I have set the postback URL but received no postback on orders placed using trading APIs in ASP.NET

How to get historical data

I am using Websocket to fetch live data for stocks. I have a requirrement to fetch index options data. Please can somebody confirm what value I need to pass to exchangeType? I tried using various values as mentioned in the code:

I have same problem get

How do I get historical Stock Data

I have set the postback URL but received no postback on orders placed using trading APIs in ASP.NET