For Windows 8.1 and earlier versions, or Windows Server 2012 R2 and earlier versions:
Make sure that your Windows installation is up-to-date and includes KB2999226, which can be installed through Windows Update. If you don't have this update installed, you'll see an error like the following when you launch a .NET Core application: The program can't start because api-ms-win-crt-runtime-l1-1-0.dll is missing from your computer. Try reinstalling the program to fix this problem.
For Windows 7 or Windows Server 2008 R2:
In addition to KB2999226, make sure you also have KB2533623 installed. If you don't have this update installed, you'll see an error similar to the following when you launch a .NET Core application: The library hostfxr.dll was found, but loading it from C:\<path_to_app>\hostfxr.dll failed.