Adding Bootstrap 4 to Asp.Net Core MVC solution

To add Bootstrap 4 or newer to an Asp.NET Core MVC Solution, you can do this in the following manner if you use Visual Studio 2019 and .Net Core 3.1. Or at least have access to the 'Manage Client-side Libraries' functionality. Bootstrap is not supported in Nuget and definately not for .Net Core apps, so you need to add it manually using this. The Manage client-side libaries in Visual Studio adds a libman.json file. This is the Library Manager json file, similar to NPM based solutions package.json. Now add the following into libman.json:

{
  "version": "1.0",
  "defaultProvider": "cdnjs",
  "libraries": [
    {
      "library": "twitter-bootstrap@4.2.1",
      "destination": "wwwroot/lib/bootstrap",
      "files": [
        "js/bootstrap.bundle.js",
        "css/bootstrap.min.css"
      ]
    },
    {
      "library": "jquery@3.3.1",
      "destination": "wwwroot/lib/jquery",
      "files": [
        "jquery.min.js"
      ]
    }
  ]
}

This adds Bootstrap 4.2.1 and Jquery 3.3.1 into wwwroot lib folders for each library. Now in your _Layout.cshtml file (or the file you use as your Layout file), just drag bootstrap.min.css file and bootstrap.bundle.js files into that razor file. After you restart the solution, you should have Bootstrap 4 available into your Asp.Net Core MVC app! And if you want to add client side libraries using a GUI, select your project and choose then via right click Add->Client side library. Here you can search for client side libraries.