How can you find unused NuGet packages in solution?

Question

ReSharper 2016.1 has a feature to remove unused NuGet.

It can be run on a solution and on each project in a solution and it does the following things:

1. Analyze your code and collecting references to assemblies.
2. Build NuGet usage graph based on usages of assemblies.
3. Packages without content files, unused itself and without used dependencies are assumed as unused and suggested to remove.

Unfortunately, this doesn't work for project.json projects (RSRP-454515) and ASP.NET core projects (RSRP-459076)

You can use the Visual Studio Extension ResolveUR - Resolve Unused References.

Resolve unused references including nuget references in Visual Studio 2012/2013/2015 projects via menu item at solution and project nodes Solution Explorer Tool Window

It's not an easy task, so I suggest to make a backup and/or commit before, just in order to rollback if something went wrong.

You can accomplish this using ReSharper 2019.1.1.

Right click on the project > Refactor > Remove Unused References.

If your project is small, you can also use: project > Optimize Used References . . .

A window will pop up. Select all references and remove them all. Then go back and re-add the ones that give you a compiler error.

Below is a little PowerShell script that finds redundant NuGet packages for .NET Core / .NET 5+ projects. For each project file it removes every reference once and checks if it compiles. This will take a lot of time. After this you get a summary of each reference that might be excluded. In the end it is up to you do decide what should be removed. Most likely you will not be able to remove everything it suggest (due dependencies), but it should give you a good starting point.

Save the script below as a ps1-file and replace the string C:\MySolutionDirectory in line 89 with the directory you want to scan on and then run the ps1-file. Do an backup first in case something goes wrong.

function Get-PackageReferences {
    param($FileName, $IncludeReferences, $IncludeChildReferences)

    $xml = [xml] (Get-Content $FileName)

    $references = @()

    if($IncludeReferences) {
        $packageReferences = $xml | Select-Xml -XPath "Project/ItemGroup/PackageReference"

        foreach($node in $packageReferences)
        {
            if($node.Node.Include)
            {
                if($node.Node.Version)
                {
                    $references += [PSCustomObject]@{
                        File = (Split-Path $FileName -Leaf);
                        Name = $node.Node.Include;
                        Version = $node.Node.Version;
                    }
                }
            }
        }
    }

    if($IncludeChildReferences)
    {
        $projectReferences = $xml | Select-Xml -XPath "Project/ItemGroup/ProjectReference"

        foreach($node in $projectReferences)
        {
            if($node.Node.Include)
            {
                $childPath = Join-Path -Path (Split-Path $FileName -Parent) -ChildPath $node.Node.Include

                $childPackageReferences = Get-PackageReferences $childPath $true $true

                $references += $childPackageReferences
            }
        }   
    }

    return $references
}

function Get-ProjectReferences {
    param($FileName, $IncludeReferences, $IncludeChildReferences)

    $xml = [xml] (Get-Content $FileName)

    $references = @()

    if($IncludeReferences) {
        $projectReferences = $xml | Select-Xml -XPath "Project/ItemGroup/ProjectReference"

        foreach($node in $projectReferences)
        {
            if($node.Node.Include)
            {
                $references += [PSCustomObject]@{
                    File = (Split-Path $FileName -Leaf);
                    Name = $node.Node.Include;
                }
            }
        }
    }

    if($IncludeChildReferences)
    {
        $projectReferences = $xml | Select-Xml -XPath "Project/ItemGroup/ProjectReference"

        foreach($node in $projectReferences)
        {
            if($node.Node.Include)
            {
                $childPath = Join-Path -Path (Split-Path $FileName -Parent) -ChildPath $node.Node.Include

                $childProjectReferences = Get-ProjectReferences $childPath $true $true

                $references += $childProjectReferences
            }
        }   
    }

    return $references
}

$files = Get-ChildItem -Path C:\MySolutionDirectory -Filter *.csproj -Recurse

Write-Output "Number of projects: $($files.Length)"

$stopWatch = [System.Diagnostics.Stopwatch]::startNew()

$obseletes = @()

foreach($file in $files) {

    Write-Output ""
    Write-Output "Testing project: $($file.Name)"

    $rawFileContent = [System.IO.File]::ReadAllBytes($file.FullName)

    $childPackageReferences = Get-PackageReferences $file.FullName $false $true
    $childProjectReferences = Get-ProjectReferences $file.FullName $false $true

    $xml = [xml] (Get-Content $file.FullName)

    $packageReferences = $xml | Select-Xml -XPath "Project/ItemGroup/PackageReference"
    $projectReferences = $xml | Select-Xml -XPath "Project/ItemGroup/ProjectReference"

    $nodes = @($packageReferences) + @($projectReferences)

    foreach($node in $nodes)
    {
        $previousNode = $node.Node.PreviousSibling
        $parentNode = $node.Node.ParentNode
        $parentNode.RemoveChild($node.Node) > $null

        if($node.Node.Include)
        {
            $xml.Save($file.FullName)

            if($node.Node.Version)
            {
                $existingChildInclude = $childPackageReferences | Where-Object { $_.Name -eq $node.Node.Include -and $_.Version -eq $node.Node.Version } | Select-Object -First 1

                if($existingChildInclude)
                {
                    Write-Output "$($file.Name) references package $($node.Node.Include) ($($node.Node.Version)) that is also referenced in child project $($existingChildInclude.File)."
                    continue
                }
                else 
                {
                    Write-Host -NoNewline "Building $($file.Name) without package $($node.Node.Include) ($($node.Node.Version))... "
                }
            }
            else
            {
                $existingChildInclude = $childProjectReferences | Where-Object { $_.Name -eq $node.Node.Include } | Select-Object -First 1

                if($existingChildInclude)
                {
                    Write-Output "$($file.Name) references project $($node.Node.Include) that is also referenced in child project $($existingChildInclude.File)."
                    continue
                }
                else 
                {
                    Write-Host -NoNewline "Building $($file.Name) without project $($node.Node.Include)... "
                }
            }
        }
        else 
        {
            continue
        }

        dotnet build $file.FullName > $null

        if($LastExitCode -eq 0)
        {
            Write-Output "Building succeeded."

            if($node.Node.Version)
            {
                $obseletes += [PSCustomObject]@{
                    File = $file;
                    Type = 'Package';
                    Name = $node.Node.Include;
                    Version = $node.Node.Version;
                }
            }
            else
            {
                $obseletes += [PSCustomObject]@{
                    File = $file;
                    Type = 'Project';
                    Name = $node.Node.Include;
                }
            }
        }
        else 
        {
            Write-Output "Building failed."
        }


        if($null -eq $previousNode)
        {
            $parentNode.PrependChild($node.Node) > $null
        } 
        else 
        {
            $parentNode.InsertAfter($node.Node, $previousNode.Node) > $null
        }

        # $xml.OuterXml

        $xml.Save($file.FullName)
    }

    [System.IO.File]::WriteAllBytes($file.FullName, $rawFileContent)

    dotnet build $file.FullName > $null

    if($LastExitCode -ne 0)
    {
        Write-Error "Failed to build $($file.FullName) after project file restore. Was project broken before?"
        return
    }
}

Write-Output ""
Write-Output "-------------------------------------------------------------------------"
Write-Output "Analyse completed in $($stopWatch.Elapsed.TotalSeconds) seconds"
Write-Output "$($obseletes.Length) reference(s) could potentially be removed."

$previousFile = $null
foreach($obselete in $obseletes)
{
    if($previousFile -ne $obselete.File)
    {
        Write-Output ""
        Write-Output "Project: $($obselete.File.Name)"
    }

    if($obselete.Type -eq 'Package')
    {
        Write-Output "Package reference: $($obselete.Name) ($($obselete.Version))"
    }
    else
    {
        Write-Output "Project refence: $($obselete.Name)"
    }

    $previousFile = $obselete.File
}

You find more information here: https://devblog.pekspro.com/posts/finding-redundant-project-references

Visual Studio 2019 (version 16.9) has the remove-unused-packages function built-in, we will need to enable it manually now.

Go to Tools > Options > Text Editor > C# > Advanced > (Under the Analysis section) Tick Show "Removed Unused References" command

Visual Studio version 16.10 has the remove unused reference feature available. Right-click on the project > Remove Unused References.