static class SalesforceSettings
      {
          public const string OAuthTokenEndpoint = @"https://ap17.salesforce.com/services/oauth2/token";
          public const string Url = @"https://ap17.salesforce.com/services/data/v42.0";
          public const string ClientId = @"xxx";
          public const string ClientSecret = @"xxx";
          public const string Username = @"xxx";
          public const string Password = @"xxx";
          public const string SecurityToken = @"xxx";
      }
​
      static DataTable GetContactsFromSalesforce()
      {
          string sql = @"select c.FirstName, c.LastName, c.Salutation, c.Title, c.Email, c.Phone, c.MobilePhone, c.Fax,
                          c.MailingStreet, c.MailingCity, c.MailingState, c.MailingPostalCode, c.MailingCountry, c.MailingLatitude, c.MailingLongitude,
                          c.Description, a.Name as AccountName, a.AccountNumber From Contact c left join Account a on c.AccountId = a.Id";
​
          string salesforceConnection = string.Format("Username={0};Password={1};Security Token={2};OAuth Client Id={3}; OAuth Client Secret={4}; OAuth Token Endpoint={5}; Url={6}",
              SalesforceSettings.Username, SalesforceSettings.Password, SalesforceSettings.SecurityToken, SalesforceSettings.ClientId, SalesforceSettings.ClientSecret,
              SalesforceSettings.OAuthTokenEndpoint, SalesforceSettings.Url);
​
          using (var con = new C1SalesforceConnection(salesforceConnection))
          {
              con.Open();
              var command = con.CreateCommand();
              command.CommandText = sql;
​
              var contactsReader = command.ExecuteReader();
              var dataTable = new DataTable();
              dataTable.Load(contactsReader);
              return dataTable;
          }
      }

      static class QBOSettings
      {
          public static string OAuthAccessToken = @"xxx";
          public static string OAuthRefreshToken = @"xxx";
          public const string OAuthClientId = @"xxx";
          public const string OAuthClientSecret = @"xxx";
          public static string CompanyId = "xxx";
          public const string MinorVersion = "xxx";
​
          public static string ConnectionString => $"Company Id={CompanyId};Use SandBox=true;OAuth Client Secret={OAuthClientSecret};OAuth Client Id={OAuthClientId};" +
                          $"OAuth Access Token={OAuthAccessToken};OAuth Refresh Token={OAuthRefreshToken}; OAuth Token Endpoint=;Minor Version={MinorVersion}";
      }
​
          using (var conn = new C1QuickBooksOnlineConnection(QBOSettings.ConnectionString))
          {
              conn.OAuthTokenRefreshed += OnOAuthTokenRefreshed;
              conn.Open();
              ……
          }

  C1QuickBooksOnlineDataAdapter dataAdapter = new C1QuickBooksOnlineDataAdapter();
              var insertCmd = "Insert Into Customers(Title, GivenName, FamilyName, CompanyName, PrimaryPhone_FreeFormNumber," +
                  "Mobile_FreeFormNumber, Fax_FreeFormNumber, BillAddr_City, BillAddr_CountrySubDivisionCode, BillAddr_PostalCode, BillAddr_Country, BillAddr_Lat," +
                  "BillAddr_Long, Notes) VALUES (@p1, @p2, @p3, @p4, @p6, @p7, @p8, @p9, @p10, @p11, @p12, @p13, @p14, @p15)";
​
              dataAdapter.InsertCommand = new C1QuickBooksOnlineCommand(conn, insertCmd);
              dataAdapter.InsertCommand.Parameters.Add("@p1", DbType.String, "Salutation");
              dataAdapter.InsertCommand.Parameters.Add("@p2", DbType.String, "FirstName");
              dataAdapter.InsertCommand.Parameters.Add("@p3", DbType.String, "LastName");
              dataAdapter.InsertCommand.Parameters.Add("@p4", DbType.String, "AccountName");
              dataAdapter.InsertCommand.Parameters.Add("@p6", DbType.String, "Phone");
              dataAdapter.InsertCommand.Parameters.Add("@p7", DbType.String, "MobilePhone");
              dataAdapter.InsertCommand.Parameters.Add("@p8", DbType.String, "Fax");
              dataAdapter.InsertCommand.Parameters.Add("@p9", DbType.String, "MailingCity");
              dataAdapter.InsertCommand.Parameters.Add("@p10", DbType.String, "MailingState");
              dataAdapter.InsertCommand.Parameters.Add("@p11", DbType.String, "MailingPostalCode");
              dataAdapter.InsertCommand.Parameters.Add("@p12", DbType.String, "MailingCountry");
              dataAdapter.InsertCommand.Parameters.Add("@p13", DbType.String, "MailingLatitude");
              dataAdapter.InsertCommand.Parameters.Add("@p14", DbType.String, "MailingLongitude");
              dataAdapter.InsertCommand.Parameters.Add("@p15", DbType.String, "Description");
              dataAdapter.InsertCommand.UpdatedRowSource = UpdateRowSource.None;
​
              //Need to change row state to added for bulk insert to work
              dataTable.TableName = "Customers";
              foreach (DataRow curRow in dataTable.Rows)
              {
                  curRow.SetAdded();
              }
​
              dataAdapter.UpdateBatchSize = 100;
              int rowAffected = dataAdapter.Update(dataTable);