如何在c#中从webbrowser中获取html value属性的值？

using System;
using System.Windows.Forms;

namespace WebBrowserExample
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            webBrowser1.DocumentCompleted += WebBrowser1_DocumentCompleted;
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            webBrowser1.Navigate("https://example.com"); // 替换为你要加载的网页地址
        }

        private void WebBrowser1_DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e)
        {
            HtmlElement element = webBrowser1.Document.GetElementById("elementId"); // 替换为你要获取value属性的元素的id
            if (element != null)
            {
                string value = element.GetAttribute("value");
                MessageBox.Show("Value属性值为：" + value);
            }
        }
    }
}