Retrive Multiple using GUID of the record is some thing different from normal crietra like retrieve with first name last name.
In retrive multiple criteria we have to use new ConditionExpression like below
RetrieveAccountId.Criteria.AddCondition(new ConditionExpression("accountid", ConditionOperator.In, accountId));
Full code is followed for retrieving multiple records, displaying those retrieved records data using for each
Guid[] accountId = new Guid[1];
accountId[0] = new Guid("475b158c-541c-e511-80d3-3863bb347ba8");
var retrieveAccountId = new QueryExpression();
retrieveAccountId.EntityName = "account";
retrieveAccountId.ColumnSet = new ColumnSet(true);
retrieveAccountId.Criteria.AddCondition(new ConditionExpression("accountid", ConditionOperator.In, accountId));
EntityCollection AccountCollection = orgService.RetrieveMultiple(retrieveAccountId);
foreach (var account in AccountCollection.Entities)
{
Console.WriteLine("Account Name {0}", account["name"]);
}
Thats it..

