Install .NET Core 2.1 (#331)

Author: pascalberger

.appveyor.yml

@@ -1,8 +1,18 @@
 #---------------------------------#
 #  Build Image                    #
 #---------------------------------#
-# Cake recipe requires .NET Core 2.1 which is not available on newer images
-image: Visual Studio 2019
+image: Visual Studio 2022
+
+#---------------------------------#
+#  Install .NET                   #
+#---------------------------------#
+install:
+  - ps: $env:DOTNET_INSTALL_DIR = "$pwd\.dotnetsdk"
+  - ps: mkdir $env:DOTNET_INSTALL_DIR -Force | Out-Null
+  - ps: Invoke-WebRequest -Uri "https://dotnet.microsoft.com/download/dotnet/scripts/v1/dotnet-install.ps1" -OutFile "$($env:DOTNET_INSTALL_DIR)/dotnet-install.ps1"
+  - ps: '& "$($env:DOTNET_INSTALL_DIR)/dotnet-install.ps1" -Version 2.1.818 -InstallDir $env:DOTNET_INSTALL_DIR'
+  - ps: $env:Path = "$env:DOTNET_INSTALL_DIR;$env:Path"
+  - ps: dotnet --info
 
 #---------------------------------#
 #  Build Script                   #