winfrom 子窗体调用父窗体中的方法

 public delegate void inis(string str);

  public void inigs(string gs)
        {
            textBox1.Text = gs;
        }

 inis i = new inis(inigs);
            Form5 f5 = new Form5(i);
            f5.Show();

  Form4.inis ii;
        List<string> ls = new List<string>();
        public Form5(Form4.inis ii)
        {
            InitializeComponent();
            this.StartPosition = FormStartPosition.CenterParent;
            this.ii = ii;
        }