DATA BTC prices

YAHOO
https://www.google.nl/search?q=yahoo+finance+bitcoin+price&oq=yahoo+finance+bitcoin+price&aqs=chrome..69i57j69i64.6797j0j7&sourceid=chrome&ie=UTF-8

https://www.codeproject.com/Articles/1243860/Create-Stock-Charts-with-ASP-NET-Core-MVC-and-REST

Historic data
https://bitcoin.stackexchange.com/questions/4799/need-authoritative-source-for-historic-bitcoin-conversion-prices-from-all-exchan/4808#4808

https://bitcoincharts.com/about/markets-api/

http://api.bitcoincharts.com/v1/csv/

Coinbase has a REST API that gives you access to historical prices from their website. The data seems to show the Coinbase spot price (in USD) about every ten minutes. Results are returned in CSV format. You must query the page number you want through the API. There are 1000 results (or price points) per page. That's about 7 days' worth of data per page.

Bitstamp has live bitcoin data* that are publicly available in JSON at this link. Do not try to access it more than 600 times in ten minutes or else they'll block your IP (plus, it's unnecessary anyway; read more here). The below is a C# approach to getting live data:

using (var WebClient = new System.Net.WebClient())
{
var json = WebClient.DownloadString("https://www.bitstamp.net/api/ticker/");
string value = Convert.ToString(json);
// Parse/use from here
}