Console.WriteLine($"We are logged-in as {user.username ?? user.first_name + " " + user.last_name} (id {user.id})");
}
```
When run, this will prompt you interactively for your App **api_id** and **api_hash** (that you obtain through Telegram's [API development tools](https://my.telegram.org/apps) page) and try to connect to Telegram servers.
Then it will attempt to sign-in as a user for which you must enter the **phone_number** and the **verification_code** that will be sent to this user (for example through SMS or another Telegram client app the user is connected to).
If the verification succeeds but the phone number is unknown to Telegram, the user might be prompted to sign-up (accepting the Terms of Service) and enter their **first_name** and **last_name**.
And that's it, you now have access to the [full range of Telegram services](https://corefork.telegram.org/methods), mainly through calls to `await client.Some_TL_Method(...)`
If you run this program again, you will notice that only **api_id** and **api_hash** are requested, the other prompts are gone and you are automatically logged-on and ready to go.
This is because WTelegramClient saves (typically in the encrypted file **bin\WTelegram.session**) its state and the authentication keys that were negociated with Telegram so that you needn't sign-in again every time.
That file path is configurable, and under various circumstances (changing user or server address) you may want to change it or simply delete the existing session file in order to restart the authentification process.
# Non-interactive configuration
Your next step will probably be to provide a configuration to the client so that the required elements (in bold above) are not prompted through the Console but answered by your program.
Another simple approach is to pass `Environment.GetEnvironmentVariable` as the config callback and define the configuration items as environment variables.
Finally, if you want to redirect the library logs to your logger instead of the Console, you can install a delegate in the `WTelegram.Helpers.Log` static property.
Its `int` argument is the log severity, compatible with the classic [LogLevel enum](https://docs.microsoft.com/en-us/dotnet/api/microsoft.extensions.logging.loglevel)
>ℹ️ The Telegram API makes extensive usage of base and derived classes, so be ready to use the various syntaxes C# offer to check/cast base classes into the more useful derived classes (`is`, `as`, `case DerivedType` )
All the Telegram API classes/methods are fully documented through Intellisense: Place your mouse over a class/method name, or start typing the call arguments to see a tooltip display their description, the list of derived classes and a web link to the official API page.
The Telegram [API object classes](https://corefork.telegram.org/schema) are defined in the `TL` namespace, and the [API functions](https://corefork.telegram.org/methods) are available as async methods of `Client`.
Below is an example of calling the [messages.getAllChats](https://corefork.telegram.org/method/messages.getAllChats) API function and enumerating the various groups/channels the user is in, and then using `client.SendMessageAsync` helper function to easily send a message:
➡️ You can find more useful code snippets in [EXAMPLES.md](https://github.com/wiz0u/WTelegramClient/blob/master/EXAMPLES.md) and in the [Examples subdirectory](https://github.com/wiz0u/WTelegramClient/tree/master/Examples).
-`Channel` : A (large or public) chat group *(sometimes called supergroup)* or a broadcast channel (the `broadcast` flag differenciate those)
-`Chat` : A private simple chat group with less than 200 members (it may be migrated to a supergroup `Channel` with a new ID when it gets bigger or public, in which case the old `Chat` will still exist but be `deactivated`)
- chats : In plural or general meaning, it means either `Chat` or `Channel`
- Access Hash : For more security, Telegram requires you to provide the specific `access_hash` for users, chats, and other resources before interacting with them (not required for a simple `Chat`). This acts like a proof you are entitled to access it. You obtain this hash when you first gain access to a resource, or by querying the API or if there is an update about this resource. You should save this hash if you want to access that resource later.
The Client class also offers an `Update` event that is triggered when Telegram servers sends unsollicited Updates or notifications/information/status/service messages, independently of your API requests. See [Examples/Program_ListenUpdates.cs](https://github.com/wiz0u/WTelegramClient/blob/master/Examples/Program_ListenUpdates.cs)
An invalid API request can result in a `RpcException` being raised, reflecting the [error code and status text](https://revgram.github.io/errors.html) of the problem.
The other configuration items that you can override include: **session_pathname, server_address, device_model, system_version, app_version, system_lang_code, lang_pack, lang_code, user_id**
Optional API parameters have a default value of `null` when unset. Passing `null` for a required string/array is the same as *empty* (0-length). Required API parameters/fields can sometimes be set to 0 or `null` when unused (check API documentation or experiment).
Please don't use this library for Spam or Scam. Respect Telegram [Terms of Service](https://telegram.org/tos) as well as the [API Terms of Service](https://core.telegram.org/api/terms) or you might get banned from Telegram servers.
You can also check our [📖 Frequently Asked Questions](https://github.com/wiz0u/WTelegramClient/blob/master/FAQ.md) for more help and troubleshooting guide.
