https://ask.csdn.net/questions/749719 采纳后帮你写一个。

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Diagnostics;
using System.Threading;
using SHDocVw;

namespace Q749719
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        SHDocVw.InternetExplorer ie;

        private void button1_Click(object sender, EventArgs e)
        {
            ie = new SHDocVw.InternetExplorer();
            ie.DocumentComplete += new SHDocVw.DWebBrowserEvents2_DocumentCompleteEventHandler(ie_DocumentComplete);
            complete = false;
            ie.Navigate("http://www.baidu.com");
            ie.Visible = true;
            while (!complete)
            {
                Application.DoEvents();
                Thread.Sleep(1000);
            }            
        }

        bool complete = false;

        private void button2_Click(object sender, EventArgs e)
        {
            var doc = ie.Document;
            doc.getElementById("kw").innerText = textBox1.Text;
        }

        void ie_DocumentComplete(object pDisp, ref object URL)
        {
            complete = true;
        }

        private void button3_Click(object sender, EventArgs e)
        {
            var doc = ie.Document;
            doc.getElementById("su").click();
        }
    }
}