การfindControl ใน even Load เพื่อหาddlที่อยู่ในgridview

protected void Page_Load(object sender, EventArgs e)
    {
        DropDownList ddlFac = (DropDownList)gvEdit.Rows[0].Cells[7].FindControl("ddlFac");
        HiddenField hdFacID = (HiddenField)gvEdit.Rows[0].Cells[8].FindControl("hdFacID");
        if (ddlFac.SelectedValue != null) // error=>Object reference not set to an instance of an object.
        {
            hdFacID.Value = ddlFac.SelectedValue;

        }
        else { hdFacID.Value = "1"; }
       
    }