This is a simple test through WebHook. if you'd like to webhook test quickly using LINE Developers.NET, please following below description step by step.

• Messaging API → issue and copy to Channel access token (long-lived)

1. download line webhook sample project
2. Visual Studio → open line webhook sample project
3. modify to your Channel access token in LineController constructor

• LineController.cs

public LineController()
{
    _client = new LineMessagingClient("your channel access token"); //here
}

4. Visual Studio → F5
5. take a note or remember of your localhost address and callback url.

• ex) localhost : https://localhost:7250, callback url: /line/callback

need to follow the below process for LINE Messenger Serever call directly your local webhook address.

• ngrok download

1. run ngrok with your local host in console

   ngrok http https://localhost:7250/

2. copy created host via ngrok

1. LINE Developers Console → Messaging API → Webhook settings
2. Use webhhook ✔
3. Webhook URL → Edit → ngrok host + callback url → Update → Verifiy → Success

If you type some text on your channel, you'll get the message from LINE messenger which is set the webhook.