The .NET Framework is a software framework developed by Microsoft that runs primarily on Microsoft Windows. Dot net framework has a large class library called Framework Class Library (FCL). Its Free, Cross-platform and Open source tool. Supported on Windows, Linux, and macOS. Microsoft began developing .NET Framework in the late 1990s, originally under the name of Next Generation Windows Services (NGWS).
Download .Net Framework 3.5 offline Installer from MEGA
See all supported versions of Microsoft .net framework. Microsoft dotnet-framework from official website.