Avalonia requires at least Visual Studio 2017 and .NET Core SDK 2.0 to build on Windows.
For the moment under windows, you must have gtk-sharp installed. Note that after installing the package your machine may require a restart before GTK# is added to your path. We hope to remove or make this dependency optional at some point in the future.
git clone https://github.com/AvaloniaUI/Avalonia.git
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.
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.
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.
Go to https://www.microsoft.com/net/core and follow instructions for your OS. You need SDK (not just "runtime") package.
git clone https://github.com/AvaloniaUI/Avalonia.git
git submodule update --init --recursive
samples/ControlCatalog.NetCore
dotnet restore
dotnet run