[Solved] Populate DropDownList based on another not working in ASP.Net

Populating dropdown price and discount by Category dropdown Select is not populating

If i Select dropdown Category to populate price and discount dropdown it is not populating it, the way i did it is, i have a price and discount set page where the admin sets the price and discount, so on the page of sells the sales man will select the dropdown category to populate price and discount from itemprice table, but the populating is not working.

<asp:DropDownList ID="ddlproductcategory" runat="server" OnSelectedIndexChanged="ddlproductcategory_SelectedIndexChanged"
    AutoPostBack="True" AppendDataBoundItems="true" CssClass="form-control pro-edt-select form-control-primary"
    Width="100%">
    <asp:ListItem> --Select Product--</asp:ListItem>
</asp:DropDownList>
<asp:DropDownList ID="ddprice" runat="server" CssClass="btn btn-default dropdown-toggle"
    Width="100%">
    <asp:ListItem> --price load--</asp:ListItem>
</asp:DropDownList>
<asp:DropDownList ID="ddiscount" runat="server" CssClass="btn btn-default dropdown-toggle"
    Width="100%">
    <asp:ListItem> --Discount Load--</asp:ListItem>
</asp:DropDownList>

protected void Page_Load(object sender, EventArgs e)
{
    if (!Page.IsPostBack)
    {
        string conStr = ConfigurationManager.ConnectionStrings["DB"].ConnectionString;
        SqlConnection con = new SqlConnection(conStr);
        DataSet ds = new DataSet();
        try
        {
            con.Open();
            string sql = "SELECT C_ID, Category FROM ItemCategory";
            SqlDataAdapter da = new SqlDataAdapter(sql, con);
            da.Fill(ds);
            ddlproductcategory.DataSource = ds;
            ddlproductcategory.DataTextField = "Category";
            ddlproductcategory.DataValueField = "C_ID";
            ddlproductcategory.DataBind();
        }
        catch (Exception ex)
        {
            Console.WriteLine(ex.Message.ToString());
        }
        finally
        {
            ds.Dispose();
            con.Close();
        }
    }
}

protected void ddlproductcategory_SelectedIndexChanged(object sender, EventArgs e)
{
    SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["DB"].ConnectionString);
    DataSet ds = new DataSet();

    con.Open();
    string sql = "SELECT C_ID, Price FROM Itemprice WHERE C_ID=@C_ID";
    SqlDataAdapter da = new SqlDataAdapter(sql, con);
    da.SelectCommand.Parameters.AddWithValue("@C_ID", ddlproductcategory.SelectedValue);
    da.Fill(ds);
    //
    ddprice.DataSource = ds;
    ddprice.DataTextField = "Price";
    ddprice.DataValueField = "C_ID";
    ddprice.DataBind();
    ///

    SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["DB"].ConnectionString);
    DataSet dss = new DataSet();

    conn.Open();
    string sqll = "SELECT C_ID, Discount FROM Itemprice WHERE C_ID=@C_ID";
    SqlDataAdapter daa = new SqlDataAdapter(sqll, conn);
    daa.SelectCommand.Parameters.AddWithValue("@C_ID", ddlproductcategory.SelectedValue);
    daa.Fill(dss);

    ddiscount.DataSource = dss;
    ddiscount.DataTextField = "Discount";
    ddiscount.DataValueField = "C_ID";
    ddiscount.DataBind();
    dss.Dispose();
    conn.Close();
}