Asynchronous);
        private static NamedPipeClientStream namedPipeClient = new NamedPipeClientStream(".", "mypipe", PipeDirection.InOut, PipeOptions.Asynchronous);

        static void Main(string[] args)
        {
            Console.WriteLine("Hello! You are the client. Press any key to send a request.");

            Task[] tasks = new Task[]
            {
                Task.Run(() => Server()),
                Task.Run(() => Client())
            };

            Task.WaitAll(tasks);
        }

        static async Task Server()
        {
            if (!namedPipeServer.IsConnected)
            {
                namedPipeServer.WaitForConnection();
            }

            using (var reader = new StreamReader(namedPipeServer, System.Text.Encoding.UTF8, false, 1024, true))
            {
                while (true)
                {
                    string? line = await reader.ReadLineAsync();
                    Console.WriteLine($"Server: Received request: {line}");
                    if (!string.IsNullOrEmpty(line))
                    {
                        var lineBytes = System.Text.Encoding.UTF8.GetBytes(line);
                        var possibleBOMString = System.Text.Encoding.UTF8.GetString(new byte[] { lineBytes[0], lineBytes[1], lineBytes[2] });
                        if (possibleBOMString.Equals("\uFEFF"))
                        {
                            Console.WriteLine("Server: Whoa, what's up with the extra BOM?");
                        }
                    }
                }
            }
        }

        static async Task Client()
        {
            if (!namedPipeClient.IsConnected)
            {
                namedPipeClient.Connect(6000);
            }

            while (true)
            {
                using (var writer = new StreamWriter(namedPipeClient, System.Text.Encoding.UTF8, 1024, true))
                {
                    Console.ReadKey(true);
                    Console.WriteLine("Client: Received key press, sending request.");
                    string? line = "Hello!";
                    await writer.WriteLineAsync(line);
                    await writer.FlushAsync();
                    Console.WriteLine($"Client: Sent request: {line}");
                }
            }
        }
    }
}

该程序的输出为:

Hello! You are the client. Press any key to send a request.
Client: Received key press, sending request.
Server: Received request: Hello!
Client: Sent request: Hello!
Client: Received key press, sending request.
Server: Received request: ?Hello!
Client: Sent request: Hello!
Server: Whoa, what's up with the extra BOM?
Client: Received key press, sending request.
Server: Received request: ?Hello!
Client: Sent request: Hello!
Server: Whoa, what's up with the extra BOM?

这种情况无休止地持续着。因此,该行在发送时不包含额外的BOM,而是在被 StreamReader 。这里发生了什么事?