Discord.Net 创建 Webhook 并获取其 URL

问：

我目前正在制作一个机器人，我希望它创建一个 webhook 并获取其 URL，以便它可以向它发送消息

var webhook = await (chan as ITextChannel).CreateWebhookAsync("Webhook");                                   
await SendWHMsg(webhook.Url, WebhookName, WebhookAvatar, msg); 

（WebhookName、WebhookAvatar 和 msg 已经定义了变量）

发送WHMsg：

    private async Task SendWHMsg(string webhookUrl, string webhookName, string avatarUrl, string message)
    {
            using (HttpClient client = new HttpClient())
            {
                    var payload = new
                    {
                            username = webhookName,
                            avatar_url = avatarUrl,
                            content = message
                    };

                    string jsonPayload = Newtonsoft.Json.JsonConvert.SerializeObject(payload);
                    var content = new StringContent(jsonPayload, Encoding.UTF8, "application/json");

                    await client.PostAsync(webhookUrl, content);

            }
    }