尝试创建Xamarin.Forms macOS App：当前上下文中不存在名称“ LoadApplication”

Question

我正在尝试创建Xamarin.Forms Mac应用程序。我遵循了似乎有些过时的本指南，但我仍然可以遵循Visual Studio Mac 2017的步骤进行操作：

https://blog.xamarin.com/preview-bringing-macos-to-xamarin-forms/

在遵循指南时，我会陷入以下困境：

LoadApplication(new App());

它说：

The name 'LoadApplication' does not exist in the current context

我试图清理所有内容，仅构建PCL项目，删除并重新添加对MacOS项目的引用，如另一个问题所述，但运气不好。

我想念什么？

还是取消了macOS支持？

跟进1

在命令行上运行dotnet build时，我得到：

Microsoft (R) Build Engine version 15.7.179.6572 for .NET Core
Copyright (C) Microsoft Corporation. All rights reserved.

/Users/jens/tests/desktop/FormsTest/FormsTest.Mac/FormsTest.Mac.csproj(108,3): error MSB4019: The imported project "/usr/local/share/dotnet/sdk/2.1.302/Xamarin/Mac/Xamarin.Mac.CSharp.targets" was not found. Confirm that the path in the <Import> declaration is correct, and that the file exists on disk.

Build FAILED.

/Users/jens/tests/desktop/FormsTest/FormsTest.Mac/FormsTest.Mac.csproj(108,3): error MSB4019: The imported project "/usr/local/share/dotnet/sdk/2.1.302/Xamarin/Mac/Xamarin.Mac.CSharp.targets" was not found. Confirm that the path in the <Import> declaration is correct, and that the file exists on disk.
    0 Warning(s)
    1 Error(s)

Time Elapsed 00:00:00.10

那么，如何安装此“ Xamarin.Mac.CSharp.targets”？