asp.net mvc - How does show the updates asynchronously?

on stack overflow site, can see following updates asynchronously.

1. reputation changes
2. new question added in question list
3. new comment added, etc.

as per understanding, can done in xmlhttprequest (xhr) request asynchronously, maybe of setinterval.

confusions: in firefox, no xhr request coming , can see above changes asynchronously.

which kind of implementation , how can done in asp.net mvc?

this impressive , beautiful stuff asynchronous calls made client server using ajax.

a simple approach use jquery ajax make asynchronous call inside setinterval search "updates" of question (this question id 17779628. can see on url =p). so, call server can pass id , timestamp (a date) of last call made server. server brings updates occurred timestamp datetime.now.

i not sure real implementation of stack overflow, did lot of stuff this.

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another tip:

there improvement. ;) modern browsers contains implementations of websocket. since sockets "peer-to-peer" , not "client-server", modern browsers don't need approach setinterval. instead, can implement websocket opening in javascript , server can send updates actively in moment happens (you can use design patterns include events).

take @ caniuse see browsers supports websocket.

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edit

anyway, opened code you. stack overflow's javascript code uses singleton design pattern javascript code. take @ stackexchange variable in browser console. heart of javascript code here. can see, there whole api built upon stackexchange variable. now, search stackexchange.realtime.init('sockets.ny.stackexchange.com:80');

then, take @ implementation of stackexchange.realtime.init @ console. seems support asynchronous updates websocket. nice , modern, supported new browser versions. if need maintain backward compatibility, can support both websocket (for new) , ajax implementation (for old browsers).