After installing WTelegramClient through Nuget, your first Console program will be as simple as:
```csharp
static Task Main(string[] _)
{
using var client = new WTelegram.Client();
await client.ConnectAsync();
var user = await client.UserAuthIfNeeded();
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**.
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.
For that you need to write a method that will provide the answer, and pass it on the constructor:
```csharp
static string Config(string what)
{
if (what == "api_id") return "YOUR_API_ID";
if (what == "api_hash") return "YOUR_API_HASH";
if (what == "phone_number") return "+12025550156";
if (what == "verification_code") { Console.Write("Code: "); return Console.ReadLine(); }
if (what == "first_name") return "John"; // if sign-up is required
if (what == "last_name") return "Doe"; // if sign-up is required
return null;
}
...
using var client = new WTelegram.Client(Config);
```
There are other configuration items that are queried to your method but returning `null` let WTelegramClient choose a default adequate value.
The constructor also takes another optional delegate parameter that will be called for any other Update and other information/status/service messages that Telegram sends unsollicited, independently of your API requests.
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)
:information_source: 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` )
To find which derived classes are available for a given base class, the fastest is to check our [TL.Schema.cs](src/TL.Schema.cs) source file as they are listed in groups.
The Telegram [API object classes](https://core.telegram.org/schema) are defined in the `TL` namespace, and the request classes ([API functions](https://core.telegram.org/methods)) usable with `client.CallAsync` are under the `TL.Fn` static class.
Below is an example of calling the [messages.getAllChats](https://core.telegram.org/method/messages.getAllChats) API function and enumerating the various groups/channels the user is in:
An invalid API request can result in a RpcException being raised, reflecting the [error code and status text](https://core.telegram.org/api/errors) of the problem.
Beyond CallAsync, the Client class offers a few other methods to simplify the sending of files, medias or messages.
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**
