Наглядный пример, как сделать онлайн редактор используя SignalR и ASP.NET Core 2.1
https://blog.elmah.io/building-a-cloud-editor-with-signalr-and-asp-net-core-2-1/
https://blog.elmah.io/building-a-cloud-editor-with-signalr-and-asp-net-core-2-1/
elmah.io Blog - .NET Technical tutorials/guides and new features
Building a cloud editor with SignalR and ASP.NET Core 2.1
With the release of 2.1, we now have support for SignalR in ASP.NET Core. In this tutorial, we show you how to build a collaborative editor with SignalR