要在.NET Framework 4.8中使用C#实现离线实时语音识别，可以使用开源库Vosk（支持离线ASR）配合音频处理库NAudio。

步骤 1：安装依赖库
1.1.
安装NuGet包：
- Install-Package NAudio（处理音频输入）
- Install-Package Vosk（离线语音识别引擎）
2.2.
下载语音模型：
- 前往 Vosk Models 下载适合的模型（如小型英文模型 vosk-model-small-en-us-0.15）。
- 解压模型到项目目录（如 Models/vosk-model-small-en-us-0.15）。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using NAudio.Wave;
using Vosk;
using System.Windows.Forms;
namespace 语音识别
{
public class RealTimeSpeechRecognizer
{
    private readonly VoskRecognizer _recognizer;
    private readonly WaveInEvent _waveIn;
    private readonly RichTextBox _rtb;

    public RealTimeSpeechRecognizer(string modelPath, RichTextBox rtb)
    {
        _rtb = rtb;

        // 初始化Vosk
        Model model = new Model(modelPath);
        _recognizer = new VoskRecognizer(model, 16000.0f);
        _recognizer.SetWords(true);

        // 初始化音频输入
        _waveIn = new WaveInEvent
        {
            WaveFormat = new WaveFormat(16000, 16, 1),
            DeviceNumber = 0
        };
        _waveIn.DataAvailable += OnAudioDataAvailable;
    }

    public void StartListening() => _waveIn.StartRecording();
    public void StopListening() => _waveIn.StopRecording();

    

    // 解析JSON结果（兼容部分结果）
    private string ParseJsonResult(string json, bool isPartial = false)
    {
        dynamic obj = Newtonsoft.Json.JsonConvert.DeserializeObject(json);
        return isPartial ? obj.partial : obj.text;
    }

    // 线程安全更新RichTextBox
    private void ShowText(string text)
    {
        if (_rtb.InvokeRequired)
        {
            _rtb.BeginInvoke(new Action<string>(ShowText), text);
        }
        else
        {
            _rtb.AppendText(text);
            _rtb.ScrollToCaret();
        }
    }

    // 其他字段和构造函数保持不变...
    private string _lastPartialText = string.Empty;

    

    private void OnAudioDataAvailable(object sender, WaveInEventArgs e)
    {
        if (_recognizer.AcceptWaveform(e.Buffer, e.BytesRecorded))
        {
            string result = ParseJsonResult(_recognizer.Result());
            ClearLastPartial(); // 清理临时部分
            AppendFinalText(result);
        }
        else
        {
            string partial = ParseJsonResult(_recognizer.PartialResult(), isPartial: true);
            UpdatePartialText(partial);
        }
    }

    private void UpdatePartialText(string newPartial)
    {
        if (newPartial == _lastPartialText) return;

        // 在主线程更新UI
        _rtb.BeginInvoke(new Action(() =>
        {
            int selectionStart = _rtb.TextLength - _lastPartialText.Length;

            // 删除旧临时内容
            if (selectionStart >= 0 && _lastPartialText.Length > 0)
            {
                _rtb.Select(selectionStart, _lastPartialText.Length);
                _rtb.SelectedText = "";
            }

            // 追加新内容
            _rtb.AppendText(newPartial);
            _rtb.ScrollToCaret();

            // 更新临时记录
            _lastPartialText = newPartial;
        }));
    }

    private void AppendFinalText(string text)
    {
        _rtb.BeginInvoke(new Action(() =>
        {
            _rtb.AppendText(text + "\n");
            _lastPartialText = string.Empty; // 重置临时部分
        }));
    }

    private void ClearLastPartial()
    {
        if (string.IsNullOrEmpty(_lastPartialText)) return;

        _rtb.BeginInvoke(new Action(() =>
        {
            int start = _rtb.TextLength - _lastPartialText.Length;
            if (start >= 0)
            {
                _rtb.Select(start, _lastPartialText.Length);
                _rtb.SelectedText = "";
            }
        }));
    }
}

}

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
namespace 语音识别
{
public partial class Form1 : Form
{
private RealTimeSpeechRecognizer _recognizer;
public Form1()
{
InitializeComponent();
btnStop.Enabled = false;
}
    private void button1_Click(object sender, EventArgs e)
    {
        _recognizer.StopListening();
        btnStart.Enabled = true;
        btnStop.Enabled = false;
    }
    

    private void btnStart_Click(object sender, EventArgs e)
    {
        string modelPath = @"E:\Models\vosk-model-small-cn-0.22"; // 中文模型路径
        _recognizer = new RealTimeSpeechRecognizer(modelPath, richTextBox1);

        btnStart.Enabled = false;
        btnStop.Enabled = true;
        _recognizer.StartListening();
    }
}

}