C#委托：怎么在主窗口调用的线程里写主窗口的控件

C#委托：如何在主窗口调用的线程里写主窗口的控件？
结构简单如下：

C# code

namespace AccessTest{    public  partial class Form1 : Form    {        //public delegate void setCap(string caption);        public Form1()        {            InitializeComponent();        }        private void button1_Click(object sender, EventArgs e)        {            ThreadStart st = new ThreadStart(new DBio().Work);            Thread t = new Thread(st);            t.Start();        }        public void setLog(string cap)        {            this.Text = cap;        }    }    public class DBio    {        public void Work()        {            改写Form1.Text,这里应该这么写呢？        }    }}

C# code

 Form prform;//主窗体 private void FormShow()         {            switch (re_message)            {                ............            }        } MethodInvoker mi = new MethodInvoker(FormShow);                    prform.BeginInvoke(mi);