Find control in application page?

Question

This line returns null

Button BtnCopy = Page.FindControl("BtnCopy") as Button;

but the control is there in the markup.

<asp:Button ID="BtnCopy" runat="server" 

the entire method is called in the application page load. Its a modal dialog from acustom action

protected void Page_Load(object sender, EventArgs e)
        {
            Logger.LogDebug("CopyRequestToAnotherYear", "Page_Load(object sender, EventArgs e)", "BEGIN");
            string messageSource = Request.Url.ToString();
            string listId = Request.QueryString["ListID"];
            int id = Convert.ToInt32(Request.QueryString["ID"]);
            string state = Request.GetQueryStringValue(SponsoringCommon.Constants.QUERYSTRINGPARAMETER_STATE_NAME);
            string statusMessage = Request.GetQueryStringValue(SponsoringCommon.Constants.QUERYSTRINGPARAMETER_MESSAGE_NAME);
            LoadNextYears(int.Parse(SPContext.Current.Web.Name));
        }


private void LoadNextYears(int currentYear)
    {
        DdlYear.Items.Clear();
        bool yearsExist = false;
        SPSecurity.RunWithElevatedPrivileges(delegate()
        {
            SPWeb currentWeb = SPContext.Current.Web;                    
            using (SPSite site = new SPSite(currentWeb.Url))
            {
                foreach (SPWeb web in site.AllWebs)
                {
                    if (web.WebTemplate == "NLSPONSORINGYEAR" &&  int.Parse(web.Title) > currentYear)
                    {
                        DdlYear.Items.Add(new ListItem(web.Name, web.Name));
                        yearsExist = true;
                    }
                }
            }                
        });

        Button BtnCopy = Page.FindControl("BtnCopy") as Button;
        if (yearsExist)
            BtnCopy.Enabled = true;
        else
            BtnCopy.Enabled = false;
    }




<asp:Content ID="Main" ContentPlaceHolderID="PlaceHolderMain" runat="server">
<table width="100%">
    <tr>
        <td>Year: </td>
        <td><asp:DropDownList ID="DdlYear" runat="server"></asp:DropDownList></td>
    </tr>
    <tr>
        <td colspan="2">
            <asp:Button ID="BtnCopy" runat="server" OnClick="BtnCopy_Click" Text="<%$Resources:SPNLSponsoring, btnCopyToAnotherYear%>"/>
        </td>
    </tr>
</table>
</asp:Content>

Answer 1

Try this -

ContentPlaceHolder content = Page.Master.FindControl("PlaceHolderMain") as ContentPlaceHolder;
Button BtnCopy = content.FindControl("BtnCopy") as Button;

Have not tested the code, but this is the only solution that came into my mind

Answer 2

My question is why you can grab the DropDownList without FindControl, but not the button. They are at the same level and both asp controls.

   `DdlYear.Items.Clear();`

Try using the BtnCopy instance.