多线程传递参数之后，如何保证Winform中的控件能够获得

 private void button1_Click(object sender, EventArgs e)
        { 
            FolderBrowserDialog fbd = new FolderBrowserDialog();             if(fbd.ShowDialog(this) == DialogResult.OK)
            {
                DirectoryInfo di = new DirectoryInfo(fbd.SelectedPath); 
                foreach (FileInfo fi in di.GetFiles("*.txt"))
                {
                    ThreadRun run = new ThreadRun(fi.FullName); 
                    Thread t = new Thread(run.ReadFileContent);
                    t.Start(fi.FullName); 
                }
            }
        }
    }     public class ThreadRun 
    {
         StringBuilder sb = new StringBuilder();
         string path;
         public ThreadRun( string path)
         {
             this.path = path;
         }
         public String Path
         {
             get;
             set;
         }         public void  ReadFileContent()
         {
           
             sb.AppendLine(File.ReadAllText(this.path,Encoding.Default)); 
         }
就比如这个例子吧，我通过构造一个类来传递参数的，但是TextBox1如何能够得到sb.ToString()这个的值呢？求指教