C# Decoding long Base64 Strings

Question

I am using Unity Free + NodeJS to code a small project with my mates.

NodeJs for the Server, and Unity for the Clients.

If you entered valid login data, the Server will return a jwt using njwt, which can be decoded using various online tools, and with c#.

But, this Line: byte[] _dec = Convert.FromBase64String(part); returns no error, but also prevents execution of more code. And I don't know why.

Here are more samples to understand what's going on.

LoginMenu.cs

ws.OnMessage += (sender, e) => {
    JObject res = JObject.Parse(e.Data);

    switch ((string)res["type"])
    {
        // If we get a token from the server
        // login was successful
        case "jwt":
            Debug.Log("Res was JWT");
            UserAccountManager.instance.LogIn((string)res["jwt"]);
            Debug.LogWarning("FINISHED");
            break;
        // Only 1 case for now
    }
};

UserAccountManager.cs

public static UserAccountManager instance;
void Awake() {
    if (instance != null)
    {
        Destroy(gameObject);
        return;
    }

    instance = this;
    DontDestroyOnLoad(this);
}

void Set_Jwt(string _jwt)
{
    Jwt = _jwt;
    Jwt_data = decode_jwt(_jwt);

    playerUsername = (string)Jwt_data["username"];
    Debug.Log("Jwt set");
    Debug.LogWarning(playerUsername);
}

private JObject decode_jwt(string _jwt)
{
    string[] splitted = _jwt.Split('.');
    var part = splitted[1];
    // Code only runs until here
    byte[] _dec = Convert.FromBase64String(part);
    string decodedjwt = Encoding.UTF8.GetString(_dec);

    return JObject.Parse(decodedjwt);
}

public void LogIn(string _jwt) {
    Debug.LogWarning("LogIn called");
    Set_Jwt(_jwt);

    isLoggedIn = true;
    Debug.Log("Trying to load " + loggedInSceneName);
    SceneManager.LoadScene(loggedInSceneName);
}

EDIT:

I have written almost the same code in a new C# ConsoleApplication, and it throws a System.FormatException: "Invalid Length for base64 Char array"

static void Main(string[] args)
    {
        string jwt = "eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzUxMiJ9.eyJpc3MiOiJncy5hd2Vzb21lc3R1ZmYuYXQiLCJpYXQiOjE1MTA1OTkyNzQsImV4cCI6MTUxMDYwMjg3MywidWlkIjoiMTY1ZWMxZjAtYzhhNC0xMWU3LTk2ZWQtYzNjNGQ4NTRmM2I4IiwiYXV0aCI6dHJ1ZSwidXNlcm5hbWUiOiJnYWJlbml6aGVyZSIsImlwIjoiMTk0LjIwOC4xMzguMTI4IiwianRpIjoiNjg4NWM0N2YtMjk3NS00N2MyLTgzYTktN2RmMjhmODE3NDljIn0.tRhx3mUbGBxoGFFr0t6dnPMrdlUT4UKJKLBY_9IiJdBePWp1S10Z91875z6OFK92ymACRR_wO3_1_h6fKXAPTQ";
        string[] splitted = jwt.Split('.');
        var part = splitted[1];

        byte[] arr = Convert.FromBase64String(part);
        string res = Encoding.UTF8.GetString(arr);
        Console.WriteLine(res);

        Console.Read();
    }

What should I do now?

Answer 1

I finally fixed it. It was a very tiny mistake. The whole token was correct b64, but when I split out the middle part it was dividable by 4. I added a = and then it decoded fine.