Fixing blog permalinks in front matter

Program.cs

using System;
using System.IO;
using System.Linq;
using System.Threading.Tasks;
using Markdig;
using Markdig.Extensions.Yaml;
using Markdig.Syntax;
using YamlDotNet.Serialization;

namespace blogFix
{
    /// <summary>
    /// Most code from https://khalidabuhakmeh.com/parse-markdown-front-matter-with-csharp
    /// </summary>
    internal class Program
    {
        private static readonly MarkdownPipeline Pipeline
            = new MarkdownPipelineBuilder()
                // YAML Front Matter extension registered
                .UseYamlFrontMatter()
                .Build();

        private static async Task Main(string[] args)
        {
            Console.WriteLine("Fixing blog!");

            var directory = Directory
                .GetFiles(@"C:\Users\laure\projects\blog\source\_posts");

            var fileContent = directory.Select(f => new {file = f, fileContent = File.ReadAllText(f)});
            
            var posts = fileContent
                .Select(md => new {file = md.file, fileContent = md.fileContent, fileFrontMatter = md.fileContent.GetFrontMatter<BlogFrontMatter>()})
                .ToList();

            foreach (var post in posts.OrderBy(p => p.fileFrontMatter.Date))
            {
                Console.WriteLine($"/{post.fileFrontMatter.Date.Year}/{post.fileFrontMatter.Date.Month:00}/{post.fileFrontMatter.Date.Day:00}/{post.fileFrontMatter.Permalink}/");

                await ReplacePermalink(post.file, post.fileFrontMatter);
            }
        }

        private static async Task ReplacePermalink(string file, BlogFrontMatter fileFrontMatter)
        {
            var allLines = await File.ReadAllLinesAsync(file);

            var lines = allLines.ToList();

            for (var index = 0; index < allLines.ToList().Count; index++)
            {

                if (lines[index].StartsWith("permalink"))
                {
                    lines[index] = "permalink: " +
                           $"/{fileFrontMatter.Date.Year}/{fileFrontMatter.Date.Month:00}/{fileFrontMatter.Date.Day:00}/{fileFrontMatter.Permalink}/";
                }
            }
            
            await File.WriteAllLinesAsync(file, lines);
        }
    }

    public class BlogFrontMatter
    {
        // [YamlMember(Alias = "tags")]
        // public string Tags { get; set; }

        [YamlMember(Alias = "title")] public string Title { get; set; }

        [YamlMember(Alias = "permalink")] public string Permalink { get; set; }

        [YamlMember(Alias = "date")] public DateTime Date { get; set; }

        [YamlMember(Alias = "image")] public string Image { get; set; }

        [YamlMember(Alias = "image_credit_name")]
        public string ImageCreditName { get; set; }

        [YamlMember(Alias = "image_credit_url")]
        public string ImageCreditUrl { get; set; }

        [YamlMember(Alias = "image_alt")] public string ImageAlt { get; set; }

        [YamlMember(Alias = "redirect_from")] public string[] RedirectFrom { get; set; }

        // [YamlIgnore]
        // public IList<string> GetTags => Tags?
        //     .Split(",", StringSplitOptions.RemoveEmptyEntries)
        //     .Select(x => x.Trim())
        //     .ToArray();
    }

    public static class MarkdownExtensions
    {
        private static readonly Deserializer YamlDeserializer =
            new DeserializerBuilder()
                .IgnoreUnmatchedProperties()
                .Build();

        private static readonly MarkdownPipeline Pipeline
            = new MarkdownPipelineBuilder()
                .UseYamlFrontMatter()
                .Build();

        public static T GetFrontMatter<T>(this string markdown)
        {
            var document = Markdown.Parse(markdown, Pipeline);
            var block = document
                .Descendants<YamlFrontMatterBlock>()
                .FirstOrDefault();

            if (block == null)
                return default;

            var yaml =
                block
                    // this is not a mistake
                    // we have to call .Lines 2x
                    .Lines // StringLineGroup[]
                    .Lines // StringLine[]
                    .OrderByDescending(x => x.Line)
                    .Select(x => $"{x}\n")
                    .ToList()
                    .Select(x => x.Replace("---", string.Empty))
                    .Where(x => !string.IsNullOrWhiteSpace(x))
                    .Aggregate((s, agg) => agg + s);

            return YamlDeserializer.Deserialize<T>(yaml);
        }
    }
}