Retrieving field from related record failing in API call

Hello guys,

I have two entities - E1 and E2.(They have a 1:N relationship). I have a function which is part of a series of API calls to the CRM. In this function, some parameters are passed which includes the GUID of the E1 record, and service. This function creates a E2 record. I want to assign the value of one of the fields from E1 record to a corresponding field in the E2 record.  I am using the below logic and it is not working.

/var productdetails = crmService.Retrieve(E1SchemaName, GuidOfE1Record, new ColumnSet("name"));
//var productName = (string)productdetails["name"];

E2record["productname"] = productName;