C#窗体调用其他窗体textbox值的问题

 #region 变量定义
        Form1 frm = new Form1();
        private void button4_Click(object sender, EventArgs e)
        {
            if (frm.textBox3.Text == "1" )
               {
                  this.Hide();
                  Form2 F2 = new Form2();
                  F2.Show();
                }
            else if (frm.textBox3.Text == "2" )
               {
               this.Hide();
               Form3 F3 = new Form3();
               F3.Show();
                }
        }



    }
}




      #endregion

我在 Form1.Designer.cs中将Textbox3设置为Public

 public System.Windows.Forms.TextBox textBox3;

但是还是无法成功实现，求解答？