Use nullable

DiscordChatExporter.Cli/Commands/ExportCommandBase.cs

@@ -7,7 +7,6 @@ using CliFx.Utilities;
 using DiscordChatExporter.Core.Models;
 using DiscordChatExporter.Core.Services;
 using DiscordChatExporter.Core.Services.Helpers;
-using Tyrrrz.Extensions;
 
 namespace DiscordChatExporter.Cli.Commands
 {
@@ -22,7 +21,7 @@ namespace DiscordChatExporter.Cli.Commands
         public ExportFormat ExportFormat { get; set; } = ExportFormat.HtmlDark;
 
         [CommandOption("output", 'o', Description = "Output file or directory path.")]
-        public string OutputPath { get; set; }
+        public string? OutputPath { get; set; }
 
         [CommandOption("after",Description = "Limit to messages sent after this date.")]
         public DateTimeOffset? After { get; set; }
@@ -34,7 +33,7 @@ namespace DiscordChatExporter.Cli.Commands
         public int? PartitionLimit { get; set; }
 
         [CommandOption("dateformat", Description = "Date format used in output.")]
-        public string DateFormat { get; set; }
+        public string? DateFormat { get; set; }
 
         protected ExportCommandBase(SettingsService settingsService, DataService dataService, ExportService exportService)
             : base(dataService)
@@ -46,8 +45,8 @@ namespace DiscordChatExporter.Cli.Commands
         protected async Task ExportChannelAsync(IConsole console, Channel channel)
         {
             // Configure settings
-            if (!DateFormat.IsNullOrWhiteSpace())
+            if (!string.IsNullOrWhiteSpace(DateFormat))
-                SettingsService.DateFormat = DateFormat;
+                SettingsService.DateFormat = DateFormat!;
 
             console.Output.Write($"Exporting channel [{channel.Name}]... ");
             var progress = console.CreateProgressTicker();
@@ -57,7 +56,7 @@ namespace DiscordChatExporter.Cli.Commands
 
             // Generate file path if not set or is a directory
             var filePath = OutputPath;
-            if (filePath.IsNullOrWhiteSpace() || ExportHelper.IsDirectoryPath(filePath))
+            if (string.IsNullOrWhiteSpace(filePath) || ExportHelper.IsDirectoryPath(filePath))
             {
                 // Generate default file name
                 var fileName = ExportHelper.GetDefaultExportFileName(ExportFormat, chatLog.Guild,

DiscordChatExporter.Cli/DiscordChatExporter.Cli.csproj

@@ -6,13 +6,14 @@
     <Version>2.15</Version>
     <Company>Tyrrrz</Company>
     <Copyright>Copyright (c) Alexey Golub</Copyright>
+    <Nullable>enable</Nullable>
     <ApplicationIcon>..\favicon.ico</ApplicationIcon>
   </PropertyGroup>
 
   <ItemGroup>
     <PackageReference Include="CliFx" Version="0.0.7" />
     <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="3.0.0" />
-    <PackageReference Include="Tyrrrz.Extensions" Version="1.6.3" />
+    <PackageReference Include="Tyrrrz.Extensions" Version="1.6.5" />
   </ItemGroup>
 
   <ItemGroup>

DiscordChatExporter.Core.Markdown/DiscordChatExporter.Core.Markdown.csproj

@@ -2,10 +2,11 @@
 
   <PropertyGroup>
     <TargetFramework>netcoreapp3.0</TargetFramework>
+    <Nullable>enable</Nullable>
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Tyrrrz.Extensions" Version="1.6.3" />
+    <PackageReference Include="Tyrrrz.Extensions" Version="1.6.5" />
   </ItemGroup>
 
 </Project>

DiscordChatExporter.Core.Markdown/Internal/AggregateMatcher.cs

@@ -16,9 +16,9 @@ namespace DiscordChatExporter.Core.Markdown.Internal
         {
         }
 
-        public ParsedMatch<T> Match(StringPart stringPart)
+        public ParsedMatch<T>? Match(StringPart stringPart)
         {
-            ParsedMatch<T> earliestMatch = null;
+            ParsedMatch<T>? earliestMatch = null;
 
             // Try to match the input with each matcher and get the match with the lowest start index
             foreach (var matcher in _matchers)

DiscordChatExporter.Core.Markdown/Internal/IMatcher.cs

@@ -2,6 +2,6 @@
 {
     internal interface IMatcher<T>
     {
-        ParsedMatch<T> Match(StringPart stringPart);
+        ParsedMatch<T>? Match(StringPart stringPart);
     }
 }

DiscordChatExporter.Core.Markdown/Internal/RegexMatcher.cs

@@ -1,8 +1,4 @@
 using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Linq.Expressions;
-using System.Reflection;
 using System.Text.RegularExpressions;
 
 namespace DiscordChatExporter.Core.Markdown.Internal
@@ -23,7 +19,7 @@ namespace DiscordChatExporter.Core.Markdown.Internal
         {
         }
 
-        public ParsedMatch<T> Match(StringPart stringPart)
+        public ParsedMatch<T>? Match(StringPart stringPart)
         {
             var match = _regex.Match(stringPart.Target, stringPart.StartIndex, stringPart.Length);
             if (!match.Success)

DiscordChatExporter.Core.Markdown/Internal/StringMatcher.cs

@@ -20,7 +20,7 @@ namespace DiscordChatExporter.Core.Markdown.Internal
         {
         }
 
-        public ParsedMatch<T> Match(StringPart stringPart)
+        public ParsedMatch<T>? Match(StringPart stringPart)
         {
             var index = stringPart.Target.IndexOf(_needle, stringPart.StartIndex, stringPart.Length, _comparison);
 

DiscordChatExporter.Core.Markdown/MarkdownParser.cs

@@ -3,7 +3,6 @@ using System.Linq;
 using System.Text.RegularExpressions;
 using DiscordChatExporter.Core.Markdown.Internal;
 using DiscordChatExporter.Core.Markdown.Nodes;
-using Tyrrrz.Extensions;
 
 namespace DiscordChatExporter.Core.Markdown
 {
@@ -125,7 +124,7 @@ namespace DiscordChatExporter.Core.Markdown
         // Capture <:lul:123456> or <a:lul:123456>
         private static readonly IMatcher<Node> CustomEmojiNodeMatcher = new RegexMatcher<Node>(
             new Regex("<(a)?:(.+?):(\\d+?)>", DefaultRegexOptions),
-            m => new EmojiNode(m.Groups[3].Value, m.Groups[2].Value, !m.Groups[1].Value.IsNullOrWhiteSpace()));
+            m => new EmojiNode(m.Groups[3].Value, m.Groups[2].Value, !string.IsNullOrWhiteSpace(m.Groups[1].Value)));
 
         /* Links */
 

DiscordChatExporter.Core.Markdown/Nodes/EmojiNode.cs

@@ -1,18 +1,16 @@
-using Tyrrrz.Extensions;
+namespace DiscordChatExporter.Core.Markdown.Nodes
-
-namespace DiscordChatExporter.Core.Markdown.Nodes
 {
     public class EmojiNode : Node
     {
-        public string Id { get; }
+        public string? Id { get; }
 
         public string Name { get; }
 
         public bool IsAnimated { get; }
 
-        public bool IsCustomEmoji => !Id.IsNullOrWhiteSpace();
+        public bool IsCustomEmoji => !string.IsNullOrWhiteSpace(Id);
 
-        public EmojiNode(string id, string name, bool isAnimated)
+        public EmojiNode(string? id, string name, bool isAnimated)
         {
             Id = id;
             Name = name;

DiscordChatExporter.Core.Models/Channel.cs

@@ -6,17 +6,17 @@
     {
         public string Id { get; }
 
-        public string ParentId { get; }
+        public string? ParentId { get; }
 
-        public string GuildId { get; }
+        public string? GuildId { get; }
 
         public string Name { get; }
 
-        public string Topic { get; }
+        public string? Topic { get; }
 
         public ChannelType Type { get; }
 
-        public Channel(string id, string parentId, string guildId, string name, string topic, ChannelType type)
+        public Channel(string id, string? parentId, string? guildId, string name, string? topic, ChannelType type)
         {
             Id = id;
             ParentId = parentId;

DiscordChatExporter.Core.Models/DiscordChatExporter.Core.Models.csproj

@@ -2,10 +2,11 @@
 
   <PropertyGroup>
     <TargetFramework>netcoreapp3.0</TargetFramework>
+    <Nullable>enable</Nullable>
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Tyrrrz.Extensions" Version="1.6.3" />
+    <PackageReference Include="Tyrrrz.Extensions" Version="1.6.5" />
   </ItemGroup>
 
 </Project>

DiscordChatExporter.Core.Models/Embed.cs

@@ -8,28 +8,29 @@ namespace DiscordChatExporter.Core.Models
 
     public class Embed
     {
-        public string Title { get; }
+        public string? Title { get; }
 
-        public string Url { get; }
+        public string? Url { get; }
 
         public DateTimeOffset? Timestamp { get; }
 
+        // TODO: this should be nullable and default color should be set in CSS
         public Color Color { get; }
 
-        public EmbedAuthor Author { get; }
+        public EmbedAuthor? Author { get; }
 
-        public string Description { get; }
+        public string? Description { get; }
 
         public IReadOnlyList<EmbedField> Fields { get; }
 
-        public EmbedImage Thumbnail { get; }
+        public EmbedImage? Thumbnail { get; }
 
-        public EmbedImage Image { get; }
+        public EmbedImage? Image { get; }
 
-        public EmbedFooter Footer { get; }
+        public EmbedFooter? Footer { get; }
 
-        public Embed(string title, string url, DateTimeOffset? timestamp, Color color, EmbedAuthor author, string description,
+        public Embed(string? title, string? url, DateTimeOffset? timestamp, Color color, EmbedAuthor? author, string? description,
-            IReadOnlyList<EmbedField> fields, EmbedImage thumbnail, EmbedImage image, EmbedFooter footer)
+            IReadOnlyList<EmbedField> fields, EmbedImage? thumbnail, EmbedImage? image, EmbedFooter? footer)
         {
             Title = title;
             Url = url;
@@ -43,6 +44,6 @@ namespace DiscordChatExporter.Core.Models
             Footer = footer;
         }
 
-        public override string ToString() => Title;
+        public override string ToString() => Title ?? "<untitled embed>";
     }
 }

DiscordChatExporter.Core.Models/EmbedAuthor.cs

@@ -4,19 +4,19 @@ namespace DiscordChatExporter.Core.Models
 
     public class EmbedAuthor
     {
-        public string Name { get; }
+        public string? Name { get; }
 
-        public string Url { get; }
+        public string? Url { get; }
 
-        public string IconUrl { get; }
+        public string? IconUrl { get; }
 
-        public EmbedAuthor(string name, string url, string iconUrl)
+        public EmbedAuthor(string? name, string? url, string? iconUrl)
         {
             Name = name;
             Url = url;
             IconUrl = iconUrl;
         }
 
-        public override string ToString() => Name;
+        public override string ToString() => Name ?? "<unnamed author>";
     }
 }

DiscordChatExporter.Core.Models/EmbedFooter.cs

@@ -6,9 +6,9 @@ namespace DiscordChatExporter.Core.Models
     {
         public string Text { get; }
 
-        public string IconUrl { get; }
+        public string? IconUrl { get; }
 
-        public EmbedFooter(string text, string iconUrl)
+        public EmbedFooter(string text, string? iconUrl)
         {
             Text = text;
             IconUrl = iconUrl;

DiscordChatExporter.Core.Models/EmbedImage.cs

@@ -4,13 +4,13 @@ namespace DiscordChatExporter.Core.Models
 
     public class EmbedImage
     {
-        public string Url { get; }
+        public string? Url { get; }
 
         public int? Width { get; }
 
         public int? Height { get; }
 
-        public EmbedImage(string url, int? width, int? height)
+        public EmbedImage(string? url, int? width, int? height)
         {
             Url = url;
             Height = height;

DiscordChatExporter.Core.Models/Emoji.cs

@@ -8,7 +8,7 @@ namespace DiscordChatExporter.Core.Models
 
     public partial class Emoji
     {
-        public string Id { get; }
+        public string? Id { get; }
 
         public string Name { get; }
 
@@ -16,7 +16,7 @@ namespace DiscordChatExporter.Core.Models
 
         public string ImageUrl { get; }
 
-        public Emoji(string id, string name, bool isAnimated)
+        public Emoji(string? id, string name, bool isAnimated)
         {
             Id = id;
             Name = name;
@@ -37,10 +37,10 @@ namespace DiscordChatExporter.Core.Models
         private static string GetTwemojiName(string emoji) =>
             GetCodePoints(emoji).Select(i => i.ToString("x")).JoinToString("-");
 
-        public static string GetImageUrl(string id, string name, bool isAnimated)
+        public static string GetImageUrl(string? id, string name, bool isAnimated)
         {
             // Custom emoji
-            if (!id.IsNullOrWhiteSpace())
+            if (!string.IsNullOrWhiteSpace(id))
             {
                 // Animated
                 if (isAnimated)

DiscordChatExporter.Core.Models/Guild.cs

@@ -1,8 +1,6 @@
-using Tyrrrz.Extensions;
+namespace DiscordChatExporter.Core.Models
-
-namespace DiscordChatExporter.Core.Models
 {
-    // https://discordapp.com/developers/docs/resources/guild#guild-object
+    // https://discordapp.string.IsNullOrWhiteSpace(com/developers/docs/resources/guild#guild-object
 
     public partial class Guild
     {
@@ -10,11 +8,11 @@ namespace DiscordChatExporter.Core.Models
 
         public string Name { get; }
 
-        public string IconHash { get; }
+        public string? IconHash { get; }
 
         public string IconUrl { get; }
 
-        public Guild(string id, string name, string iconHash)
+        public Guild(string id, string name, string? iconHash)
         {
             Id = id;
             Name = name;
@@ -28,9 +26,9 @@ namespace DiscordChatExporter.Core.Models
 
     public partial class Guild
     {
-        public static string GetIconUrl(string id, string iconHash)
+        public static string GetIconUrl(string id, string? iconHash)
         {
-            return !iconHash.IsNullOrWhiteSpace()
+            return !string.IsNullOrWhiteSpace(iconHash)
                 ? $"https://cdn.discordapp.com/icons/{id}/{iconHash}.png"
                 : "https://cdn.discordapp.com/embed/avatars/0.png";
         }

DiscordChatExporter.Core.Models/Message.cs

@@ -19,7 +19,7 @@ namespace DiscordChatExporter.Core.Models
 
         public DateTimeOffset? EditedTimestamp { get; }
 
-        public string Content { get; }
+        public string? Content { get; }
 
         public IReadOnlyList<Attachment> Attachments { get; }
 
@@ -32,7 +32,7 @@ namespace DiscordChatExporter.Core.Models
         public bool IsPinned { get; }
 
         public Message(string id, string channelId, MessageType type, User author, DateTimeOffset timestamp,
-            DateTimeOffset? editedTimestamp, string content, IReadOnlyList<Attachment> attachments,
+            DateTimeOffset? editedTimestamp, string? content, IReadOnlyList<Attachment> attachments,
             IReadOnlyList<Embed> embeds, IReadOnlyList<Reaction> reactions, IReadOnlyList<User> mentionedUsers,
             bool isPinned)
         {
@@ -50,6 +50,6 @@ namespace DiscordChatExporter.Core.Models
             IsPinned = isPinned;
         }
 
-        public override string ToString() => Content;
+        public override string ToString() => Content ?? "<message without content>";
     }
 }

DiscordChatExporter.Core.Models/User.cs

@@ -1,5 +1,4 @@
 using System;
-using Tyrrrz.Extensions;
 
 namespace DiscordChatExporter.Core.Models
 {
@@ -15,13 +14,13 @@ namespace DiscordChatExporter.Core.Models
 
         public string FullName { get; }
 
-        public string AvatarHash { get; }
+        public string? AvatarHash { get; }
 
         public string AvatarUrl { get; }
 
         public bool IsBot { get; }
 
-        public User(string id, int discriminator, string name, string avatarHash, bool isBot)
+        public User(string id, int discriminator, string name, string? avatarHash, bool isBot)
         {
             Id = id;
             Discriminator = discriminator;
@@ -40,10 +39,10 @@ namespace DiscordChatExporter.Core.Models
     {
         public static string GetFullName(string name, int discriminator) => $"{name}#{discriminator:0000}";
 
-        public static string GetAvatarUrl(string id, int discriminator, string avatarHash)
+        public static string GetAvatarUrl(string id, int discriminator, string? avatarHash)
         {
             // Custom avatar
-            if (!avatarHash.IsNullOrWhiteSpace())
+            if (!string.IsNullOrWhiteSpace(avatarHash))
             {
                 // Animated
                 if (avatarHash.StartsWith("a_", StringComparison.Ordinal))

DiscordChatExporter.Core.Rendering/CsvChatLogRenderer.cs

@@ -96,7 +96,7 @@ namespace DiscordChatExporter.Core.Rendering
             await RenderFieldAsync(writer, FormatDate(message.Timestamp));
 
             // Content
-            await RenderFieldAsync(writer, FormatMarkdown(message.Content));
+            await RenderFieldAsync(writer, FormatMarkdown(message.Content ?? ""));
 
             // Attachments
             var formattedAttachments = message.Attachments.Select(a => a.Url).JoinToString(",");

DiscordChatExporter.Core.Rendering/DiscordChatExporter.Core.Rendering.csproj

@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>netcoreapp3.0</TargetFramework>
+    <Nullable>enable</Nullable>
   </PropertyGroup>
 
   <ItemGroup>

DiscordChatExporter.Core.Rendering/HtmlChatLogRenderer.cs

@@ -97,7 +97,7 @@ namespace DiscordChatExporter.Core.Rendering
             if (node is MultiLineCodeBlockNode multilineCodeBlockNode)
             {
                 // Set CSS class for syntax highlighting
-                var highlightCssClass = !multilineCodeBlockNode.Language.IsNullOrWhiteSpace()
+                var highlightCssClass = !string.IsNullOrWhiteSpace(multilineCodeBlockNode.Language)
                     ? $"language-{multilineCodeBlockNode.Language}"
                     : "nohighlight";
 
@@ -153,7 +153,7 @@ namespace DiscordChatExporter.Core.Rendering
                 // Extract message ID if the link points to a Discord message
                 var linkedMessageId = Regex.Match(linkNode.Url, "^https?://discordapp.com/channels/.*?/(\\d+)/?$").Groups[1].Value;
 
-                return linkedMessageId.IsNullOrWhiteSpace()
+                return string.IsNullOrWhiteSpace(linkedMessageId)
                     ? $"<a href=\"{Uri.EscapeUriString(linkNode.Url)}\">{HtmlEncode(linkNode.Title)}</a>"
                     : $"<a href=\"{Uri.EscapeUriString(linkNode.Url)}\" onclick=\"scrollToMessage(event, '{linkedMessageId}')\">{HtmlEncode(linkNode.Title)}</a>";
             }
@@ -165,7 +165,7 @@ namespace DiscordChatExporter.Core.Rendering
         private string FormatMarkdown(IReadOnlyList<Node> nodes, bool isTopLevel)
         {
             // Emojis are jumbo if all top-level nodes are emoji nodes or whitespace text nodes
-            var isJumbo = isTopLevel && nodes.All(n => n is EmojiNode || n is TextNode textNode && textNode.Text.IsNullOrWhiteSpace());
+            var isJumbo = isTopLevel && nodes.All(n => n is EmojiNode || n is TextNode textNode && string.IsNullOrWhiteSpace(textNode.Text));
 
             return nodes.Select(n => FormatMarkdown(n, isJumbo)).JoinToString("");
         }

DiscordChatExporter.Core.Rendering/PlainTextChatLogRenderer.cs

@@ -40,7 +40,7 @@ namespace DiscordChatExporter.Core.Rendering
                 return $"before {FormatDate(before.Value)}";
 
             // Neither
-            return null;
+            return "";
         }
 
         private string FormatMarkdown(Node node)
@@ -131,43 +131,43 @@ namespace DiscordChatExporter.Core.Rendering
                 await writer.WriteLineAsync("{Embed}");
 
                 // Author name
-                if (!(embed.Author?.Name).IsNullOrWhiteSpace())
+                if (!string.IsNullOrWhiteSpace(embed.Author?.Name))
                     await writer.WriteLineAsync(embed.Author?.Name);
 
                 // URL
-                if (!embed.Url.IsNullOrWhiteSpace())
+                if (!string.IsNullOrWhiteSpace(embed.Url))
                     await writer.WriteLineAsync(embed.Url);
 
                 // Title
-                if (!embed.Title.IsNullOrWhiteSpace())
+                if (!string.IsNullOrWhiteSpace(embed.Title))
                     await writer.WriteLineAsync(FormatMarkdown(embed.Title));
 
                 // Description
-                if (!embed.Description.IsNullOrWhiteSpace())
+                if (!string.IsNullOrWhiteSpace(embed.Description))
                     await writer.WriteLineAsync(FormatMarkdown(embed.Description));
 
                 // Fields
                 foreach (var field in embed.Fields)
                 {
                     // Name
-                    if (!field.Name.IsNullOrWhiteSpace())
+                    if (!string.IsNullOrWhiteSpace(field.Name))
                         await writer.WriteLineAsync(field.Name);
 
                     // Value
-                    if (!field.Value.IsNullOrWhiteSpace())
+                    if (!string.IsNullOrWhiteSpace(field.Value))
                         await writer.WriteLineAsync(field.Value);
                 }
 
                 // Thumbnail URL
-                if (!(embed.Thumbnail?.Url).IsNullOrWhiteSpace())
+                if (!string.IsNullOrWhiteSpace(embed.Thumbnail?.Url))
                     await writer.WriteLineAsync(embed.Thumbnail?.Url);
 
                 // Image URL
-                if (!(embed.Image?.Url).IsNullOrWhiteSpace())
+                if (!string.IsNullOrWhiteSpace(embed.Image?.Url))
                     await writer.WriteLineAsync(embed.Image?.Url);
 
                 // Footer text
-                if (!(embed.Footer?.Text).IsNullOrWhiteSpace())
+                if (!string.IsNullOrWhiteSpace(embed.Footer?.Text))
                     await writer.WriteLineAsync(embed.Footer?.Text);
 
                 await writer.WriteLineAsync();
@@ -201,6 +201,7 @@ namespace DiscordChatExporter.Core.Rendering
             await RenderMessageHeaderAsync(writer, message);
 
             // Content
+            if (!string.IsNullOrWhiteSpace(message.Content))
                 await writer.WriteLineAsync(FormatMarkdown(message.Content));
 
             // Separator

DiscordChatExporter.Core.Services/DataService.Parsers.cs

@@ -12,10 +12,10 @@ namespace DiscordChatExporter.Core.Services
     {
         private User ParseUser(JToken json)
         {
-            var id = json["id"].Value<string>();
+            var id = json["id"]!.Value<string>();
-            var discriminator = json["discriminator"].Value<int>();
+            var discriminator = json["discriminator"]!.Value<int>();
-            var name = json["username"].Value<string>();
+            var name = json["username"]!.Value<string>();
-            var avatarHash = json["avatar"].Value<string>();
+            var avatarHash = json["avatar"]!.Value<string>();
             var isBot = json["bot"]?.Value<bool>() ?? false;
 
             return new User(id, discriminator, name, avatarHash, isBot);
@@ -23,9 +23,9 @@ namespace DiscordChatExporter.Core.Services
 
         private Guild ParseGuild(JToken json)
         {
-            var id = json["id"].Value<string>();
+            var id = json["id"]!.Value<string>();
-            var name = json["name"].Value<string>();
+            var name = json["name"]!.Value<string>();
-            var iconHash = json["icon"].Value<string>();
+            var iconHash = json["icon"]!.Value<string>();
 
             return new Guild(id, name, iconHash);
         }
@@ -33,23 +33,23 @@ namespace DiscordChatExporter.Core.Services
         private Channel ParseChannel(JToken json)
         {
             // Get basic data
-            var id = json["id"].Value<string>();
+            var id = json["id"]!.Value<string>();
             var parentId = json["parent_id"]?.Value<string>();
-            var type = (ChannelType) json["type"].Value<int>();
+            var type = (ChannelType) json["type"]!.Value<int>();
             var topic = json["topic"]?.Value<string>();
 
             // Try to extract guild ID
             var guildId = json["guild_id"]?.Value<string>();
 
             // If the guild ID is blank, it's direct messages
-            if (guildId.IsNullOrWhiteSpace())
+            if (string.IsNullOrWhiteSpace(guildId))
                 guildId = Guild.DirectMessages.Id;
 
             // Try to extract name
             var name = json["name"]?.Value<string>();
 
             // If the name is blank, it's direct messages
-            if (name.IsNullOrWhiteSpace())
+            if (string.IsNullOrWhiteSpace(name))
                 name = json["recipients"].Select(ParseUser).Select(u => u.Name).JoinToString(", ");
 
             return new Channel(id, parentId, guildId, name, topic, type);
@@ -57,20 +57,20 @@ namespace DiscordChatExporter.Core.Services
 
         private Role ParseRole(JToken json)
         {
-            var id = json["id"].Value<string>();
+            var id = json["id"]!.Value<string>();
-            var name = json["name"].Value<string>();
+            var name = json["name"]!.Value<string>();
 
             return new Role(id, name);
         }
 
         private Attachment ParseAttachment(JToken json)
         {
-            var id = json["id"].Value<string>();
+            var id = json["id"]!.Value<string>();
-            var url = json["url"].Value<string>();
+            var url = json["url"]!.Value<string>();
             var width = json["width"]?.Value<int>();
             var height = json["height"]?.Value<int>();
-            var fileName = json["filename"].Value<string>();
+            var fileName = json["filename"]!.Value<string>();
-            var fileSizeBytes = json["size"].Value<long>();
+            var fileSizeBytes = json["size"]!.Value<long>();
 
             var fileSize = new FileSize(fileSizeBytes);
 
@@ -88,8 +88,8 @@ namespace DiscordChatExporter.Core.Services
 
         private EmbedField ParseEmbedField(JToken json)
         {
-            var name = json["name"].Value<string>();
+            var name = json["name"]!.Value<string>();
-            var value = json["value"].Value<string>();
+            var value = json["value"]!.Value<string>();
             var isInline = json["inline"]?.Value<bool>() ?? false;
 
             return new EmbedField(name, value, isInline);
@@ -106,7 +106,7 @@ namespace DiscordChatExporter.Core.Services
 
         private EmbedFooter ParseEmbedFooter(JToken json)
         {
-            var text = json["text"].Value<string>();
+            var text = json["text"]!.Value<string>();
             var iconUrl = json["icon_url"]?.Value<string>();
 
             return new EmbedFooter(text, iconUrl);
@@ -122,23 +122,23 @@ namespace DiscordChatExporter.Core.Services
 
             // Get color
             var color = json["color"] != null
-                ? Color.FromArgb(json["color"].Value<int>()).ResetAlpha()
+                ? Color.FromArgb(json["color"]!.Value<int>()).ResetAlpha()
                 : Color.FromArgb(79, 84, 92); // default color
 
             // Get author
-            var author = json["author"] != null ? ParseEmbedAuthor(json["author"]) : null;
+            var author = json["author"] != null ? ParseEmbedAuthor(json["author"]!) : null;
 
             // Get fields
-            var fields = json["fields"].EmptyIfNull().Select(ParseEmbedField).ToArray();
+            var fields = (json["fields"] ?? Enumerable.Empty<JToken>()).Select(ParseEmbedField).ToArray();
 
             // Get thumbnail
-            var thumbnail = json["thumbnail"] != null ? ParseEmbedImage(json["thumbnail"]) : null;
+            var thumbnail = json["thumbnail"] != null ? ParseEmbedImage(json["thumbnail"]!) : null;
 
             // Get image
-            var image = json["image"] != null ? ParseEmbedImage(json["image"]) : null;
+            var image = json["image"] != null ? ParseEmbedImage(json["image"]!) : null;
 
             // Get footer
-            var footer = json["footer"] != null ? ParseEmbedFooter(json["footer"]) : null;
+            var footer = json["footer"] != null ? ParseEmbedFooter(json["footer"]!) : null;
 
             return new Embed(title, url, timestamp, color, author, description, fields, thumbnail, image, footer);
         }
@@ -146,7 +146,7 @@ namespace DiscordChatExporter.Core.Services
         private Emoji ParseEmoji(JToken json)
         {
             var id = json["id"]?.Value<string>();
-            var name = json["name"]?.Value<string>();
+            var name = json["name"]!.Value<string>();
             var isAnimated = json["animated"]?.Value<bool>() ?? false;
 
             return new Emoji(id, name, isAnimated);
@@ -154,8 +154,8 @@ namespace DiscordChatExporter.Core.Services
 
         private Reaction ParseReaction(JToken json)
         {
-            var count = json["count"].Value<int>();
+            var count = json["count"]!.Value<int>();
-            var emoji = ParseEmoji(json["emoji"]);
+            var emoji = ParseEmoji(json["emoji"]!);
 
             return new Reaction(count, emoji);
         }
@@ -163,12 +163,12 @@ namespace DiscordChatExporter.Core.Services
         private Message ParseMessage(JToken json)
         {
             // Get basic data
-            var id = json["id"].Value<string>();
+            var id = json["id"]!.Value<string>();
-            var channelId = json["channel_id"].Value<string>();
+            var channelId = json["channel_id"]!.Value<string>();
-            var timestamp = json["timestamp"].Value<DateTime>().ToDateTimeOffset();
+            var timestamp = json["timestamp"]!.Value<DateTime>().ToDateTimeOffset();
             var editedTimestamp = json["edited_timestamp"]?.Value<DateTime?>()?.ToDateTimeOffset();
-            var content = json["content"].Value<string>();
+            var content = json["content"]!.Value<string>();
-            var type = (MessageType) json["type"].Value<int>();
+            var type = (MessageType) json["type"]!.Value<int>();
 
             // Workarounds for non-default types
             if (type == MessageType.RecipientAdd)
@@ -187,22 +187,22 @@ namespace DiscordChatExporter.Core.Services
                 content = "Joined the server.";
 
             // Get author
-            var author = ParseUser(json["author"]);
+            var author = ParseUser(json["author"]!);
 
             // Get attachments
-            var attachments = json["attachments"].EmptyIfNull().Select(ParseAttachment).ToArray();
+            var attachments = (json["attachments"] ?? Enumerable.Empty<JToken>()).Select(ParseAttachment).ToArray();
 
             // Get embeds
-            var embeds = json["embeds"].EmptyIfNull().Select(ParseEmbed).ToArray();
+            var embeds = (json["embeds"] ?? Enumerable.Empty<JToken>()).Select(ParseEmbed).ToArray();
 
             // Get reactions
-            var reactions = json["reactions"].EmptyIfNull().Select(ParseReaction).ToArray();
+            var reactions = (json["reactions"] ?? Enumerable.Empty<JToken>()).Select(ParseReaction).ToArray();
 
             // Get mentioned users
-            var mentionedUsers = json["mentions"].EmptyIfNull().Select(ParseUser).ToArray();
+            var mentionedUsers = (json["mentions"] ?? Enumerable.Empty<JToken>()).Select(ParseUser).ToArray();
 
             // Get whether this message is pinned
-            var isPinned = json["pinned"].Value<bool>();
+            var isPinned = json["pinned"]!.Value<bool>();
 
             return new Message(id, channelId, type, author, timestamp, editedTimestamp, content, attachments, embeds,
                 reactions, mentionedUsers, isPinned);

DiscordChatExporter.Core.Services/DataService.cs

@@ -45,7 +45,7 @@ namespace DiscordChatExporter.Core.Services
                     var value = parameter.SubstringAfter("=");
 
                     // Skip empty values
-                    if (value.IsNullOrWhiteSpace())
+                    if (string.IsNullOrWhiteSpace(value))
                         continue;
 
                     request.RequestUri = request.RequestUri.SetQueryParameter(key, value);
@@ -53,6 +53,7 @@ namespace DiscordChatExporter.Core.Services
 
                 // Get response
                 using var response = await _httpClient.SendAsync(request);
+
                 // Check status code
                 // We throw our own exception here because default one doesn't have status code
                 if (!response.IsSuccessStatusCode)
@@ -119,7 +120,7 @@ namespace DiscordChatExporter.Core.Services
         }
 
         public async Task<IReadOnlyList<Message>> GetChannelMessagesAsync(AuthToken token, string channelId,
-            DateTimeOffset? after = null, DateTimeOffset? before = null, IProgress<double> progress = null)
+            DateTimeOffset? after = null, DateTimeOffset? before = null, IProgress<double>? progress = null)
         {
             var result = new List<Message>();
 
@@ -211,7 +212,7 @@ namespace DiscordChatExporter.Core.Services
         }
 
         public async Task<ChatLog> GetChatLogAsync(AuthToken token, Guild guild, Channel channel,
-            DateTimeOffset? after = null, DateTimeOffset? before = null, IProgress<double> progress = null)
+            DateTimeOffset? after = null, DateTimeOffset? before = null, IProgress<double>? progress = null)
         {
             // Get messages
             var messages = await GetChannelMessagesAsync(token, channel.Id, after, before, progress);
@@ -223,19 +224,19 @@ namespace DiscordChatExporter.Core.Services
         }
 
         public async Task<ChatLog> GetChatLogAsync(AuthToken token, Channel channel,
-            DateTimeOffset? after = null, DateTimeOffset? before = null, IProgress<double> progress = null)
+            DateTimeOffset? after = null, DateTimeOffset? before = null, IProgress<double>? progress = null)
         {
             // Get guild
-            var guild = channel.GuildId == Guild.DirectMessages.Id
+            var guild = !string.IsNullOrWhiteSpace(channel.GuildId)
-                ? Guild.DirectMessages
+                ? await GetGuildAsync(token, channel.GuildId)
-                : await GetGuildAsync(token, channel.GuildId);
+                : Guild.DirectMessages;
 
             // Get the chat log
             return await GetChatLogAsync(token, guild, channel, after, before, progress);
         }
 
         public async Task<ChatLog> GetChatLogAsync(AuthToken token, string channelId,
-            DateTimeOffset? after = null, DateTimeOffset? before = null, IProgress<double> progress = null)
+            DateTimeOffset? after = null, DateTimeOffset? before = null, IProgress<double>? progress = null)
         {
             // Get channel
             var channel = await GetChannelAsync(token, channelId);

DiscordChatExporter.Core.Services/DiscordChatExporter.Core.Services.csproj

@@ -2,13 +2,14 @@
 
   <PropertyGroup>
     <TargetFramework>netcoreapp3.0</TargetFramework>
+    <Nullable>enable</Nullable>
   </PropertyGroup>
 
   <ItemGroup>
     <PackageReference Include="Failsafe" Version="1.1.0" />
-    <PackageReference Include="Newtonsoft.Json" Version="12.0.2" />
+    <PackageReference Include="Newtonsoft.Json" Version="12.0.3" />
-    <PackageReference Include="Onova" Version="2.4.5" />
+    <PackageReference Include="Onova" Version="2.5.1" />
-    <PackageReference Include="Tyrrrz.Extensions" Version="1.6.3" />
+    <PackageReference Include="Tyrrrz.Extensions" Version="1.6.5" />
     <PackageReference Include="Tyrrrz.Settings" Version="1.3.4" />
   </ItemGroup>
 

DiscordChatExporter.Core.Services/ExportService.cs

@@ -38,7 +38,7 @@ namespace DiscordChatExporter.Core.Services
         {
             // Create output directory
             var dirPath = Path.GetDirectoryName(filePath);
-            if (!dirPath.IsNullOrWhiteSpace())
+            if (!string.IsNullOrWhiteSpace(dirPath))
                 Directory.CreateDirectory(dirPath);
 
             // Render chat log to output file
@@ -74,7 +74,7 @@ namespace DiscordChatExporter.Core.Services
                     var partitionFilePath = $"{fileNameWithoutExt} [{partitionNumber} of {partitions.Length}]{fileExt}";
 
                     // Compose full file path
-                    if (!dirPath.IsNullOrWhiteSpace())
+                    if (!string.IsNullOrWhiteSpace(dirPath))
                         partitionFilePath = Path.Combine(dirPath, partitionFilePath);
 
                     // Export

DiscordChatExporter.Core.Services/Helpers/ExportHelper.cs

@@ -3,7 +3,6 @@ using System.IO;
 using System.Linq;
 using System.Text;
 using DiscordChatExporter.Core.Models;
-using Tyrrrz.Extensions;
 
 namespace DiscordChatExporter.Core.Services.Helpers
 {
@@ -12,7 +11,7 @@ namespace DiscordChatExporter.Core.Services.Helpers
         public static bool IsDirectoryPath(string path) =>
             path.Last() == Path.DirectorySeparatorChar ||
             path.Last() == Path.AltDirectorySeparatorChar ||
-            Path.GetExtension(path).IsNullOrWhiteSpace() && !File.Exists(path);
+            string.IsNullOrWhiteSpace(Path.GetExtension(path)) && !File.Exists(path);
 
         public static string GetDefaultExportFileName(ExportFormat format, Guild guild, Channel channel,
             DateTimeOffset? after = null, DateTimeOffset? before = null)

DiscordChatExporter.Core.Services/SettingsService.cs

@@ -9,8 +9,10 @@ namespace DiscordChatExporter.Core.Services
 
         public string DateFormat { get; set; } = "dd-MMM-yy hh:mm tt";
 
-        public AuthToken LastToken { get; set; }
+        public AuthToken? LastToken { get; set; }
+
         public ExportFormat LastExportFormat { get; set; } = ExportFormat.HtmlDark;
+
         public int? LastPartitionLimit { get; set; }
 
         public SettingsService()

DiscordChatExporter.Gui/App.xaml.cs

@@ -1,6 +1,16 @@
-namespace DiscordChatExporter.Gui
+using System;
+using System.Reflection;
+
+namespace DiscordChatExporter.Gui
 {
     public partial class App
     {
+        private static readonly Assembly Assembly = typeof(App).Assembly;
+
+        public static string Name => Assembly.GetName().Name!;
+
+        public static Version Version => Assembly.GetName().Version!;
+
+        public static string VersionString => Version.ToString(3);
     }
 }

DiscordChatExporter.Gui/Bootstrapper.cs

@@ -1,11 +1,14 @@
-using System.Windows;
+using DiscordChatExporter.Core.Services;
-using System.Windows.Threading;
-using DiscordChatExporter.Core.Services;
 using DiscordChatExporter.Gui.ViewModels;
 using DiscordChatExporter.Gui.ViewModels.Framework;
 using Stylet;
 using StyletIoC;
 
+#if !DEBUG
+using System.Windows;
+using System.Windows.Threading;
+#endif
+
 namespace DiscordChatExporter.Gui
 {
     public class Bootstrapper : Bootstrapper<RootViewModel>

DiscordChatExporter.Gui/Converters/DateTimeOffsetToDateTimeConverter.cs

@@ -14,7 +14,7 @@ namespace DiscordChatExporter.Gui.Converters
             if (value is DateTimeOffset dateTimeOffsetValue)
                 return dateTimeOffsetValue.DateTime;
 
-            return default;
+            return default(DateTime);
         }
 
         public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
@@ -22,7 +22,7 @@ namespace DiscordChatExporter.Gui.Converters
             if (value is DateTime dateTimeValue)
                 return new DateTimeOffset(dateTimeValue);
 
-            return default;
+            return default(DateTimeOffset);
         }
     }
 }

DiscordChatExporter.Gui/Converters/ExportFormatToStringConverter.cs

@@ -10,12 +10,12 @@ namespace DiscordChatExporter.Gui.Converters
     {
         public static ExportFormatToStringConverter Instance { get; } = new ExportFormatToStringConverter();
 
-        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
+        public object? Convert(object value, Type targetType, object parameter, CultureInfo culture)
         {
             if (value is ExportFormat exportFormatValue)
                 return exportFormatValue.GetDisplayName();
 
-            return default;
+            return default(string);
         }
 
         public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)

DiscordChatExporter.Gui/Converters/InverseBoolConverter.cs

@@ -14,7 +14,7 @@ namespace DiscordChatExporter.Gui.Converters
             if (value is bool boolValue)
                 return !boolValue;
 
-            return default;
+            return default(bool);
         }
 
         public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
@@ -22,7 +22,7 @@ namespace DiscordChatExporter.Gui.Converters
             if (value is bool boolValue)
                 return !boolValue;
 
-            return default;
+            return default(bool);
         }
     }
 }

DiscordChatExporter.Gui/DiscordChatExporter.Gui.csproj

@@ -7,6 +7,7 @@
     <Version>2.15</Version>
     <Company>Tyrrrz</Company>
     <Copyright>Copyright (c) Alexey Golub</Copyright>
+    <Nullable>enable</Nullable>
     <UseWPF>true</UseWPF>
     <ApplicationIcon>../favicon.ico</ApplicationIcon>
   </PropertyGroup>
@@ -19,11 +20,11 @@
     <PackageReference Include="Gress" Version="1.1.1" />
     <PackageReference Include="MaterialDesignColors" Version="1.2.0" />
     <PackageReference Include="MaterialDesignThemes" Version="2.6.0" />
-    <PackageReference Include="Microsoft.Xaml.Behaviors.Wpf" Version="1.0.1" />
+    <PackageReference Include="Microsoft.Xaml.Behaviors.Wpf" Version="1.1.3" />
     <PackageReference Include="Ookii.Dialogs.Wpf" Version="1.1.0" />
     <PackageReference Include="PropertyChanged.Fody" Version="3.1.3" />
     <PackageReference Include="Stylet" Version="1.3.0" />
-    <PackageReference Include="Tyrrrz.Extensions" Version="1.6.3" />
+    <PackageReference Include="Tyrrrz.Extensions" Version="1.6.5" />
   </ItemGroup>
 
   <ItemGroup>

DiscordChatExporter.Gui/Services/UpdateService.cs

@@ -1,6 +1,5 @@
 using System;
 using System.Threading.Tasks;
-using DiscordChatExporter.Core.Services;
 using Onova;
 using Onova.Exceptions;
 using Onova.Services;
@@ -13,10 +12,10 @@ namespace DiscordChatExporter.Gui.Services
             new GithubPackageResolver("Tyrrrz", "DiscordChatExporter", "DiscordChatExporter.zip"),
             new ZipPackageExtractor());
 
-        private Version _updateVersion;
+        private Version? _updateVersion;
         private bool _updaterLaunched;
 
-        public async Task<Version> CheckForUpdatesAsync()
+        public async Task<Version?> CheckForUpdatesAsync()
         {
             var check = await _updateManager.CheckForUpdatesAsync();
             return check.CanUpdate ? check.LastVersion : null;

DiscordChatExporter.Gui/ViewModels/Components/ChannelViewModel.cs

@@ -7,7 +7,7 @@ namespace DiscordChatExporter.Gui.ViewModels.Components
     {
         public Channel Model { get; set; }
 
-        public string Category { get; set; }
+        public string? Category { get; set; }
     }
 
     public partial class ChannelViewModel

DiscordChatExporter.Gui/ViewModels/Dialogs/ExportSetupViewModel.cs

@@ -6,7 +6,6 @@ using DiscordChatExporter.Core.Services;
 using DiscordChatExporter.Core.Services.Helpers;
 using DiscordChatExporter.Gui.ViewModels.Components;
 using DiscordChatExporter.Gui.ViewModels.Framework;
-using Tyrrrz.Extensions;
 
 namespace DiscordChatExporter.Gui.ViewModels.Dialogs
 {
@@ -21,12 +20,12 @@ namespace DiscordChatExporter.Gui.ViewModels.Dialogs
 
         public bool IsSingleChannel => Channels.Count == 1;
 
-        public string OutputPath { get; set; }
+        public string? OutputPath { get; set; }
 
         public IReadOnlyList<ExportFormat> AvailableFormats =>
             Enum.GetValues(typeof(ExportFormat)).Cast<ExportFormat>().ToArray();
 
-        public ExportFormat SelectedFormat { get; set; } = ExportFormat.HtmlDark;
+        public ExportFormat SelectedFormat { get; set; }
 
         public DateTimeOffset? After { get; set; }
 
@@ -38,11 +37,6 @@ namespace DiscordChatExporter.Gui.ViewModels.Dialogs
         {
             _dialogManager = dialogManager;
             _settingsService = settingsService;
-        }
-
-        protected override void OnViewLoaded()
-        {
-            base.OnViewLoaded();
 
             // Persist preferences
             SelectedFormat = _settingsService.LastExportFormat;
@@ -85,7 +79,7 @@ namespace DiscordChatExporter.Gui.ViewModels.Dialogs
             }
 
             // If canceled - return
-            if (OutputPath.IsNullOrWhiteSpace())
+            if (string.IsNullOrWhiteSpace(OutputPath))
                 return;
 
             // Close dialog

DiscordChatExporter.Gui/ViewModels/Framework/DialogManager.cs

@@ -1,4 +1,5 @@
-using System.IO;
+using System;
+using System.IO;
 using System.Threading.Tasks;
 using MaterialDesignThemes.Wpf;
 using Microsoft.Win32;
@@ -22,10 +23,10 @@ namespace DiscordChatExporter.Gui.ViewModels.Framework
             var view = _viewManager.CreateAndBindViewForModelIfNecessary(dialogScreen);
 
             // Set up event routing that will close the view when called from viewmodel
-            void OnDialogOpened(object sender, DialogOpenedEventArgs openArgs)
+            void OnDialogOpened(object? sender, DialogOpenedEventArgs openArgs)
             {
                 // Delegate to close the dialog and unregister event handler
-                void OnScreenClosed(object o, CloseEventArgs closeArgs)
+                void OnScreenClosed(object? o, EventArgs closeArgs)
                 {
                     openArgs.Session.Close();
                     dialogScreen.Closed -= OnScreenClosed;
@@ -41,7 +42,7 @@ namespace DiscordChatExporter.Gui.ViewModels.Framework
             return dialogScreen.DialogResult;
         }
 
-        public string PromptSaveFilePath(string filter = "All files|*.*", string defaultFilePath = "")
+        public string? PromptSaveFilePath(string filter = "All files|*.*", string defaultFilePath = "")
         {
             // Create dialog
             var dialog = new SaveFileDialog
@@ -56,7 +57,7 @@ namespace DiscordChatExporter.Gui.ViewModels.Framework
             return dialog.ShowDialog() == true ? dialog.FileName : null;
         }
 
-        public string PromptDirectoryPath(string defaultDirPath = "")
+        public string? PromptDirectoryPath(string defaultDirPath = "")
         {
             // Create dialog
             var dialog = new VistaFolderBrowserDialog

DiscordChatExporter.Gui/ViewModels/Framework/DialogScreen.cs

@@ -1,22 +1,18 @@
-using Stylet;
+using System;
+using Stylet;
 
 namespace DiscordChatExporter.Gui.ViewModels.Framework
 {
-    public abstract class DialogScreen<T> : Screen
+    public abstract class DialogScreen<T> : PropertyChangedBase
     {
         public T DialogResult { get; private set; }
 
+        public event EventHandler? Closed;
+
         public void Close(T dialogResult = default)
         {
-            // Set the result
             DialogResult = dialogResult;
-
+            Closed?.Invoke(this, EventArgs.Empty);
-            // If there is a parent - ask them to close this dialog
-            if (Parent != null)
-                RequestClose(Equals(dialogResult, default(T)));
-            // Otherwise close ourselves
-            else
-                ((IScreenState) this).Close();
         }
     }
 

DiscordChatExporter.Gui/ViewModels/Framework/Extensions.cs

@@ -7,8 +7,7 @@ namespace DiscordChatExporter.Gui.ViewModels.Framework
 {
     public static class Extensions
     {
-        public static ChannelViewModel CreateChannelViewModel(this IViewModelFactory factory, Channel model,
+        public static ChannelViewModel CreateChannelViewModel(this IViewModelFactory factory, Channel model, string? category = null)
-            string category = null)
         {
             var viewModel = factory.CreateChannelViewModel();
             viewModel.Model = model;

DiscordChatExporter.Gui/ViewModels/RootViewModel.cs

@@ -3,7 +3,6 @@ using System.Collections.Generic;
 using System.IO;
 using System.Linq;
 using System.Net;
-using System.Reflection;
 using System.Threading.Tasks;
 using DiscordChatExporter.Core.Models;
 using DiscordChatExporter.Core.Services;
@@ -38,13 +37,13 @@ namespace DiscordChatExporter.Gui.ViewModels
 
         public bool IsBotToken { get; set; }
 
-        public string TokenValue { get; set; }
+        public string? TokenValue { get; set; }
 
-        public IReadOnlyList<GuildViewModel> AvailableGuilds { get; private set; }
+        public IReadOnlyList<GuildViewModel>? AvailableGuilds { get; private set; }
 
-        public GuildViewModel SelectedGuild { get; set; }
+        public GuildViewModel? SelectedGuild { get; set; }
 
-        public IReadOnlyList<ChannelViewModel> SelectedChannels { get; set; }
+        public IReadOnlyList<ChannelViewModel>? SelectedChannels { get; set; }
 
         public RootViewModel(IViewModelFactory viewModelFactory, DialogManager dialogManager,
             SettingsService settingsService, UpdateService updateService, DataService dataService,
@@ -58,8 +57,7 @@ namespace DiscordChatExporter.Gui.ViewModels
             _exportService = exportService;
 
             // Set title
-            var version = Assembly.GetExecutingAssembly().GetName().Version.ToString(3);
+            DisplayName = $"{App.Name} v{App.VersionString}";
-            DisplayName = $"DiscordChatExporter v{version}";
 
             // Update busy state when progress manager changes
             ProgressManager.Bind(o => o.IsActive, (sender, args) => IsBusy = ProgressManager.IsActive);
@@ -83,7 +81,7 @@ namespace DiscordChatExporter.Gui.ViewModels
                     return;
 
                 // Notify user of an update and prepare it
-                Notifications.Enqueue($"Downloading update to DiscordChatExporter v{updateVersion}...");
+                Notifications.Enqueue($"Downloading update to {App.Name} v{updateVersion}...");
                 await _updateService.PrepareUpdateAsync(updateVersion);
 
                 // Prompt user to install update (otherwise install it when application exits)
@@ -140,7 +138,7 @@ namespace DiscordChatExporter.Gui.ViewModels
             await _dialogManager.ShowDialogAsync(dialog);
         }
 
-        public bool CanPopulateGuildsAndChannels => !IsBusy && !TokenValue.IsNullOrWhiteSpace();
+        public bool CanPopulateGuildsAndChannels => !IsBusy && !string.IsNullOrWhiteSpace(TokenValue);
 
         public async void PopulateGuildsAndChannels()
         {
@@ -150,7 +148,7 @@ namespace DiscordChatExporter.Gui.ViewModels
             try
             {
                 // Sanitize token
-                TokenValue = TokenValue.Trim('"');
+                TokenValue = TokenValue!.Trim('"');
 
                 // Create token
                 var token = new AuthToken(
@@ -253,15 +251,15 @@ namespace DiscordChatExporter.Gui.ViewModels
             }
         }
 
-        public bool CanExportChannels => !IsBusy && !SelectedChannels.IsNullOrEmpty();
+        public bool CanExportChannels => !IsBusy && SelectedGuild != null && SelectedChannels != null && SelectedChannels.Any();
 
         public async void ExportChannels()
         {
             // Get last used token
-            var token = _settingsService.LastToken;
+            var token = _settingsService.LastToken!;
 
             // Create dialog
-            var dialog = _viewModelFactory.CreateExportSetupViewModel(SelectedGuild, SelectedChannels);
+            var dialog = _viewModelFactory.CreateExportSetupViewModel(SelectedGuild!, SelectedChannels!);
 
             // Show dialog, if canceled - return
             if (await _dialogManager.ShowDialogAsync(dialog) != true)
@@ -281,7 +279,7 @@ namespace DiscordChatExporter.Gui.ViewModels
                 try
                 {
                     // Generate file path if necessary
-                    var filePath = dialog.OutputPath;
+                    var filePath = dialog.OutputPath!;
                     if (ExportHelper.IsDirectoryPath(filePath))
                     {
                         // Generate default file name