Some fixes & add support for `default_sort_order`

src/Discord.Net.Core/Entities/Channels/ForumChannelProperties.cs

@@ -52,4 +52,9 @@ public class ForumChannelProperties : TextChannelProperties
     /// Gets or sets a new default reaction emoji in this forum channel.
     /// </summary>
     public Optional<IEmote> DefaultReactionEmoji { get; set; }
+
+    /// <summary>
+    /// Gets or sets the rule used to order posts in forum channels.
+    /// </summary>
+    public Optional<ForumSortOrder> DefaultSortOrder { get; set; }
 }

src/Discord.Net.Core/Entities/Channels/ForumSortOrder.cs

@@ -0,0 +1,17 @@
+namespace Discord;
+
+/// <summary>
+/// Defines the rule used to order posts in forum channels.
+/// </summary>
+public enum ForumSortOrder
+{
+    /// <summary>
+    ///     Sort forum posts by activity.
+    /// </summary>
+    LatestActivity = 0,
+
+    /// <summary>
+    ///     Sort forum posts by creation time (from most recent to oldest).
+    /// </summary>
+    CreationDate = 1
+}

src/Discord.Net.Core/Entities/Channels/IForumChannel.cs

@@ -62,6 +62,14 @@ namespace Discord
         /// </remarks>
         IEmote DefaultReactionEmoji { get; }
 
+        /// <summary>
+        /// Gets or sets the rule used to order posts in forum channels.
+        /// </summary>
+        /// <remarks>
+        /// Defaults to null, which indicates a preferred sort order hasn't been set
+        /// </remarks>
+        ForumSortOrder? DefaultSortOrder { get; }
+
         /// <summary>
         ///     Modifies this forum channel.
         /// </summary>

src/Discord.Net.Rest/API/Common/Channel.cs

@@ -83,7 +83,11 @@ namespace Discord.API
         [JsonProperty("flags")]
         public Optional<ChannelFlags> Flags { get; set; }
 
+        [JsonProperty("default_sort_order")]
+        public Optional<ForumSortOrder?> DefaultSortOrder { get; set; }
+
         [JsonProperty("default_reaction_emoji")]
         public Optional<ForumReactionEmoji> DefaultReactionEmoji { get; set; }
+
     }
 }

src/Discord.Net.Rest/API/Common/ForumReactionEmoji.cs

@@ -5,7 +5,7 @@ namespace Discord.API;
 public class ForumReactionEmoji
 {
     [JsonProperty("emoji_id")]
-    public Optional<ulong?> EmojiId { get; set; }
+    public ulong? EmojiId { get; set; }
 
     [JsonProperty("emoji_name")]
     public Optional<string> EmojiName { get; set; }

src/Discord.Net.Rest/API/Rest/CreateGuildChannelParams.cs

@@ -39,6 +39,8 @@ namespace Discord.API.Rest
         public Optional<int> ThreadRateLimitPerUser { get; set; }
         [JsonProperty("available_tags")]
         public Optional<ModifyForumTagParams[]> AvailableTags { get; set; }
+        [JsonProperty("default_sort_order")]
+        public Optional<ForumSortOrder?> DefaultSortOrder { get; set; }
 
         public CreateGuildChannelParams(string name, ChannelType type)
         {

src/Discord.Net.Rest/API/Rest/ModifyForumChannelParams.cs

@@ -17,4 +17,7 @@ internal class ModifyForumChannelParams : ModifyTextChannelParams
 
     [JsonProperty("default_reaction_emoji")]
     public Optional<ModifyForumReactionEmojiParams> DefaultReactionEmoji { get; set; }
+
+    [JsonProperty("default_sort_order")]
+    public Optional<ForumSortOrder> DefaultSortOrder { get; set; }
 }

src/Discord.Net.Rest/Entities/Channels/ForumHelper.cs

@@ -52,7 +52,8 @@ internal static class ForumHelper
                     EmojiName = args.DefaultReactionEmoji.Value is Emoji emoji ?
                         emoji.Name : Optional<string>.Unspecified
                 }
-                : Optional<ModifyForumReactionEmojiParams>.Unspecified
+                : Optional<ModifyForumReactionEmojiParams>.Unspecified,
+            DefaultSortOrder = args.DefaultSortOrder
         };
         return await client.ApiClient.ModifyGuildChannelAsync(channel.Id, apiArgs, options).ConfigureAwait(false);
     }

src/Discord.Net.Rest/Entities/Channels/RestForumChannel.cs

@@ -38,6 +38,9 @@ namespace Discord.Rest
         /// <inheritdoc/>
         public IEmote DefaultReactionEmoji { get; private set; }
 
+        /// <inheritdoc/>
+        public ForumSortOrder? DefaultSortOrder { get; private set; }
+
         /// <inheritdoc/>
         public string Mention => MentionUtils.MentionChannel(Id);
 
@@ -67,14 +70,16 @@ namespace Discord.Rest
             if(model.SlowMode.IsSpecified)
                 ThreadCreationInterval = model.SlowMode.Value;
 
+            DefaultSortOrder = model.DefaultSortOrder.GetValueOrDefault();
+
             Tags = model.ForumTags.GetValueOrDefault(Array.Empty<API.ForumTags>()).Select(
                 x => new ForumTag(x.Id, x.Name, x.EmojiId.GetValueOrDefault(null), x.EmojiName.GetValueOrDefault(), x.Moderated)
             ).ToImmutableArray();
 
-            if (model.DefaultReactionEmoji.IsSpecified)
+            if (model.DefaultReactionEmoji.IsSpecified && model.DefaultReactionEmoji.Value is not null)
             {
-                if (model.DefaultReactionEmoji.Value.EmojiId.IsSpecified && model.DefaultReactionEmoji.Value.EmojiId.Value != 0)
-                    DefaultReactionEmoji = new Emote(model.DefaultReactionEmoji.Value.EmojiId.Value.GetValueOrDefault(), null, false);
+                if (model.DefaultReactionEmoji.Value.EmojiId.HasValue && model.DefaultReactionEmoji.Value.EmojiId.Value != 0)
+                    DefaultReactionEmoji = new Emote(model.DefaultReactionEmoji.Value.EmojiId.GetValueOrDefault(), null, false);
                 else if (model.DefaultReactionEmoji.Value.EmojiName.IsSpecified)
                     DefaultReactionEmoji = new Emoji(model.DefaultReactionEmoji.Value.EmojiName.Value);
                 else

src/Discord.Net.Rest/Entities/Guilds/GuildHelper.cs

@@ -364,7 +364,7 @@ namespace Discord.Rest
                     }).ToArray()
                     : Optional.Create<API.Overwrite[]>(),
                 SlowModeInterval = props.ThreadCreationInterval,
-                AvailableTags = props.Tags.GetValueOrDefault().Select(
+                AvailableTags = props.Tags.GetValueOrDefault(Array.Empty<ForumTagProperties>()).Select(
                     x => new ModifyForumTagParams
                     {
                         Id = x.Id,
@@ -390,7 +390,8 @@ namespace Discord.Rest
                 CategoryId = props.CategoryId,
                 IsNsfw = props.IsNsfw,
                 Topic = props.Topic,
-                DefaultAutoArchiveDuration = props.AutoArchiveDuration
+                DefaultAutoArchiveDuration = props.AutoArchiveDuration,
+                DefaultSortOrder = props.DefaultSortOrder.GetValueOrDefault(ForumSortOrder.LatestActivity)
             };
 
             var model = await client.ApiClient.CreateGuildChannelAsync(guild.Id, args, options).ConfigureAwait(false);

src/Discord.Net.WebSocket/Entities/Channels/SocketForumChannel.cs

@@ -42,6 +42,9 @@ namespace Discord.WebSocket
         /// <inheritdoc/>
         public IEmote DefaultReactionEmoji { get; private set; }
 
+        /// <inheritdoc/>
+        public ForumSortOrder? DefaultSortOrder { get; private set; }
+
         /// <summary>
         ///     Gets the parent (category) of this channel in the guild's channel list.
         /// </summary>
@@ -73,14 +76,16 @@ namespace Discord.WebSocket
             if (model.SlowMode.IsSpecified)
                 ThreadCreationInterval = model.SlowMode.Value;
 
+            DefaultSortOrder = model.DefaultSortOrder.GetValueOrDefault();
+
             Tags = model.ForumTags.GetValueOrDefault(Array.Empty<API.ForumTags>()).Select(
                 x => new ForumTag(x.Id, x.Name, x.EmojiId.GetValueOrDefault(null), x.EmojiName.GetValueOrDefault(), x.Moderated)
             ).ToImmutableArray();
 
-            if (model.DefaultReactionEmoji.IsSpecified)
+            if (model.DefaultReactionEmoji.IsSpecified && model.DefaultReactionEmoji.Value is not null)
             {
-                if (model.DefaultReactionEmoji.Value.EmojiId.IsSpecified && model.DefaultReactionEmoji.Value.EmojiId.Value != 0)
-                    DefaultReactionEmoji = new Emote(model.DefaultReactionEmoji.Value.EmojiId.Value.GetValueOrDefault(), null, false);
+                if (model.DefaultReactionEmoji.Value.EmojiId.HasValue && model.DefaultReactionEmoji.Value.EmojiId.Value != 0)
+                    DefaultReactionEmoji = new Emote(model.DefaultReactionEmoji.Value.EmojiId.GetValueOrDefault(), null, false);
                 else if (model.DefaultReactionEmoji.Value.EmojiName.IsSpecified)
                     DefaultReactionEmoji = new Emoji(model.DefaultReactionEmoji.Value.EmojiName.Value);
                 else