readme.source.md

AutoCtor

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

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NuGet packages

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

Usage

Your code

snippet: Basic

What gets generated

snippet: BasicGeneratedCode

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More Features

Post constructor Initialisation

You can mark a method to be called at the end of the constructor with the attribute [AutoPostConstruct]. This method must return void.

snippet: PostConstruct

snippet: PostConstructGeneratedCode

Keyed Services

When using Microsoft.Extensions.DependencyInjection you can mark fields and properties with [AutoKeyedService] and it will be included in the constructor.

snippet: KeyedService

snippet: KeyedServiceGeneratedCode

Initialize with parameters

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

snippet: PostConstructWithParameters

snippet: PostConstructWithParametersGeneratedCode

Initialize readonly fields with ref or out

If a parameter is marked ref or out and matches the type of a readonly field, it can set that field during construction.

snippet: PostConstructWithOutParameters

snippet: PostConstructWithOutParametersGeneratedCode

Argument Guards

Null guards for the arguments to the constructor can be added in 2 ways.

In your project you can add a AutoCtorGuards property.

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

  <PropertyGroup>
    <AutoCtorGuards>true</AutoCtorGuards>
  </PropertyGroup>

</Project>

In each AutoConstruct attribute you can add a setting to enable/disable guards.

snippet: Guards

snippet: GuardsGeneratedCode

Property Initialisation

AutoCtor can set properties that are considered as read only properties.

snippet: PropertyExamples

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More examples

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

snippet: PresetField

snippet: PresetFieldGeneratedCode

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

snippet: Inherit

snippet: InheritGeneratedCode

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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, instead of the AutoCtor.Attributes.dll library.

Your project file should look like this:

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

  <PropertyGroup>
    <!--  Define the MSBuild constant    -->
    <DefineConstants>AUTOCTOR_EMBED_ATTRIBUTES</DefineConstants>
  </PropertyGroup>

  <!-- Add the package -->
  <PackageReference Include="AutoCtor"
                    PrivateAssets="all"
                    ExcludeAssets="compile;runtime" />
<!--                               ☝ Add compile to the list of excluded assets. -->

</Project>

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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>
    <!--  Define the MSBuild constant    -->
    <DefineConstants>AUTOCTOR_USAGES</DefineConstants>
  </PropertyGroup>

  <!-- Add the package -->
  <PackageReference Include="AutoCtor" PrivateAssets="all" />

</Project>

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