Transfer value from usercontrol to form1

//UserControl1
 public partial class UserControl1 : UserControl
    {
        public UserControl1()
        {
            InitializeComponent();
        }
        //Close the UserControl from Form1
        private void label1_Click(object sender, EventArgs e)
        {
            this.Visible = false; 
        }


        public string data = ""; 
        //crystal
        private void button1_Click(object sender, EventArgs e)
        {
            data = "crystal";
            Close();
        }
        //gas
        private void button2_Click(object sender, EventArgs e)
        {
            data = "gas";
            Close();
        }
        //cell
        private void button3_Click(object sender, EventArgs e)
        {
            data = "cell";
            Close();
        }

//--------------------------------------------------------------------------------

//Form1

        private void pictureBox1_Click(object sender, EventArgs e)
        {
            controlClicked = "pictureBox1";
            userControl11.Visible = true;
        }

        
        string mainData = "";
        string controlClicked = "";
        private void userControl11_VisibleChanged(object sender, EventArgs e)
        {
            if (userControl11.Visible == false )
            {
                if (userControl11.data == "crystal")
                {
                    mainData = "crystal";
                    if (controlClicked == "pictureBox1")
                    {
                        pictureBox1.BackgroundImage = Image.FromFile("1.png");
                    }
                }
                if (userControl11.data == "gas")
                {
                    mainData = "gas";
                }
                if (userControl11.data == "cell")
                {
                    mainData = "cell";
                }

                //-------------------------
            }
        }