<asp:DropDownList ID="cboODMaterial" runat="server" AutoPostBack="true" OnSelectedIndexChanged="btnSelectOD_Click1"
                
                
                style="z-index: 1; left: 168px; top: 18px; position: absolute; width: 143px; height: 22px"
                TabIndex="6">
            </asp:DropDownList>
            <asp:DropDownList ID="cboODStyle" runat="server"
                
                
                style="z-index: 1; left: 409px; top: 17px; position: absolute; width: 248px"
                TabIndex="7" AppendDataBoundItems="True" AutoPostBack="True">
            </asp:DropDownList>

Here is more of the code behind file

 protected void Page_Load(object sender, EventArgs e)
    {
        if (Page.Session["Username"] == null && Page.Session["Username"] == null)
        {
            Response.Redirect("ECPLogin.aspx");
        }

        lblWelcome.Text = "Welcome back " + Session["Username"];
        lblAccountNumber.Text = Session["Username"].ToString();

        if (!IsPostBack)
            LoadLensMaterialList();
    
    if(!IsPostBack)
       btnSelectOD_Click1(null, null);
           
     }

    private void LoadLensMaterialList()
    {
        SqlConnection conn;
        SqlCommand comm;
        SqlDataReader reader;

        //  Read the connection string from Web.Config

        string connectionString =
         ConfigurationManager.ConnectionStrings["ValueVision"].ConnectionString;


        // Initialize Connection
        conn = new SqlConnection(connectionString);

        comm = new SqlCommand("SELECT LensID, Material FROM ECPLenses", conn);

        //  Error handling for database code
        try
        {
            //Open the connection
            conn.Open();

            reader = comm.ExecuteReader();
            cboODMaterial.DataSource = reader;
            cboODMaterial.DataValueField = "LensID";
            cboODMaterial.DataTextField = "Material";
            cboODMaterial.DataBind();

            //Close the reader
            reader.Close();
        }
        catch
        {
            lblError.Text = "* An error occurred retrieving a list of Available Lenses..";
        }
        finally
        {
            //Close the connection
            conn.Close();
        }
    }
    protected void btnSelectOD_Click1(object sender, EventArgs e)
    {
        {
            // Response.Write("Filling");

            SqlConnection conn;
            SqlCommand comm;
            SqlDataReader reader;

            //  Read the connection string from Web.Config

            string connectionString =
             ConfigurationManager.ConnectionStrings["ValueVision"].ConnectionString;


            // Initialize Connection
            conn = new SqlConnection(connectionString);

            comm = new SqlCommand("SELECT ECPLensType1.*, ECPLenses.Material FROM ECPLenses INNER JOIN ECPLensType1 ON ECPLensType1.LensID = ECPLenses.LensID WHERE ECPLensType1.LensID=" + cboODMaterial.SelectedItem.Value, conn);


            //  Error handling for database code
            try
            {
                //Open the connection
                conn.Open();

                reader = comm.ExecuteReader();
                cboODStyle.DataSource = reader;
                cboODStyle.DataValueField = "LensID";
                cboODStyle.DataTextField = "Description";
                cboODStyle.DataBind();

                //Close the reader
                reader.Close();
            }
            catch
            {
                lblError.Text = "* An error occurred retrieving a list of Available Lenses..";
            }
            finally
            {
                //Close the connection
                conn.Close();
            }
        }

    }
    
    protected void btnSubmit_Click(object sender, EventArgs e)
    {
       
        SqlConnection conn;
        SqlCommand comm;
        string connectionString = ConfigurationManager.ConnectionStrings["ValueVision"].ConnectionString;

        conn = new SqlConnection(connectionString);
        comm = new SqlCommand(
            "INSERT INTO OrdersDB (AccountNumber, Username, Lastname, Firstname, JobType, OrderType, ODMaterial, ODStyle, " +

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