ASP.NET is an open source web framework, created by Microsoft, for building modern web apps and services with .NET.
ASP.NET is cross platform and runs on Windows, Linux, macOS, and Docker

Download .NET Framework
Install the latest version of dotnet from below link as per your application compatibility.
https://dotnet.microsoft.com/en-us/download/dotnet/

Note:
Before installing the dotnet latest version kindly discuss with your development team for application compatibility with latest version.