BetterCms.Module.Blog.Services.DefaultBlogMLService.TryValidateOldUrl C# (CSharp) Method

        private string TryValidateOldUrl(string url)
        {
            if (string.IsNullOrWhiteSpace(url))
            {
                return null;
            }

            url = urlService.FixUrl(url);
            if (!urlService.ValidateInternalUrl(url))
            {
                var serverPath = httpContextAccessor.MapPublicPath("/").TrimEnd('/');
                if (url.StartsWith(serverPath) && serverPath != url)
                {
                    url = url.Substring(serverPath.Length, url.Length - serverPath.Length);
                    if (!urlService.ValidateInternalUrl(url))
                    {
                        return null;
                    }
                }
                else
                {
                    return null;
                }
            }
            
            return url;
        }