asp.net多线程编程

我用asp.net web 和window form　都测试过，winform中多了一句System.Windows.Forms.Control.CheckForIllegalCrossThreadCalls = false;线程数目与指定的相同，但是累和结果不对。在asp.net web当中线程数目不与指定数目相同，有时多有时少但都没有达到指定的数目，每次重新计算结果都不一样。

我本人不懂多线程编程的，这些代码是在网上找的
现在问题是：
１、修改代码让其显示结果正确（可以单独做一个循环测试结果是多少，我测试从1累加到1亿是5 000 000 050 000 000）
２、我现在要用多线程批量静态生成，文章数目在3万以上,20万以内，求相关代码，注意效率问题（关于线程编程就可以，分数是另给的100分）

前台代码：

    <div><p>累加开始于：<asp:TextBox ID="txtMinValue" runat="server"></asp:TextBox></p>

        <p>累加结束于：<asp:TextBox ID="txtMaxValue" runat="server"></asp:TextBox></p>

        <p>使用线程数：<asp:TextBox ID="txtThreadNumber" runat="server"></asp:TextBox><asp:Button ID="Button1" runat="server" Text="开始计算" OnClick="Button1_Click" /></p>

        

        <p>累加结果：<asp:TextBox ID="txtOutput" runat="server"></asp:TextBox></p>

        <p>信息：</p>

        <asp:ListBox ID="lstMessage" runat="server" Height="244px" Width="353px"></asp:ListBox>

    </div>

后台代码

    protected void Button1_Click(object sender, EventArgs e)

    {

        txtOutput.Text = "0";

        lstMessage.Items.Clear();

        int threadNumber = Convert.ToInt32(this.txtThreadNumber.Text);

        for (int i = 1; i <= threadNumber; i++)

        {

            try

            {

                Thread thread = new Thread(new ThreadStart(Add));

                thread.Name = i.ToString();

                //thread.Priority = ThreadPriority.Normal;

                thread.Start();

            }

            catch (Exception ex)

            {

                throw new Exception(ex.Message);

            }

            finally

            { 

            

            }

        }

    }

    private void Add()

    {

        DateTime beginTime = DateTime.Now;

        long minValue = long.Parse(txtMinValue.Text);

        long maxValue = long.Parse(txtMaxValue.Text);

        int threadNumber = Convert.ToInt32(txtThreadNumber.Text);

        int thradOrder = Convert.ToInt32(Thread.CurrentThread.Name);

        long step = (maxValue - minValue + 1) / threadNumber;

        long beginValue = minValue + step*(thradOrder-1);

        long result = 0;

        long endValue=beginValue+step;

        for (long i = beginValue; i < endValue; i++)

        {

            result += i;

        }

        lock (this)//线程同步锁

        {

            long sum = long.Parse(txtOutput.Text);

            sum += result;

            txtOutput.Text = sum.ToString();

        }

        DateTime endTime = DateTime.Now;

        TimeSpan timeSpan = endTime - beginTime;

        string message = "线程" + Thread.CurrentThread.Name + ":" + beginValue.ToString() + "到" + endValue.ToString()

            + ",耗时：" + timeSpan.TotalMilliseconds.ToString() + "毫秒";

        this.lstMessage.Items.Add(message);

        Response.Write(message + "<br/>");

        Thread.CurrentThread.Abort();

    }