Update clients in asp.net core 2.0 using SignalR

I am going through several examples on Asp.net Core WebAPI with SignalR where most of them are demonstrating simple chat application where this is what Hub returns:

return Clients.All.InvokeAsync("Send", message);

And this is how it gets called in Startup.cs


The above example is good if message is not be send and updated to all the clients. In my case I have several APIs to be called whenever a data is changed:

Like Bank Transaction is done, I have to update ledger and several other reports at client side. But I don't see any option to pass Json.

Not finding exactly how to do this so that WebAPI gets refreshed everytime a change is there in the database.

As far as I understood, here "chat" is the endpoint which will be called from the frontend.

In this case what will happen to the endpoint I have created so far. Have a look at the below code example:

This api is to be called every time an entry is done:

 public async Task<object> GetMarket(string marketshortcode)
          Markets market = new Markets(marketshortcode);
          return market.GetMarket();

and this the entry:

        public async Task<object> sellCurUser([FromBody] SellCur model)
            if (model != null)
                SellCurUser suser = new SellCurUser();
                suser.sellcur = model;
                my addition code...

             return ....   

There are several more endpoints which needs to be called at certain update/creation.

Now the point is how these apis will be changed or even not changed at all.

Do anyone have any example to understand it simply.