private Control _Control;

        public Form1()
        {
            InitializeComponent();
       }

        private void toolStripTextBox1_KeyUp(object sender, KeyEventArgs e)
        {
            if (e.KeyCode == Keys.Enter)
            {
                if (_Control != null)
                {
                    _Control.Text = toolStripTextBox1.Text;
                }
            }
        }

        private void contextMenuStrip1_Opening(object sender, CancelEventArgs e)
        {
            _Control = contextMenuStrip1.SourceControl;
        }

------解决方案--------------------
楼上的方法很不错  LZ可以多研究 顺便可以了解下他们写出这些代码的思路