View Source ExTDLib.Method.CheckChatUsername (ExTDLib v0.0.4)

Checks whether a username can be set for a chat. Returns object_ptr<CheckChatUsernameResult>.

NameTypeDescription
chat_idstringChat identifier; must be identifier of a supergroup chat, or a channel chat, or a private chat with self, or 0 if the chat is being created.
usernamestringUsername to be checked.

More details on telegram's documentation.