Hi,All.
   I created a new object type(such as objectA)  that had one field(such as account__c) to refer to some account.When I called API to change one objectA to refer to another account,there was a error:"Cannot specify both an external ID reference Account__r and a salesforce id, Account__c".
   code like that(C#):
         //the old value of objectA.Account__C is accountA,now set it accountB
         objectA.Account__c = accountB.Id;
  
   What is my problem?How to solve it?
   Thanks.