Admin.Posts.AddEntry.BtnCategoryClick C# (CSharp) Method

        private void BtnCategoryClick(object sender, EventArgs e)
        {
            if (!Page.IsValid)
            {
                return;
            }

            var cat = new Category(txtCategory.Text, string.Empty);
            cat.Save();
            var item = new ListItem(Server.HtmlEncode(txtCategory.Text), cat.Id.ToString())
                {
                    Selected = true
                };
            string catHtml = string.Format("<input type=\"checkbox\" id=\"{0}\">", cat.Id);
            catHtml += string.Format("<label>{0}</label><br/>", Server.HtmlEncode(cat.Title));
            cblCategories.InnerHtml += catHtml;

            string postId = Request.QueryString["id"];
            Post post = null;

            // Security Rights validation

            if (postId == null)
            {
                Security.DemandUserHasRight(Rights.CreateNewPosts, true);
                post = new Post();
            }
            else
            {
                post = Post.GetPost(new Guid(postId));

                if (post.CurrentUserOwns)
                {
                    Security.DemandUserHasRight(Rights.EditOwnPosts, true);
                }
                else
                {
                    Security.DemandUserHasRight(Rights.EditOtherUsersPosts, true);
                }
            }
        }