Hi Mlbrahim,
1. there is no tutorial for that; there is a simple tutorial for a
hello world .NET adapter and there are the sources of our StockList demo implemented in .NET. in the Lightstreamer server distribution under DOCS-SDKs/sdk_adapter_dotnet/examples/Remote_StockListDemo_Adapters/
2 To which client technology are you referring to? In any case yes, all of our client APIs can be used to subscribe to new items and unsubscribe from current items at runtime
HTH