Updated build documentation

docs/guidelines/build.md

@@ -2,7 +2,7 @@
 
 ## Windows
 
-Avalonia requires at least Visual Studio 2017 to build on Windows.
+Avalonia requires at least Visual Studio 2017 and .NET Core SDK 2.0 to build on Windows.
 
 ### Install GTK Sharp
 
@@ -22,69 +22,28 @@ git submodule update --init
 Open the `Avalonia.sln` solution in Visual Studio 2015 or newer. The free Visual Studio Community
 edition works fine. Run the `Samples\ControlCatalog.Desktop` project to see the sample application.
 
-## Linux
+## Linux/OSX
 
-### Install the latest version of Mono
+It's *not* possible to build the *whole* project on Linux/OSX. You can only build the subset targeting .NET Standard and .NET Core (which is, however, sufficient to get UI working on Linux/OSX). If you want to something that involves changing platform-specific APIs you'll need a Windows machine.
 
-To build Avalonia under Linux, you need to have a recent version of Mono installed. Mono is a cross-
-platform, open source .Net platform. There is a very good chance that the version of Mono that came
-with your Linux distribution is too old, so you want to install a more up-to-date version. The most
-convenient way to to this is through your package manager. The Mono project has great [installation
-instructions for many popular Linux distros](http://www.mono-project.com/docs/getting-started/install/linux).
+MonoDevelop, Xamarin Studio and Visual Studio for Mac aren't capable of properly opening our solution. You can use Rider (at least 2017.2 EAP) or VSCode instead. They will fail to load most of platform specific projects, but you don't need them to run on .NET Core.
 
-This will make the most up-to-date Mono release available through your package manager, and offer
-you updates as they become available.
+### Install the latest version of .NET Core
 
-Once you have your package manager configured for the Mono repository, install the `mono-devel`
-package, for example on ubuntu:
-
-```
-sudo apt-get install mono-devel
-```
-
-Once installed, check the version of mono to ensure it's at least 4.4.2:
-
-```
-mono --version
-```
+Go to https://www.microsoft.com/net/core and follow instructions for your OS. You need SDK (not just "runtime") package.
 
 ### Clone the Avalonia repository
 
 ```
 git clone https://github.com/AvaloniaUI/Avalonia.git
-git submodule update --init
-```
-
-### Restore nuget packages
-
-```
-cd Avalonia
-mkdir -p .nuget
-wget -O .nuget/nuget.exe https://dist.nuget.org/win-x86-commandline/latest/nuget.exe
-mono .nuget/nuget.exe restore Avalonia.sln
+git submodule update --init --recursive
 ```
 
 ### Build and Run Avalonia
 
-To build Avalonia in the `Debug` configuration:
-
 ```
-xbuild /p:Platform=Mono /p:Configuration=Debug Avalonia.sln
+samples/ControlCatalog.NetCore
+dotnet restore
+dotnet run
 ```
 
-You should now be able to run the ControlCatalog.Desktop sample:
-
-```
-mono ./samples/ControlCatalog.Desktop/bin/Debug/ControlCatalog.Desktop.exe
-```
-
-### Building Avalonia in MonoDevelop
-
-Flatpak version will *NOT* work. Version from https://github.com/cra0zy/monodevelop-run-installer/ might work if you are very lucky. Make sure that you have the latest version of Mono (from alpha update channel) and .NET Core SDK. Make sure to follow `FrameworkPathOverride` workaround from https://github.com/dotnet/sdk/issues/335
-
-### Building and running Avalonia in Rider
-
-For Linux/OSX you'll probably need to apply workaround from https://github.com/dotnet/sdk/issues/335
-
-Just add `export FrameworkPathOverride=/usr/lib/mono/4.6.1-api` (or `export FrameworkPathOverride=/Library/Frameworks/Mono.framework/Versions/Current/lib/mono/4.6.1-api` for OSX)
-