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How should I share the same NuGet package among multiple C# solutions?

I am working with Newtonsoft.Json (a.k.a. Json.net) now and multiple C# solutions need to reference it. Seems the most convenient and widely-used way is to install Newtonsoft.Json with NuGet package manager. But I find that the package is installed in the solution root directory (anyway, the installation is based on a given solution) and its size cannot just be neglected (a bit over 10M), so I wonder if there is an elegant way to share this package among different C# solutions.
I searched Google and found few satisfying results (maybe it's because I didn't express my requirement properly); the only sound answer is to create a .nuget folder both in the directory and in the solution and fill it with a NuGet.config file, as follows:
Create a .nuget folder in the root of the solution (by entering ".nuget.", actually)
Inside that folder, create a file NuGet.config.
In Visual Studio 2015, right click on the solution and add a new solution directory called “.nuget”
Right click on that folder and select to add an existing file and select the NuGet.config file created in (2).
Add content like this inside the NuGet.config file:
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<solution>
<add key="disableSourceControlIntegration" value="true" />
</solution>
<config>
<add key="repositoryPath" value="E:\JsonExamples\C#Examples\UseJsonInCSharp\packages" />
</config>
</configuration>
Restart Visual Studio 2015.
But that didn't work because the using directive
using Newtonsoft.Json;
is still not recognized! Maybe there are something else that must be done, which isn't known to me but is common sense to veterans? Or perhaps this is because the version of the Newtonsoft.Json is too new for this to work? Can somebody help me? thanks a lot!
One more word: I'm currently using VS 2017, but I only found answers related to VS 2015, so I wonder the previous approach, if somehow works on VS 2015, will ever work for VS 2017.

Lets first clarify some things about NuGet and references in projects:
The job of references in project is to tell what external code this projects must look into - you can NOT go around this, you have to make a reference to Newtonsoft.Json in every project you want to use it.
The job of NuGet is to download/restore the nuget in some folder - the default "dumb" setting for old pre NuGet 4 versions is to make a seperate packages folder in every solution. Lets Focus on how to make this smarter.
Option 1 (Recommended) - Migrate everything to PackageReference
It is available since NuGet 4 in VS 2017+ (i recommend at least VS 2017 15.7+ which got wizard for automatic migration from older nuget versions). This is the most clean way of referencing NuGets since PackageReference in project does not hardcode NuGet download location. Instead it leaves this decision to local NuGet settings. By Default it is set to "%USERPROFILE%\.nuget\packages". No nuget package is duplicated, it acts as global cache for this computer. To force all new project to use PackageReference by default you must modify NuGet.config, here is how: Defaulting Package Management to PackageReference
Option 2 - specify common NuGet location for all project in the same repository
NuGet config settings are loaded per Solution. Having a common config file for NuGet is recommended even if you use PackageReference since download location is just one of many settings you might want to centrally manage for all Solutions (the other popular one is a setting which external NuGet repositories you want to use). NuGet download location setting is ignored by new PackageReference so it is safe to use it in mix scenario. VERY IMPORTANT, projects using this old NuGet use hardcoded reference to NuGet folder, so everytime you change this NuGet location setting you have to manually fix all NuGet references in your every project (by editing .csproj file manually or be deleting and re-adding NuGets), so chose wisely and do not change.
Details on how to correctly set global NuGet.config:
So first let me explain how shared NuGet.config settings work. NuGet scans all NuGet.config files from solution location up the hierarchy to root drive (it also check all .nuget folders). If multiple config files are detected it takes the one closest to solution. So for example you have "C:\Code\Repository1\Project1\Solution1.sln". If you want to have common NuGet settings for every solution in Repository1 put config file to a location like this "C:\Code\Repository1\NuGet.config". Also make sure this is the only config file inside whole Repository1 folder. Next step is to decide where to download all packages, for example "C:\Code\Repository1\NuGetPackages". To make everything work dynamically on all computers put relative path inside NuGet.config like this:
add key="repositoryPath" value="NuGetPackages"

NuGet package management failed for referenced project

We have a solution that contains a project that uses TestFramework from NuGet.
We've another solution that references that project.
The project/solution file system structure looks like this:
- Tests
- Tests
- Properties
- AssemblyInfo.cs
- packages.config
- Tests.csproj
- Tests.sln
- RefToTests
- RefToTests.sln
RefToTests.sln contains a reference to Tests.csproj.
If I open the Tests.sln and try to build it I get an error that tells me that the referenced NuGet dependencies could not be found. No problem - open the NuGet management for solution, click restore and build it again. Works fine.
The same clean folder but now open RefToTests.sln. Same error. Same workflow. That restores the packages to RefToTest\packages. The project is looking for them at ..\packages what means Tests\packages. That will not build.
We tried to fix that by manually change the folder to the packages in the project file from ..\packages to $(SolutionDir)packages. That worked great. The missing packages are downloaded automatically (wow that doesn't work without that change).
But now let's update the package. The package manager is not able to find that references in the project file, leaves the old entries untouched and added completely new references. The project won't build in any solution. That seams to be a bug in NuGet project management. In my opinion the package resolution should crash if it finds $(SolutionDir) or the package management should be able to handle that.
But what is the solution? Changing the directory to $(SolutionDir) and check every project file after every update? Leave the specified folder as it is and never do a cleanup on the repository?

C# visual studio how to relocate nuget package folder?

I hired a contractor to do some coding for me. He setup nuget.config in the solution folder with the following repository path:
<configuration>
<solution>
<add key="disableSourceControlIntegration"
value="true" />
</solution>
<config>
<add key="repositoryPath"
value="../lib" />
</config>
</configuration>
And I'm not too happy about his decision: this will place the nuget package folder outside the solution folder. I can easily change the repository path, simply by setting:
value="../<mySolutionFolder>/lib" />
However when I do this a curious thing happens: every single reference that I use in my solution is now broken. And nothing that I change in the .csproj files or other *.config files will allow my projects to find their references.
The only workaround is to re-create each project in my solution by starting from scratch, and add->existing items, etc. and reference->manage nuget packages, and install every reference again.
I have many projects in my solution and performing this for every one is understandably time consuming.
I would like to know if there is an easy way?
It seems like there should be a way for Nuget and VS to play nicely so that I can easily move the repository folder to a different path location.

One way to fix the reference paths is to use the Package Manager Console.
From the Package Manager Console you can run the following command to reinstall the NuGet packages which will fix the hint paths for the references.
Update-Package -reinstall
This will reinstall all NuGet packages in the solution. I am assuming you have the code under source control so you can see what changes are made to the projects if you need to revert them after this reinstall.
There is more documentation on reinstalling NuGet packages on the NuGet documentation site.
Another way to fix this is to do a find and replace in the .csproj files to fix the hint path.

I encountered this problem when I moved the actual folders around in my solution. I usually do a find/replace with VS Code looking for >..\packages\ and replace it with >..\..\packages\. This time I did the following:
Perform Update-Package -Reinstall
this worked for everything with hint paths
does not work when your project uses NuGet packages to build your project because there are custom MSBuild statements that need to be manually fixed, see next step.
Edit the .csproj files manually that do not build, in my example:
<Import Project="..\..\packages\Microsoft.CodeDom.Providers.DotNetCompilerPlatform.1.0.8\build\net45\Microsoft.CodeDom.Providers.DotNetCompilerPlatform.props" Condition="Exists('..\..\packages\Microsoft.CodeDom.Providers.DotNetCompilerPlatform.1.0.8\build\net45\Microsoft.CodeDom.Providers.DotNetCompilerPlatform.props')" />
<Import Project="..\..\packages\Microsoft.Net.Compilers.2.4.0\build\Microsoft.Net.Compilers.props" Condition="Exists('..\..\packages\Microsoft.Net.Compilers.2.4.0\build\Microsoft.Net.Compilers.props')" />
Notice that there are 2 condition statements in the <Import> that use relative pathing to ..\..\packages.
Hopefully these steps will help someone else.

Package.config is used for put file somewhere else from the folder, it help best to not upload package unusually when you add something in your project through Nuget.
Try to copy the package to that folder (new path you set) or simply close the project, open it again and click on Restore after going to Manage project reference.

After trying all solutions posted here I could not escape one primary issue: references to non nuget items, such as System and System.Core remained invalid (yellow triangle listed next to them). Removing them and adding them did not make them valid again. Further (as we all know) Visual Studio is terrible and giving reasons for why a reference is considered invalid.
So while Matt's solution does indeed relocate the nuget package folder, the solution in not left in a working state. Further, updating hint paths did not help because those are specific to the nuget packages. I cannot explain why basic references suchas System also become invalid. Perhaps someone reading this a year from now can leave a message with an explanation.
What I ended up doing is rebuilding my entire project without a nuget.config file (I deleted it). This causes nuget to use all defaults. Downloaded packages get stored in \\<solution_folder>\packages\. After the solution was working again, I added back the nuget.config file but with the following removed:
<config>
<add key="repositoryPath"
value="../lib" />
</config>
...and removing that section causes nuget to rely on default behavior which turns out to be exactly what I wanted (installing packages to \packages, etc).
If anyone else is about to undertake this laborious effort, I found this SO solution helpful for moving folders and files from the old solution to the new one.

I managed to do this to my own solution without realising how (and ended up with a packages folder at the *.sln level and another one at The level below that) - but I'm pretty sure now that this all has to do with migrating from using a packages config file, to the new method of using package references. This can occur if you use a newer version of visual studio (which is possibly what your contractor did) or via a button/commend in NuGet, or via a right-click context menu.
One of the things that happens is the creation of a 'global' packages folder (the one at .sln level) which is meant to save your space since it means you can have multiple solutions using the same package without having huge duplicate package folders repeated in every solution.
I found this out when I was merging The text is two csproj files and needed to Google: import project difference to package reference
See https://learn.microsoft.com/en-us/nuget/reference/migrate-packages-config-to-package-reference

How do I combine an existing NuGet package for a CL with a Roslyn analyzer?

Information already exists on how to create a roslyn analyzer as a NuGet package and add a new Class Library to it.
My situation is the other way around: I have a Class Library with a .nuspec attached to it that's integrated with TFS and has a whole publishing infrastructure setup around it. Changing all this to work with the analyzer's .nuspec instead would be quite a hassle.
Can I add the analyzer to the existing NuGet package?

Yes you can!
Open your existing solution
Add a new project from the "Analyzer With Code Fix (NuGet + VSIX)" template
In your existing nuget project, add a normal reference to the analyzer's class library
Copy the tools\ folder to the root of the existing nuget project (including the .ps1 files)
Add these two lines to the existing .nuspec file:
<file src="$outdir$MyOrganisation.MyService.Analyzers.dll" target="analyzers\dotnet\cs" exclude="**\Microsoft.CodeAnalysis.*; **\System.Collections.Immutable.*;**\System.Reflection.Metadata.*; **\System.Composition.*" />
<file src="tools\*.ps1" target="tools\" />
You newly generated .nupkg will now have your analyzer included with it and add it to whichever project adds a reference to it.
For cleaning purposes, you might want to remove the Diagnostic.nuspec in your analyzer project as well as the AfterBuild event in the .csproj file.
Note: you can probably remove the exclude since you're now targetting a specific file whereas previously it used a wildcard to select all .dll files. I haven't tried it without it yet so I'll leave it in the answer for now.

How to debug into my nuget package deployed from TeamCity?

I have put a library that my team uses into a nuget package that is deployed from TeamCity into a network folder. I cannot debug into this code though! SymbolSource is one solution I have read about but I would much rather find some way to have access to the .pdb/source files directly from TeamCity. Does anyone know how to do this?
Edit. When I check 'Include Symbols and Source' in the Nuget Pack build step, TeamCity creates a .Symbol.nupkg in addition to the .nupkg file in the network folder. The .Symbol.nupkg contains the src and the .pdb file.
Edit. I unchecked 'Include Symbols and Source' on TeamCity and added the following to my nuspec file:
<files>
<file src="..\MyLibrary\bin\release\MyLibrary.dll" target="lib\net40" />
<file src="..\MyLibrary\bin\release\MyLibrary.pdb" target="lib\net40" />
<file src="..\MyLibrary\*.cs" target="src" />
<file src="..\MyLibrary\**\*.cs" target="src" />
</files>
This added the dll, the pdb, and the source files for my library in the nuget package and didn't generate a .Symbols file which I think is only needed for symbol servers.

Traditional method
Put the pdb in the NuGet package alongside the dll.
Add the source code to the Debug Source Files for the solution that references the package.
This means you'll be able to step through code and view exceptions, but you might have to find a file on disk and open it before you can set a breakpoint. Obviously you need to be careful that the source is at the right revision.
More detail on step
If you're currently packaging without a Nuspec, you'll need to create a Nuspec, then add the pdb to the list of files in the lib folder "NuGet spec" may be a useful command for generating the initial spec as defined in NuGet docs. Then ensure the Team City Nuget Pack step is referencing your new nuspec.
More detail on step 2
When you have a solution open, right click on Solution, select Properties...Common Properties...Debug Source Files, and add the root source directory for the relevant binary reference. Or see MSDN.
Note, you can't open the solution properties while debugging.
Still not hitting breakpoints?
Try disabling this from Tools->Options:
Modern way for public or private repos
To ensure the exact version of the source is available, embed it at build time.
From Visual Studio 2017 15.5+ you can add the EmbedAllSources property:
<Project Sdk="Microsoft.NET.Sdk">
<PropertyGroup>
<EmbedAllSources>true</EmbedAllSources>
Modern way for public repos
To keep your nuget and library size small, you can use the sourcelink package.
It generates a pdb that directs the debugger to the correct version of the file from your VCS provider (e.g. GitHub, BitBucket).

The latest version of dotPeek (free!) can act as a symbol server and generate pdb files on the fly. This has allowed me to debug into the dlls that are served via teamcity.
Download it here:
http://blog.jetbrains.com/dotnet/2014/04/09/introducing-dotpeek-1-2-early-access-program/
Instructions on how to set it up here.
https://web.archive.org/web/20160220163146/http://confluence.jetbrains.com/display/NETCOM/dotPeek+Symbol+Server+and+PDB+Generation

You could of course set-up & configure your own symbol server, but it's probably easiest to...
download and install Inedo's ProGet
enable symbol serving on the target feed
publish packages from TeamCity to the ProGet feed
use ProGet as your primary feed source (as it can aggregate multiple feeds including nuget.org)
All of this can be done with the free edition of ProGet.
disclaimer -- my day job is at Inedo

In your .nuspec (directly under <package>):
<files>
<file src="bin\$configuration$\$id$.pdb" target="lib\net451\" />
</files>
(change net451 to the platform you're compiling for)

If you have the source code for the package, then the foolproof (but possibly laborious) method is:
Add the source code for the package to your solution (right click Solution -> Add Existing Project)
Go through all of your projects in the solution and remove the NuGet reference to the library (i.e. open the References folder under each project and delete the reference to the package.) Then, add a reference to the NuGet package project in your solution. (i.e. Right click References, add Reference, choose Projects and tick the box for the project)
I had to do it this way when I the method I wanted to debug inside the NuGet package was called by the framework and not by my code, thus I couldn't step into it. (In my case, the method was an ASP.NET DelegatingHandler).
Once you're done you'll want to undo all your changes via source control so that the NuGet package is referenced correctly.

I've found a super simple way to do this, which I have blogged about here:
https://mattfrear.com/2017/11/29/speed-up-development-in-a-nuget-package-centric-solution/
This only works if you're using the new .NET Core style .csproj with <PackageReference> (on either .NET Core or .NET Framework).
This again assumes you have access to the source code of the NuGet package.
Build and compile the NuGet package on your local machine
Copy the .dll you've just compiled into your local NuGet packages feed folder (On my machine, this is C:\Users\matt\.nuget\packages\), overwriting the existing NuGet package .dll.
That's it! You should be able to step into the package while debugging. No messing around with .pdbs or source servers. This has greatly sped up my development cycle.

Since this question was originally posted, Jetbrains have written an entire blog post on how to accomplish this. The steps can be summarised as:
Install Debugging Tools for Windows on the agents.
Install & Enable the Symbol Server plugin.
Add Symbol Files Indexer build feature to your build configurations.
Ensure PDB files are output as an artefact.
Configure Visual Studio to use TeamCity as source server.
If you are using Nuget Package build steps, you can check 'Include Symbols and Source' to output a .symbol.nupkg which contains the PDBs. Depending on whether the Symbol Files Indexer is smart enough to look inside this file or not, you may need to change the file extension for things to work.
The full details are given here:
https://blog.jetbrains.com/teamcity/2015/02/setting-up-teamcity-as-symbol-and-source-server/

This is what I have found to work, but all the steps are probably not required...
Note: this doesn't allow you to debug both, only either the nuget
package or the solution in which it is installed.
Run Visual Studio as Administrator
Open and Start the host application (the one in which you installed the Nuget package) without debugging (Ctrl + F5)
In the Nuget package solution, ensure that Tools > Options > Debugging > General > "Require source files to exactly match the original version" is NOT checked.
Ensure that "Enable just my code" is NOT checked
Add a new folder in Tools > Options > Debugging > Symbols pointing to the source directory of the Nuget package. (You literally enter the folder path , see image below)
Click Debug > Attach to Process...
Find iisexpress (there may be multiple, it won't do any harm attaching to all)

If your code is in a public Git repository, or, at least in your network, is accessible without authentication, then GitLink would be an option:
https://github.com/GitTools/GitLink
GitLink makes symbol servers obsolete by changing the PDB to point to the Git server. But, as said before, this makes it necessary for the Git repository to be public - until now there's no "proper" way to authenticate when accessing a private repository.

Microsoft has now integrated the SourceLink NuGet package at https://github.com/dotnet/sourcelink/ which allows source code to be downloaded on demand while debugging if the publisher of the NuGet package sets it up.