AutoCtor 2.0.0-alpha.3

AutoCtor

AutoCtor is a Roslyn Source Generator that will automatically create a constructor for your class for use with constructor Dependency Injection.

NuGet packages

https://nuget.org/packages/AutoCtor/

Usage

Your code

[AutoConstruct]
public partial class ExampleClass
{
    private readonly IService _service;
}

What gets generated

partial class ExampleClass
{
    public ExampleClass(IService service)
    {
        _service = service;
    }
}

More Features

Post constructor Initialisation

If you include the name of a method to call after the fields are set, it will be called in the constructor. This method must return void.

[AutoConstruct(nameof(Initialize))]
public partial class NamedPostConstruct
{
    private readonly IService _service;

    private void Initialize()
    {
    }
}

partial class NamedPostConstruct
{
    public NamedPostConstruct(IService service)
    {
        _service = service;
        Initialize();
    }
}

Alternatively, you can mark the method to call at the end of the method with the [AutoPostConstruct] attribute.

[AutoConstruct]
public partial class PostConstructMethod
{
    private readonly IService _service;

    [AutoPostConstruct]
    private void Initialize()
    {
    }
}

partial class PostConstructMethod
{
    public PostConstructMethod(IService service)
    {
        _service = service;
        Initialize();
    }
}

Post constructor methods can also take parameters. These parameters will be passed in from the constructor.

public partial class PostConstructMethodWithParameters
{
    private readonly IService _service;

    [AutoPostConstruct]
    private void Initialize(IInitialiseService initialiseService)
    {
    }
}

partial class PostConstructMethodWithParameters
{
    public PostConstructMethodWithParameters(IService service, IInitialiseService initialiseService)
    {
        _service = service;
        Initialize(initialiseService);
    }
}

More examples

You can also initialize readonly fields, and AutoCtor will not include them in the constructor.

[AutoConstruct]
public partial class ClassWithPresetField
{
    private readonly IService _service;
    private readonly IList<string> _list = new List<string>();
}

partial class ClassWithPresetField
{
    public ClassWithPresetField(IService service)
    {
        _service = service;
        // no code to set _list
    }
}

If there is a single base constructor with parameters, AutoCtor will include that base constructor in the constructor it creates.

public abstract class BaseClass
{
    protected IAnotherService _anotherService;

    public BaseClass(IAnotherService anotherService)
    {
        _anotherService = anotherService;
    }
}

[AutoConstruct]
public partial class ClassWithBase : BaseClass
{
    private readonly IService _service;
}

partial class ClassWithBase
{
    public ClassWithBase(IAnotherService anotherService, IService service) : base(anotherService)
    {
        _service = service;
    }
}

Embedding the attributes in your project

By default, the [AutoConstruct] attributes referenced in your project are contained in an external dll. It is also possible to embed the attributes directly in your project. To do this, you must do two things:

1. Define the MSBuild constant AUTOCTOR_EMBED_ATTRIBUTES. This ensures the attributes are embedded in your project.
2. Add compile to the list of excluded assets in your <PackageReference> element. This ensures the attributes in your project are referenced, insted of the AutoCtor.Attributes.dll library.

Your project file should look like this:

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

  <PropertyGroup>
    
    <DefineConstants>AUTOCTOR_EMBED_ATTRIBUTES</DefineConstants>
  </PropertyGroup>

  
  <PackageReference Include="AutoCtor"
                    PrivateAssets="all"
                    ExcludeAssets="compile;runtime" />


</Project>

Preserving usage of the [AutoConstruct] attribute

The [AutoConstruct] attributes are decorated with the [Conditional] attribute, so their usage will not appear in the build output of your project. If you use reflection at runtime you will not find the [AutoConstruct] attributes.

If you wish to preserve these attributes in the build output, you can define the AUTOCTOR_USAGES MSBuild variable.

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

  <PropertyGroup>
    
    <DefineConstants>AUTOCTOR_USAGES</DefineConstants>
  </PropertyGroup>

  
  <PackageReference Include="AutoCtor" PrivateAssets="all" />

</Project>

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