线程间操作无效

Process[] processes=Process.GetProcesses();
        
       private void  theout (object source,System.Timers.ElapsedEventArgs e)
       {
           for (int i = 0; i < processes.GetLength(0); i++)
           {

               listBox1.Items.Clear();
               listBox1.Items.Add(processes[i].ProcessName);

           }

       }

       private void Form1_Load(object sender, EventArgs e)
        {
            System.Timers.Timer t = new System.Timers.Timer(1000);
            t.Elapsed += new System.Timers.ElapsedEventHandler(theout);
            t.AutoReset = true;
            t.Enabled = true;
            
            
               
        }
这个怎么处理啊，最好的处理方式！