I know that for older versions of .NET, you can determine if a given version is installed by following
https://support.microsoft.com/en-us/kb/318785
I work primarily with Windows development machines and servers.
I just wanted to point out (at least for NET.Core 2.0 and above) the only thing needed is to execute dotnet --info in a command prompt to get information about the latest version installed. If .NET Core is installed you will get some response.
On my development machine (Windows 10) the result is as follows. SDK is 2.1.2 and runtime is 2.0.3.
.NET Command Line Tools (2.1.2)
Product Information:
Version: 2.1.2
Commit SHA-1 hash: 5695315371
Runtime Environment:
OS Name: Windows
OS Version: 10.0.15063
OS Platform: Windows
RID: win10-x64
Base Path: C:\Program Files\dotnet\sdk\2.1.2\
Microsoft .NET Core Shared Framework Host
Version : 2.0.3
Build : a9190d4a75f4a982ae4b4fa8d1a24526566c69df
On one of my servers running Windows Server 2016 with Windows Server Hosting pack (no SDK) result is as follows. No SDK, runtime is 2.0.3.
Microsoft .NET Core Shared Framework Host
Version : 2.0.3
Build : a9190d4a75f4a982ae4b4fa8d1a24526566c69df
Cheers !