C# qq空间登录用的webbrowser 报错
调试的时候地址：http://user.qzone.qq.com/号码，试了好多次，偶尔能登陆成功，不成功的时候报错：未将对象引用设置到对象的实例，位置在代码那里注释出了，有时候也报错：“0”的值对于“index”无效 index”应介于 0 和 -1 之间，也是那个位置，我自己觉得可能是文档没完全加载或者线程问题，C#不熟，大家帮忙是什么原因或者怎么调整，代码也不多，谢谢大家

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

namespace ReadCSV
{
    public partial class Form1 : Form
    {

        Thread loginThread1 = null;
        Thread loginThread2 = null;
        Mutex mutex = null;
        public delegate void webBrowserDocReq();
        private webBrowserDocReq wbdr;

        public Form1()
        {
            InitializeComponent();
            this.wbdr = new webBrowserDocReq(loginMethod);
        }     

        private void buttonLogin_Click(object sender, EventArgs e)
        {
            loginThread1 = new Thread(btnNavi);
            loginThread2 = new Thread(btnLogin);
            mutex = new Mutex();
            loginThread1.Start();
            loginThread2.Start();
        }
        private void btnNavi() 
        {
            lock (this)
            {
                mutex.WaitOne();
                webBrowser1.Navigate(new Uri(textUrl.Text.ToString()));
                Thread.Sleep(2000);
                mutex.ReleaseMutex();
            }
        }
        private void btnLogin()
        {

            lock (this)
            {
                mutex.WaitOne();
                webBrowser1.Invoke(this.wbdr);//总是在这报错                
                Thread.Sleep(1500);
                mutex.ReleaseMutex();
            }
        }
        private void loginMethod()
        {
            HtmlDocument doc = webBrowser1.Document.Window.Frames[0].Document;
            doc.GetElementById("u").InnerText = textName.Text;
            doc.GetElementById("p").InnerText = textPwd.Text;
            doc.GetElementById("login_button").InvokeMember("click");

        }

        private void textUrl_TextChanged(object sender, EventArgs e)
        {
         
        }

 
        private void webBrowser1_DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e)
        {

        }

        private void Form1_Load(object sender, EventArgs e)
        { 
 

        }

        private void label2_Click(object sender, EventArgs e)
        {

        }

        private void label3_Click(object sender, EventArgs e)
        {

        }

        private void label1_Click(object sender, EventArgs e)
        {

        }

        private void textName_TextChanged_1(object sender, EventArgs e)
        {

        }

        private void textPwd_TextChanged_1(object sender, EventArgs e)
        {

        }

        private void webBrowser1_DocumentCompleted_1(object sender, WebBrowserDocumentCompletedEventArgs e)
        {

        }
    }
}

[解决办法]
晕，我觉得简单问题被楼主搞得复杂化了，楼主应该只是要实现打开网页，打开之后往页面上的输入框输入东西，然后点击登录吧。
这又是线程，又是互斥对象的，完全没必要啊
webbrowser导航到页面之后，从DocumentCompleted事件里面判断页面是否打开完成，打开完成，直接调用你loginMethod方法就可以了啊
[解决办法]
应该是文档没加载完就赋值找不到对象?

没测试过 不过你可以看看那个DocumentCompleted在赋值 应该不错