The clearing number has the following structure:

• A leading char as check digit
• A four digit sequential number
• A two digit number circle / canton number

The leading char of the clearing number is created and validated as follows:

• Each number is multiplied with its position (calculate from the right end).
• All products are summarized into one sum.
• Modulo 26 of the sum denotes the char in the alphabet (result 0 results in char 'Z'). 

Example L248519:
(9*1)+(1*2)+(5*3)+(8*4)+(4*5)+(2*6) = 90
90 mod 26 = 12
12th char in the alphabet = L

The ECH0097 enterprise identification number (Unternehmensidentifikationsnummer UID, Numéro d’identification des entreprises IDE, Numero d’identificazione delle imprese IDI) has the following structure:

• ISO-Alpha-3 Code (ISO 3166-1) of Switzerland (CHE)
• 8 digit pseudo random number
• check digit

The check digit is created and validated as follows:

• Each digit of the pseudo-random number is multiplied with a predefined multiplier: 54327654
• All products are summarized into one sum.
• 11 minus Modulo 11 of the sum defines the check digit.

Example CHE-114.617.288:
(1*5)+(1*4)+(4*3)+(6*2)+(1*7)+(7*6)+(2*5)+(8*4) = 124
124 mod 11 = 3
11 - 3 = 8

{
  "access_token": "MTQ0NjOkZmQ5OTM5NDE9ZTZjNGZmZjI3",
  "refresh_token": "GEbRxBNZmQOTM0NjOkZ5NDE9ZedjnXbL",
  "token_type": "bearer",
  "expires_in": 300,
  "scope": "openid profile email offline_access roles c1s_profile cpr"
}

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</div>

        /// <summary>
        /// Loads the IAM configuration.
        /// </summary>
        private async Task<DiscoveryResponse> GetDiscoveryDocumentAsync(CancellationToken ct)
        {
            using (var client = new HttpClient())
            {
                var discoveryResponse = await client.GetDiscoveryDocumentAsync(new DiscoveryDocumentRequest
                {
                    Address = "[AuthorityUrl]"
                }, ct).ConfigureAwait(false);

                if (discoveryResponse.IsError)
                    throw new Exception(discoveryResponse.Error);

                return discoveryResponse;
            }
        }

        /// <summary>
        /// Gets a new token response with a username and password.
        /// </summary>
        private async Task<TokenResponse> RequestTokenAsync(CancellationToken ct)
        {
            using (var client = new HttpClient())
            {
                var discoveryResponse = await GetDiscoveryDocumentAsync(ct).ConfigureAwait(false);

                var tokenResponse = await client.RequestPasswordTokenAsync(new PasswordTokenRequest
                {
                    ClientId = "[ClientId]",
                    ClientSecret = "[ClientSecret]",
                    UserName = "[UserName]",
                    Password = "[Password]",
                    Address = discoveryResponse.TokenEndpoint,
                    GrantType = OidcConstants.GrantTypes.Password,
                    Scope = string.Join(" ", _scopes),
                }, ct).ConfigureAwait(false);

                if (tokenResponse.IsError)
                    throw new Exception(tokenResponse.Error);

                return tokenResponse;
            }
        }

        /// <summary>
        /// Gets the access token by either requesting a new token or by using the refresh token of an already existing token.
        /// </summary>
        private async Task<string> GetAccessTokenAsync(CancellationToken ct)
        {
            if (_tokenResponse == null)
            {
                // Creates a new token response
                _tokenResponse = await RequestTokenAsync(ct).ConfigureAwait(false);
            }
            else
            {
                var jwtSecurityTokenHandler = new JwtSecurityTokenHandler();

                // Parses JWT access token
                var jwtSecurityToken = jwtSecurityTokenHandler.ReadToken(_tokenResponse.AccessToken) as JwtSecurityToken;

                // The access token might be valid now, but expired the very next millisecond.
                // Thus, add a reasonable reserve in minutes for the validity time comparison below.
                var comparisionCorrectionInMinutes = 1;

                // Compares the access token life time with the current time, modified by the comparison correction value.
                if (jwtSecurityToken.ValidTo < DateTime.UtcNow.AddMinutes(comparisionCorrectionInMinutes))
                {
                    // Updates the existing token response
                    _tokenResponse = await RefreshTokenAsync(_tokenResponse.RefreshToken, ct).ConfigureAwait(false);
                }
            }

            return _tokenResponse.AccessToken;
        }

        /// <summary>
        /// Gets an updated token response by using a refresh token.
        /// </summary>
        private async Task<TokenResponse> RefreshTokenAsync(string refreshToken, CancellationToken ct)
        {
            using (var client = new HttpClient())
            {
                var discoveryResponse = await GetDiscoveryDocumentAsync(ct).ConfigureAwait(false);

                var tokenResponse = await client.RequestTokenAsync(new TokenRequest
                {
                    ClientId = "[ClientId]",
                    ClientSecret = "[ClientSecret]",
                    Address = discoveryResponse.TokenEndpoint,
                    ClientCredentialStyle = ClientCredentialStyle.AuthorizationHeader,
                    GrantType = OidcConstants.GrantTypes.RefreshToken,
                    Parameters =
                    {
                        { "refresh_token", refreshToken },
                        { "scope", string.Join(" ", _scopes) }
                    }
                });

                if (tokenResponse.IsError)
                    throw new Exception(tokenResponse.Error);

                return tokenResponse;
            }
        }

        /// <summary>
        /// A simple CPR API number search request.
        /// </summary>
        private async Task<BulkResponse> CprApiSampleRequestAsync(string accessToken, CancellationToken ct)
        {
            BulkResponse bulkResponse = new BulkResponse();

            using (var client = new HttpClient())
            {
                client.SetBearerToken(accessToken);

                var response = await client.GetAsync($"https://[CprBaseUrl]/ApiGateway/api/v1/numbers?searchOptions=Okp&offset=0&limit=10", ct).ConfigureAwait(false);

                if (!response.IsSuccessStatusCode)
                    throw new Exception("There was a problem with the request");

                string content = await response.Content.ReadAsStringAsync();

                if (content != null && content.Length > 0)
                {
                    bulkResponse = JsonConvert.DeserializeObject<BulkResponse>(content);
                }
            }

            return bulkResponse;
        }

        var accessToken = await GetAccessTokenAsync(ct).ConfigureAwait(false);

        var cprApiResponse = await CprApiSampleRequestAsync(accessToken, ct).ConfigureAwait(false);