Update an Existing Account

SalesforceSession salesforceSession = new SalesforceSession(new LoginDetails("username@example.com", "salesforcePassword"));  
AccountService accountService = new AccountService(salesforceSession);
Id accountId = (Id)"00190000002G9cF";
Account account = new Account(accountId);
// Set the updated value 
account.NumberOfEmployees = 8000;
SaveResult result = accountService.UpdateEntity(account);
Assert.IsTrue(result.success);
Assert.AreEqual(accountId, (Id)result.id);