Chisel provides a way to remove unwanted dependencies from your dotnet projects.

Chisel was born because some database drivers can't resist taking dependencies on cloud libraries. The MongoDB driver depends on the ASW SDK for authentication with Identity and Access Management (IAM) and Microsoft's SQL Server driver depends on the Azure SDK for authentication with the Microsoft identity platform (formerly Azure AD).

Users have asked for separate NuGet packages for both MongoDB (issue #4635) and SqlClient (issue #1108) but as of MongoDB.Driver 2.24.0 and Microsoft.Data.SqlClient 5.2.0 the cloud dependencies are unavoidable, even if MongoDB or SQL Server is used on premises (where cloud authentication is obviously not needed).

Enter Chisel to remove those dependencies and save some precious megabytes.

Getting started

Add the Chisel NuGet package to your project using the NuGet Package Manager or run the following command:

dotnet add package Chisel

While Chisel's main purpose is removing unwanted dependencies from existing NuGet packages, it provides another great feature: a graph of your project's dependencies. After adding Chisel, a Mermaid (or Graphviz) graph is written in the intermediate output path (aka the obj directory).

For a project referencing Hangfire.PostgreSql and Npgsql.EntityFrameworkCore.PostgreSQL the graph would look like this.

graph LR

classDef default fill:aquamarine,stroke:#009061,color:#333333

Hangfire.Core --> Newtonsoft.Json
Hangfire.PostgreSql --> Dapper
Hangfire.PostgreSql --> Hangfire.Core
Hangfire.PostgreSql --> Npgsql
Microsoft.EntityFrameworkCore --> Microsoft.EntityFrameworkCore.Abstractions
Microsoft.EntityFrameworkCore --> Microsoft.Extensions.Caching.Memory
Microsoft.EntityFrameworkCore --> Microsoft.Extensions.Logging
Microsoft.EntityFrameworkCore.Relational --> Microsoft.EntityFrameworkCore
Microsoft.EntityFrameworkCore.Relational --> Microsoft.Extensions.Configuration.Abstractions
Microsoft.Extensions.Caching.Abstractions --> Microsoft.Extensions.Primitives
Microsoft.Extensions.Caching.Memory --> Microsoft.Extensions.Caching.Abstractions
Microsoft.Extensions.Caching.Memory --> Microsoft.Extensions.DependencyInjection.Abstractions
Microsoft.Extensions.Caching.Memory --> Microsoft.Extensions.Logging.Abstractions
Microsoft.Extensions.Caching.Memory --> Microsoft.Extensions.Options
Microsoft.Extensions.Caching.Memory --> Microsoft.Extensions.Primitives
Microsoft.Extensions.Configuration.Abstractions --> Microsoft.Extensions.Primitives
Microsoft.Extensions.DependencyInjection --> Microsoft.Extensions.DependencyInjection.Abstractions
Microsoft.Extensions.Logging --> Microsoft.Extensions.DependencyInjection
Microsoft.Extensions.Logging --> Microsoft.Extensions.Logging.Abstractions
Microsoft.Extensions.Logging --> Microsoft.Extensions.Options
Microsoft.Extensions.Logging.Abstractions --> Microsoft.Extensions.DependencyInjection.Abstractions
Microsoft.Extensions.Options --> Microsoft.Extensions.DependencyInjection.Abstractions
Microsoft.Extensions.Options --> Microsoft.Extensions.Primitives
Npgsql --> Microsoft.Extensions.Logging.Abstractions
Npgsql.EntityFrameworkCore.PostgreSQL --> Microsoft.EntityFrameworkCore
Npgsql.EntityFrameworkCore.PostgreSQL --> Microsoft.EntityFrameworkCore.Abstractions
Npgsql.EntityFrameworkCore.PostgreSQL --> Microsoft.EntityFrameworkCore.Relational
Npgsql.EntityFrameworkCore.PostgreSQL --> Npgsql

Mermaid graphs can be used directly in markdown files on GitHub and are rendered as graphs, just like the one just above. Or they can also be edited, previewed and shared with the Mermaid live editor.

Graphviz (DOT) files can be written instead by setting the ChiselGraphName property to a name that ends with .gv:

<PropertyGroup>
  <ChiselGraphName>$(MSBuildProjectName).Chisel.gv</ChiselGraphName>
</PropertyGroup>

Graphviz files can be visualized and shared online with Edotor or locally with the excellent Graphviz Interactive Preview extension for Visual Studio Code.

Warning

While this technique has been sucessfully tested with the MongDB driver and the SQL Server driver, removing dependencies from a package might lead to exceptions at runtime. Make sure to properly test your application.

Removing the AWS SDK from MongoDB.Driver

After adding the Chisel package to your project, tell it to remove the AWSSDK.SecurityToken dependency with the ChiselPackage property.

<PropertyGroup>
  <ChiselPackage>AWSSDK.SecurityToken</ChiselPackage>
</PropertyGroup>

Specifying the direct dependencies is enough. Looking at the produced graph confirms that Chisel figured out the transitive dependencies by itself (there's only AWSSDK.Core in this scenario).

graph LR

classDef default fill:aquamarine,stroke:#009061,color:#333333
classDef removed fill:lightcoral,stroke:#A42A2A

AWSSDK.SecurityToken/3.7.100.14 --> AWSSDK.Core/3.7.100.14
DnsClient/1.6.1 --> Microsoft.Win32.Registry/5.0.0
Microsoft.Extensions.Logging.Abstractions/8.0.1 --> Microsoft.Extensions.DependencyInjection.Abstractions/8.0.1
Microsoft.Win32.Registry/5.0.0 --> System.Security.AccessControl/5.0.0
Microsoft.Win32.Registry/5.0.0 --> System.Security.Principal.Windows/5.0.0
MongoDB.Bson/2.24.0 --> System.Runtime.CompilerServices.Unsafe/6.0.0
MongoDB.Driver/2.24.0 --> Microsoft.Extensions.Logging.Abstractions/8.0.1
MongoDB.Driver/2.24.0 --> MongoDB.Bson/2.24.0
MongoDB.Driver/2.24.0 --> MongoDB.Driver.Core/2.24.0
MongoDB.Driver/2.24.0 --> MongoDB.Libmongocrypt/1.8.2
MongoDB.Driver.Core/2.24.0 --> AWSSDK.SecurityToken/3.7.100.14
MongoDB.Driver.Core/2.24.0 --> DnsClient/1.6.1
MongoDB.Driver.Core/2.24.0 --> Microsoft.Extensions.Logging.Abstractions/8.0.1
MongoDB.Driver.Core/2.24.0 --> MongoDB.Bson/2.24.0
MongoDB.Driver.Core/2.24.0 --> MongoDB.Libmongocrypt/1.8.2
MongoDB.Driver.Core/2.24.0 --> SharpCompress/0.30.1
MongoDB.Driver.Core/2.24.0 --> Snappier/1.0.0
MongoDB.Driver.Core/2.24.0 --> ZstdSharp.Port/0.7.3
System.Security.AccessControl/5.0.0 --> System.Security.Principal.Windows/5.0.0

class AWSSDK.Core/3.7.100.14 removed
class AWSSDK.SecurityToken/3.7.100.14 removed
class DnsClient/1.6.1 default
class Microsoft.Extensions.DependencyInjection.Abstractions/8.0.1 default
class Microsoft.Extensions.Logging.Abstractions/8.0.1 default
class Microsoft.Win32.Registry/5.0.0 default
class MongoDB.Bson/2.24.0 default
class MongoDB.Driver/2.24.0 default
class MongoDB.Driver.Core/2.24.0 default
class MongoDB.Libmongocrypt/1.8.2 default
class SharpCompress/0.30.1 default
class Snappier/1.0.0 default
class System.Runtime.CompilerServices.Unsafe/6.0.0 default
class System.Security.AccessControl/5.0.0 default
class System.Security.Principal.Windows/5.0.0 default
class ZstdSharp.Port/0.7.3 default

Now, both AWSSDK.Core.dll and AWSSDK.SecurityToken.dll have disappeared from the build output.

As long as the MONGODB-AWS authentication mechanism is not used everything will work fine. See the MongoDbSample project in the samples directory.

Removing the Azure SDK from Microsoft.Data.SqlClient

Getting rid of the Azure/Microsoft Identity bits requires defining three packages to remove plus an additional trick. In the previous example, <ChiselPackage> was used as an MSBuild property. Here, it's used as an MSBuild item (i.e. with the Include attribute) to specify multiple packages.

<ItemGroup>
  <ChiselPackage Include="Azure.Identity" />
  <ChiselPackage Include="Microsoft.IdentityModel.JsonWebTokens" />
  <ChiselPackage Include="Microsoft.IdentityModel.Protocols.OpenIdConnect" />
</ItemGroup>

As with the MongoDB driver, specifying the three direct dependencies is enough. We can see in the produced graph that the Microsoft.Identity* libraries have many transitive dependencies which are also removed (in red).

graph LR

classDef default fill:aquamarine,stroke:#009061,color:#333333
classDef project fill:skyblue,stroke:#05587C
classDef removed fill:lightcoral,stroke:#A42A2A

Azure.Core --> Microsoft.Bcl.AsyncInterfaces
Azure.Core --> System.Diagnostics.DiagnosticSource
Azure.Core --> System.Memory.Data
Azure.Core --> System.Text.Encodings.Web
Azure.Core --> System.Text.Json
Azure.Identity --> Azure.Core
Azure.Identity --> Microsoft.Identity.Client
Azure.Identity --> Microsoft.Identity.Client.Extensions.Msal
Azure.Identity --> System.Security.Cryptography.ProtectedData
Azure.Identity --> System.Text.Json
Microsoft.Data.SqlClient --> Azure.Identity
Microsoft.Data.SqlClient --> Microsoft.Identity.Client
Microsoft.Data.SqlClient --> Microsoft.IdentityModel.JsonWebTokens
Microsoft.Data.SqlClient --> Microsoft.IdentityModel.Protocols.OpenIdConnect
Microsoft.Data.SqlClient --> Microsoft.SqlServer.Server
Microsoft.Data.SqlClient --> System.Configuration.ConfigurationManager
Microsoft.Data.SqlClient --> System.Runtime.Caching
Microsoft.Identity.Client.Extensions.Msal --> Microsoft.Identity.Client
Microsoft.Identity.Client.Extensions.Msal --> System.IO.FileSystem.AccessControl
Microsoft.Identity.Client.Extensions.Msal --> System.Security.Cryptography.ProtectedData
Microsoft.IdentityModel.JsonWebTokens --> Microsoft.IdentityModel.Tokens
Microsoft.IdentityModel.JsonWebTokens --> System.Text.Encodings.Web
Microsoft.IdentityModel.JsonWebTokens --> System.Text.Json
Microsoft.IdentityModel.Logging --> Microsoft.IdentityModel.Abstractions
Microsoft.IdentityModel.Protocols --> Microsoft.IdentityModel.Logging
Microsoft.IdentityModel.Protocols --> Microsoft.IdentityModel.Tokens
Microsoft.IdentityModel.Protocols.OpenIdConnect --> Microsoft.IdentityModel.Protocols
Microsoft.IdentityModel.Protocols.OpenIdConnect --> System.IdentityModel.Tokens.Jwt
Microsoft.IdentityModel.Tokens --> Microsoft.IdentityModel.Logging
Microsoft.IdentityModel.Tokens --> System.Security.Cryptography.Cng
System.Configuration.ConfigurationManager --> System.Diagnostics.EventLog
System.Configuration.ConfigurationManager --> System.Security.Cryptography.ProtectedData
System.Diagnostics.DiagnosticSource --> System.Runtime.CompilerServices.Unsafe
System.IdentityModel.Tokens.Jwt --> Microsoft.IdentityModel.JsonWebTokens
System.IdentityModel.Tokens.Jwt --> Microsoft.IdentityModel.Tokens
System.IO.FileSystem.AccessControl --> System.Security.AccessControl
System.IO.FileSystem.AccessControl --> System.Security.Principal.Windows
System.Memory.Data --> System.Text.Encodings.Web
System.Memory.Data --> System.Text.Json
System.Runtime.Caching --> System.Configuration.ConfigurationManager
System.Security.AccessControl --> System.Security.Principal.Windows

class Azure.Core removed
class Azure.Identity removed
class Microsoft.Bcl.AsyncInterfaces removed
class Microsoft.Data.SqlClient default
class Microsoft.Identity.Client project
class Microsoft.Identity.Client.Extensions.Msal removed
class Microsoft.IdentityModel.Abstractions removed
class Microsoft.IdentityModel.JsonWebTokens removed
class Microsoft.IdentityModel.Logging removed
class Microsoft.IdentityModel.Protocols removed
class Microsoft.IdentityModel.Protocols.OpenIdConnect removed
class Microsoft.IdentityModel.Tokens removed
class Microsoft.SqlServer.Server default
class System.Configuration.ConfigurationManager default
class System.Diagnostics.DiagnosticSource removed
class System.Diagnostics.EventLog default
class System.IdentityModel.Tokens.Jwt removed
class System.IO.FileSystem.AccessControl removed
class System.Memory.Data removed
class System.Runtime.Caching default
class System.Runtime.CompilerServices.Unsafe removed
class System.Security.AccessControl removed
class System.Security.Cryptography.Cng removed
class System.Security.Cryptography.ProtectedData default
class System.Security.Principal.Windows removed
class System.Text.Encodings.Web removed
class System.Text.Json removed

Notice how Microsoft.Identity.Client is in blue (meaning it's a project reference instead of a package reference). That's because the Microsoft.Identity.Client package can't be easily removed, else the following exception would be thrown at runtime when opening a connection.

System.TypeInitializationException: The type initializer for 'Microsoft.Data.SqlClient.SqlAuthenticationProviderManager' threw an exception.
 ---> System.IO.FileNotFoundException: Could not load file or assembly 'Microsoft.Identity.Client, Version=4.56.0.0, Culture=neutral, PublicKeyToken=0a613f4dd989e8ae'. The system cannot find the file specified.

But it's possible to workaround this problem! Since the Microsoft.Identity.Client dll is required, we can create one with the absolute minimum required for the SqlAuthenticationProviderManager class to be happy.

1. Create a project named Microsoft.Identity.Client with the following content (also available in the samples directory):

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TargetFramework>netstandard2.0</TargetFramework>
    <DebugType>none</DebugType>
    <Version>4.56.0</Version>
    <SignAssembly>true</SignAssembly>
    <AssemblyOriginatorKeyFile>$(BaseIntermediateOutputPath)MSAL.snk</AssemblyOriginatorKeyFile>
  </PropertyGroup>

  <Target Name="DownloadMsalKey" BeforeTargets="ResolveKeySource" Condition="!Exists($(AssemblyOriginatorKeyFile))">
    <DownloadFile SourceUrl="https://github.com/AzureAD/microsoft-authentication-library-for-dotnet/raw/$(Version)/build/MSAL.snk" DestinationFolder="$(BaseIntermediateOutputPath)" />
  </Target>

</Project>

2. Add a single C# file with the following content:

namespace Microsoft.Identity.Client
{
    public class DeviceCodeResult
    {
    }
}

3. Add a reference in your project:

<ItemGroup>
  <ProjectReference Include="../Microsoft.Identity.Client/Microsoft.Identity.Client.csproj" />
</ItemGroup>

And that's enough for the dotnet build system to pick the project reference instead of the package reference of the same name, thus reducing the size of Microsoft.Identity.Client.dll from 1 MB to 5 KB.

On macOS, removing the Azure authentication libraries and its dependencies reduces the size of the dlls from 6 MB down to 2.8 MB. In other words, the Azure librarires are responsible fore more than 50% of the size of the Microsoft.Data.SqlClient package.

%%{ init: { 'theme': 'base', 'themeVariables': { 'pie1': 'lightcoral', 'pie2': 'aquamarine' } } }%%
pie title Microsoft.Data.SqlClient composition
  "Azure/authentication libraries" : 3.217
  "SqlClient core libraries" : 2.764

Have a look at the SqlClientSample project in the samples directory for a concrete example.

Advanced configuration

Here are all the MSBuild properties and items supported by Chisel.

ChiselEnabled

defaults to true

In order to completely disable Chisel, set the ChiselEnabled property to false. This can be useful for building on the command line with dotnet build -p:ChiselEnabled=false for example.

ChiselGraphName

defaults to $(MSBuildProjectName).Chisel.mermaid

This is the name of the dependency graph file. A Mermaid file will be written if it ends with either .mmd or .mermaid, otherwise a Graphviz (DOT) file will be written. To completely disable the graph feature, use none.

<PropertyGroup>
  <ChiselGraphName>none</ChiselGraphName>
</PropertyGroup>

Note that the file name must not include a path separator.

ChiselGraphAlias

no default value

Setting the ChiselGraphAlias property adds an alias (link) under the project. This is useful to see the graph directly into the IDE. A very good combination with the Rider Mermaid plugin.

<PropertyGroup>
  <ChiselGraphAlias>Chisel\SqlClientSample.mermaid</ChiselGraphAlias>
</PropertyGroup>

ChiselGraphDirection

defaults to LeftToRight

This defines how the dependency graph is laid out. Possible values are LeftToRight and TopToBottom. Except for shallow graphs, left to right usually produces a more readable graph.

ChiselGraphIncludeVersions

defaults to false

Controls whether the dependency graph nodes are named {package} or {package}/{version}.

Example with ChiselGraphIncludeVersions set to false

graph LR
Serilog.Sinks.File --> Serilog

Example with ChiselGraphIncludeVersions set to true

graph LR
Serilog.Sinks.File/5.0.0 --> Serilog/2.10.0

ChiselGraphIgnore

On real projects, the dependency graph may become huge. Adding packages to ChiselGraphIgnore will remove them from the dependency graph, thus reducing the overall size and increasing readability in other areas.

<ItemGroup>
  <ChiselGraphIgnore Include="Microsoft.Extensions.Configuration" />
  <ChiselGraphIgnore Include="Microsoft.Extensions.DependencyInjection" />
  <ChiselGraphIgnore Include="Microsoft.Extensions.Hosting" />
</ItemGroup>