Question

I am using an asp.net formsview in my asp.net page and updatepanel . It has two templates Insertemplate and EditTemplate. Indie both templates there is a dropdownlist with id ddlCountry. I have a dropdownlist with all countries. I am showing states dropdown, if country is US and want to hide the row where states dropdown is shown If country is Non US. I am using following code but it is not working:

protected void ddlCountry_SelectedIndexChanged(object sender, EventArgs e)
    {

        Control c = (Control)sender;
        Control nc = c.NamingContainer;
        if (nc.ID == "fvBillTo" && rblShipSelect.SelectedValue == "billing")
        {
            setShippingAndTaxesDisplay();

            DropDownList ddlCountry = c as DropDownList;
            if (ddlCountry.SelectedItem != null && ddlCountry.SelectedItem.Value == "001")
            {
                HtmlGenericControl trState = nc.FindControl("trState") as HtmlGenericControl;
                trState.Visible = true;
            }
            else
            {
                HtmlGenericControl trState = nc.FindControl("trState") as HtmlGenericControl;
                trState.Visible = false; // code stops here
            }

        }
    }

Answer 1

The code is throwing an exception at that point because it doesn’t have a reference to the table row.

Make sure you have the row referenced as a server side control

<tr id="trState" runat="server"  >

And cast it as a table row instead of a HtmlGenericControl

 System.Web.UI.HtmlControls.HtmlTableRow trState = nc.FindControl("trState") as System.Web.UI.HtmlControls.HtmlTableRow;