Basic Operations Questions

How should I safely check a type?

In Discord.NET, the idea of polymorphism is used throughout. You may need to cast the object as a certain type before you can perform any action. There are several ways to cast, with direct casting (Type)type being the the least recommended, as it can throw an InvalidCastException when the object isn't the desired type. Please refer to this post for more details.

A good and safe casting example:

public async Task MessageReceivedHandler(SocketMessage msg)
{
   // Option 1:
   // Using the `as` keyword, which will return `null` if the object isn't the desired type.
   var usermsg = msg as SocketUserMessage;
   // We bail when the message isn't the desired type.
   if (msg == null) return;
   
   // Option 2:
   // Using the `is` keyword to cast (C#7 or above only)
   if (msg is SocketUserMessage usermsg) 
   {
      // Do things
   }
}

How do I send a message?

Any implementation of IMessageChannel has a SendMessageAsync method. Using the client, you can get an appropriate channel (GetChannel(id)) to send a message to. Remember, when using Discord.NET, polymorphism is a common recurring theme. This means an object may take in many shapes or form, which means casting is your friend. You should attempt to cast the channel as an IMessageChannel or any other entity that implements it to be able to message.

How can I tell if a message is from X, Y, Z?

You may check message channel type.

A Text channel (ITextChannel) is a message channel from a Guild.
A DM channel (IDMChannel) is a message channel from a DM.
A Group channel (IGroupChannel) is a message channel from a Group (this is rarely used, due to the bot's inability to join a group).
A Private channel (IPrivateChannel) is a DM or a Group.
A Message channel (IMessageChannel) is all of the above.

How do I add hyperlink text to an embed?

Embeds can use standard markdown in the Description as well as in field values. With that in mind, links can be added using the following format [text](link).

How do I add reactions to a message?

Any entities that implement IUserMessage has an AddReactionAsync method. This method expects an IEmote as a parameter. In Discord.Net, an Emote represents a server custom emote, while an Emoji is a Unicode emoji (standard emoji). Both Emoji and Emote implement IEmote and are valid options.

// bail if the message is not a user one (system messages cannot have reactions)
var usermsg = msg as IUserMessage;
if (usermsg == null) return;

// standard Unicode emojis
Emoji emoji = new Emoji("👍");
// or
// Emoji emoji = new Emoji("\u23F8");

// custom guild emotes
Emote emote = Emote.Parse("<:dotnet:232902710280716288>");  
// using Emote.TryParse may be safer in regards to errors being thrown;
// please note that the method does not verify if the emote exists,
// it simply creates the Emote object for you.

// add the reaction to the message
await usermsg.AddReactionAsync(emoji); 
await usermsg.AddReactionAsync(emote);

Why am I getting so many preemptive rate limits when I try to add more than one reactions?

This is due to how .NET parses the HTML header, mistreating 0.25sec/action to 1sec. This casues the lib to throw preemptive rate limit more frequently than it should for methods such as adding reactions.

Can I opt-out of preemptive rate limits?

Unfortunately, not at the moment. See #401.

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