一个简单的 委托

        public delegate void InvokeDelegate(string x);

        public void OnFaxSended(string fax)
        {
            //txtFax.Text += fax;
            //txtFax.Text += System.Environment.NewLine;
            txtFax.BeginInvoke(new InvokeDelegate(InvokeMethod),fax);
        }

        public void InvokeMethod(string x)
        {
            txtFax.Text += x;
            txtFax.Text += System.Environment.NewLine;
        }