Query and Update a Person Account

Because Person Accounts are tightly coupled with Contacts, the Name field is compound and cannot be updated. Instead you must update FirstName and LastName.

SalesforceSession salesforceSession = new SalesforceSession(new LoginDetails("username@example.com", "salesforcePassword")); 
AccountService accountService = new AccountService(salesforceSession);

// This queries an existing Account record by 'Name' and retrieves all fields.
Account acct = accountService.GetSingleByFieldEquals(Account.Fields.Name, "John Smith");

// Change the FirstName.
acct.InternalFields[Contact.Fields.FirstName.Name] = "Jack";

// If we tried to update now, Salesforce would return INVALID_FIELD_FOR_INSERT_UPDATE error because we can't update 'Name'.

// Remove Name from the fields to be updated.
acct.InternalFields.Remove(Account.Fields.Name.Name);

// Now we can update successfully.
SaveResult result = accountService.UpdateEntity(acct);
Assert(result.success);