Nuget says packages are missing, Package Manager Restore says all packages are installed

Question

What have I done to my Solution!? D:

I'm not able to install anything from nuget anymore. At first I kept getting an error saying:

An error occurred while trying to restore packages. A root element is missing.

So pursuant to this answer on another question, I renamed all my packages folders to packages-old, started VS again and attempted a restore. The error persists and I still can't install any nuget packages.

Error List:

Severity Code Description Project File Line Suppression State

Error This project references NuGet package(s) that are missing on this computer. Use NuGet Package Restore to download them. For more information, see http://go.microsoft.com/fwlink/?LinkID=322105. The missing file is ..\packages\Microsoft.Net.Compilers.1.3.2\build\Microsoft.Net.Compilers.props.

Package Manager Restore:

All packages are already installed and there is nothing to restore.
Time Elapsed: 00:00:00.0644890
========== Finished ==========

Additionally, there's a bunch of warnings most of which say the referenced component couldn't be found:

WarningIDE0006Error encountered while loading the project. Some project features, such as full solution analysis for the failed project and projects that depend on it, have been disabled.

Warning The referenced component 'System' could not be found.

Warning The referenced component 'Microsoft.Web.Infrastructure' could not be found.

Warning The referenced component 'System.Web.Services' could not be found.

Warning The referenced component 'System.Configuration' could not be found.

Warning The referenced component 'System.Web.ApplicationServices' could not be found.

Warning The referenced component 'Antlr3.Runtime' could not be found.

Warning The referenced component 'System.Web.WebPages.Razor' could not be found.

Warning The referenced component 'Microsoft.AI.Web' could not be found.

Warning The referenced component 'System.Web' could not be found.

Warning The referenced component 'Microsoft.CodeDom.Providers.DotNetCompilerPlatform' could not be found.

Warning The referenced component 'Microsoft.AI.DependencyCollector' could not be found.

Warning The referenced component 'Microsoft.AI.PerfCounterCollector' could not be found.

Warning The referenced component 'Microsoft.ApplicationInsights' could not be found.

Warning The referenced component 'System.ComponentModel.DataAnnotations' could not be found.

Warning The referenced component 'System.Web.DynamicData' could not be found.

Warning The referenced component 'Newtonsoft.Json' could not be found.

Warning The referenced component 'System.Web.Routing' could not be found.

Warning The referenced component 'System.EnterpriseServices' could not be found.

Warning The referenced component 'System.Xml' could not be found.

Warning The referenced component 'System.Web.Abstractions' could not be found.

Warning The referenced component 'System.Web.Mvc' could not be found.

Warning The referenced component 'System.Web.Optimization' could not be found.

Warning The referenced component 'System.Net.Http' could not be found.

Warning The referenced component 'System.Net.Http.WebRequest' could not be found.

Warning The referenced component 'System.Web.WebPages.Deployment' could not be found.

Warning The referenced component 'System.Web.Helpers' could not be found.

Warning The referenced component 'System.Web.Razor' could not be found.

Warning The referenced component 'Microsoft.AI.ServerTelemetryChannel' could not be found.

Warning The referenced component 'Microsoft.AI.Agent.Intercept' could not be found.

Warning The referenced component 'System.Xml.Linq' could not be found.

Warning The referenced component 'WebGrease' could not be found.

Warning The referenced component 'System.Drawing' could not be found.

Warning The referenced component 'System.Core' could not be found.

Warning The referenced component 'Microsoft.CSharp' could not be found.

Warning The referenced component 'System.Web.Extensions' could not be found.

Warning The referenced component 'Microsoft.AI.WindowsServer' could not be found.

Warning The referenced component 'System.Data.DataSetExtensions' could not be found.

Warning The referenced component 'System.Web.Entity' could not be found.

Warning The referenced component 'System.Web.WebPages' could not be found.

Warning The referenced component 'System.Data' could not be found.

Answer 1

An error occurred while trying to restore packages. A root element is missing.

When you get this error, you should make sure any XML file (or any file that would be interpreted as an XML file by visual studio, especially, nuget.config, .csproj. web.config,web.config.transform, and so on) has a correct XML structure - that is, one root element, for example, the <configuration> in the nuget.config file:

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <packageSources>
    <add key="nuget.org" value="https://api.nuget.org/v3/index.json" protocolVersion="3" />
  </packageSources>
</configuration>

To detect the source of the error A root element is missing, you can create a new blank solution with a project. Then install any nuget package, if that error still exists, you should special inspect the file, nuget.config in the folder %appdata%\NuGet. If that error disappears, the error should more related to your project files, .csproj, web.config, web.config.transform and so on.

All packages are already installed and there is nothing to restore.

Typically this error appears when the project is not loaded, so make sure all your projects in the solution are loaded when you restore on the solution.

Answer 2

To deal with this error, enter the following command in the Nuget console window:

Update-Package -reinstall  -ProjectName Your-Project-Name

This will update all missing files.