Use PackageReference instead of deprecated project.json for NuGet packages

[martinsuchan]

With Visual Studio 2017 the project.json system for managing NuGet packages has been deprecated. Visual Studio uses by default new PackageReference system where information about NuGet packages is stored inside the csproj file.

I think the current samples in master branch should be updated to use this new system. Separate branch could be preserved for VS2015 users.

Note as a part of this migration, the Microsoft.NETCore.UniversalWindowsPlatform NuGet should be also updated to the lastest one, currently version 6.0.6.

[oldnewthing]

Looks like it's not enabled for UWP yet. Web page says it requires Visual Studio 2017 Update 1 Preview 2. I asked VS 2017 (original flavor) to create a UWP project and it still created a project.json file. Once VS 2017 Update 1 becomes the baseline for samples, you can file a pull request that upgrades the projects to the new style. (Or at least convert one project and I'll replicate it to the other projects.)

[martinsuchan]

Visual Studio 2017 15.4 is here with full support for PackageReferences in UWP projects. Now is the right time to switch all samples to this NuGet package format.

[oldnewthing]

Great. If you create a pull request that converts one sample, I can propagate the change to the other samples. This is not my area of expertise, so I need somebody to show me what to do,

[EmilAlipiev]

@martinsuchan how can you tell UWP or nuget to use csproj instead of project.json? where is this information stored? I created a ticket on SO, maybe you can give me help
https://stackoverflow.com/questions/48211046/xamarin-uwp-project-doesnt-install-dependencies-from-nuget

[martinsuchan]

Hi, I've created sample pull request how to change project.json NuGet format to PackageReference NuGet format: #822
It's possible the Visual Studio team already has some kind of tool for batch updating projects to the new NuGet format.
How to do it manually - remember which NuGet packages are used in target project, delete the project.json file, close and reopen the project, right click the project to Manage NuGet Packages, add previously used NuGet packages -> In Visual Studio 2017 they are by default added in the new PackageReference NuGet format.
cc @oldnewthing @EmilAlipiev

[oldnewthing]

Thanks. I used your PR as a template and applied it to the other samples. Fix will go out at next refresh.