线程间操作无效

//建立个委托
        private delegate void ShowDelegate(string strshow);

        public void Show(string strshow)

        {

            if (this.txtreceive.InvokeRequired)

            {

             //   this.txtreceive.BeginInvoke(new ShowDelegate(Show), strshow);//这个也可以

                this.txtreceive.Invoke(new ShowDelegate(Show), strshow);

            }

            else

            {

                    this.txtreceive.Text += strshow;

            }

        }