What RIC to use when an instrument changed name ?
When retrieving data for an instrument, for whatever date range, you must always use the current instrument name, i.e. the latest one. That will ensure you get all the data (even from historical periods when the instrument had a different name).
How to find out if an instrument changed name ?
When performing data extractions, instrument name changes that occurred in the last 10 days are delivered in the RIC maintenance report. You can find more information on that topic in this article, as well as here and in chapter 7 of the DSS GUI user guide. The main purpose of this is to allow you to manage your instrument lists, to make any necessary changes to ensure data retrieval consistency.
The case of GOOG.O and GOOGL.O
I see that both GOOGL.O and GOOG.O are currently quoted. GOOGL.O is the class A share, whereas GOOG.O is the class C share. Not being a data specialist, I cannot explain the difference between the two, nor what this implies as to instrument history
I'm not sure I answered your query, as I don't quite understand what information you would like to get using the .NET API. Hopefully the above clarifies a few things. If that does not suffice, please clarify your use case.
Please also note this forum is for software developers using Refinitiv APIs, and technical discussions. The moderators on this forum do not have deep expertise in the content sets available through our products to answer all questions. For data content queries, the best and speediest way to receive an answer is to open a content-related enquiry via MyRefinitiv or to call the Refinitiv Help Desk directly.