Q:

.NET Core 3.0 does not appear in Visual Studio 2017? 

I'm trying to start using Blazor, and therefore I must start using .Net Core 3, but it does not appear to use it !!!! . 
I installed .Net Core 3 as  you can see: 
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional>dotnet --info
.NET Core SDK (reflecting any global.json):
 Version:   3.1.100
 Commit:    cd82f021f4

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.17763
 OS Platform: Windows
 RID:         win10-x64
 Base Path:   C:\Program Files\dotnet\sdk\3.1.100\

Host (useful for support):
  Version: 3.1.0
  Commit:  65f04fb6db

.NET Core SDKs installed:
  1.1.13 [C:\Program Files\dotnet\sdk]
  2.1.202 [C:\Program Files\dotnet\sdk]
  2.1.505 [C:\Program Files\dotnet\sdk]
  2.1.507 [C:\Program Files\dotnet\sdk]
  2.1.508 [C:\Program Files\dotnet\sdk]
  2.1.509 [C:\Program Files\dotnet\sdk]
  2.1.700 [C:\Program Files\dotnet\sdk]
  3.1.100 [C:\Program Files\dotnet\sdk]

.NET Core runtimes installed:
  Microsoft. AspNetCore. All 2.1.9 [C:\Program Files\dotnet\shared\Microsoft. AspNetCore. All]
  Microsoft. AspNetCore. All 2.1.11 [C:\Program Files\dotnet\shared\Microsoft. AspNetCore. All]
  Microsoft. AspNetCore. All 2.1.12 [C:\Program Files\dotnet\shared\Microsoft. AspNetCore. All]
  Microsoft. AspNetCore. All 2.1.13 [C:\Program Files\dotnet\shared\Microsoft. AspNetCore. All]
  Microsoft. AspNetCore. App 2.1.9 [C:\Program Files\dotnet\shared\Microsoft. AspNetCore. App]
  Microsoft. AspNetCore. App 2.1.11 [C:\Program Files\dotnet\shared\Microsoft. AspNetCore. App]
  Microsoft. AspNetCore. App 2.1.12 [C:\Program Files\dotnet\shared\Microsoft. AspNetCore. App]
  Microsoft. AspNetCore. App 2.1.13 [C:\Program Files\dotnet\shared\Microsoft. AspNetCore. App]
  Microsoft. AspNetCore. App 3.1.0 [C:\Program Files\dotnet\shared\Microsoft. AspNetCore. App]
  Microsoft. NETCore. App 1.0.15 [C:\Program Files\dotnet\shared\Microsoft. NETCore. App]
  Microsoft. NETCore. App 1.1.12 [C:\Program Files\dotnet\shared\Microsoft. NETCore. App]
  Microsoft. NETCore. App 2.0.9 [C:\Program Files\dotnet\shared\Microsoft. NETCore. App]
  Microsoft. NETCore. App 2.1.9 [C:\Program Files\dotnet\shared\Microsoft. NETCore. App]
  Microsoft. NETCore. App 2.1.11 [C:\Program Files\dotnet\shared\Microsoft. NETCore. App]
  Microsoft. NETCore. App 2.1.12 [C:\Program Files\dotnet\shared\Microsoft. NETCore. App]
  Microsoft. NETCore. App 2.1.13 [C:\Program Files\dotnet\shared\Microsoft. NETCore. App]
  Microsoft. NETCore. App 3.1.0 [C:\Program Files\dotnet\shared\Microsoft. NETCore. App]
  Microsoft. WindowsDesktop. App 3.1.0 [C:\Program Files\dotnet\shared\Microsoft. WindowsDesktop. App]

To install additional .NET Core runtimes or SDKs:
  https://aka.ms/dotnet-download

and I enabled this:

but as you can see I cannot choose .NET Core 3 !!! 

this is the version of Visual Studio : 

if anybody has an idea how to enable it I will be grateful !!! 

A:

.NET 3.0 Core SDK requires VS 2019 per this webpage

