There are lots of formats for video files, and each format typically requires a different player and a different way to configure the player. In ASP.NET Razor pages, you can play a video in a web page using the Video helper. To play the video on the page you can try out the below methods
https://learn.microsoft.com/en-us/aspnet/web-pages/overview/ui-layouts-and-themes/10-working-with-video
To download files you can use the WebClient.DownloadFile Method
https://learn.microsoft.com/en-us/dotnet/api/system.net.webclient.downloadfile?view=net-5.0
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