Save (Insert) Value (Text) of dynamic TextBox in MasterPage to database in ASP.Net

My Code to be fired During Button 

 protected void Button2_Click(object sender, EventArgs e)
    {

        foreach (Control ctl in Dynamic.Controls)
        {
            if (ctl is TextBox)
            {
                TextBox tb = (TextBox)ctl;
               
                using (SqlConnection con = new SqlConnection(_connStr))
                {
                    using (SqlCommand cmd = new SqlCommand("INSERT INTO DummyEntry(Sanskrit) VALUES(@S)"))
                    {
                        cmd.Connection = con;
                        cmd.Parameters.AddWithValue("@S", tb.Text);
                        con.Open();
                        cmd.ExecuteNonQuery();
                        con.Close();
                    }
                }
            }
        }
}

 PlaceHolder

  <asp:PlaceHolder ID="Dynamic" runat="server">

        </asp:PlaceHolder>

I am not able to find the TextBox inside Placeholder. The Ids are also randomly Generated .I debugged it but the code comes out of foreach loop .