C# Application ต้องใช้คำสั่งอะไรให้เวลาเราพิพม์ตัวเลขใส่ Texbox แล้วให้แสดงข้อความที่ Label

 private void textBox2_TextChanged(object sender, EventArgs e)
  {

    if (textBox2.Text == "")
            {

            }
            else
            {
                string bb2 = textBox2.Text;
                int all = int.Parse(bb2);
                if (all > 34)
                {
                    label3.Visible = true;
                }
                else
                {
                    label3.Visible = false;

                }
            }    
   }

public static bool CheckKeycode(TextBox targettextbox, char CurrentChar)
        {

            if ((int)CurrentChar >= 45 && (int)CurrentChar <= 57 && (int)CurrentChar != 8 && (int)CurrentChar != 47) 
            {
                return false;   
            }

            if (Convert.ToString (CurrentChar )== "." && targettextbox .Text .IndexOf (".") == -1)
            {
                return false;
            }
            if (CurrentChar == Convert .ToChar (Keys.Back ))
            {
                return false;
            }

            return true;
        }