AutoPatcher 1.0.2

AutoPatcher

Lightning fast automatic model patching using Optional types and source generation. Compatible with System.Text.Json.

Installation

• For the source generator, Optional types and its System.Text.Json converter:

dotnet add package AutoPatcher

The source generator is not included in the other packages, so if you need it, you have to install this package first.

• For ASP.NET Core:

dotnet add package AutoPatcher.AspNetCore

• Data annotations for Optional<T> (already included if you're using the ASP.NET Core package):

dotnet add package AutoPatcher.DataAnnotations

• For just the Optional<T> type and its System.Text.Json converter (already included in every other package):

dotnet add package AutoPatcher.Core

Basic usage

Given the following models

using AutoPatcher;

namespace People;

public class Person
{
    public int Id { get; init; }
    public string Name { get; set; }
    public int Age { get; set; }
}

public class UpdatePersonModel
{
    public Optional<string> Name { get; set; }
    public Optional<int> Age { get; set; }
}

You can patch Person with

var person = ...; // Get person from somewhere
var model = new UpdatePersonModel { Name = "Jake" };

// Do some manual mapping
if (model.Name.HasValue) person.Name = model.Name.Value;
if (model.Age.HasValue) person.Age = model.Age.Value;

Automatic patching

Writing a lot of ifs can be cumbersome and tricky to mantain. This is where automatic patching comes in handy.

To get started, annotate the model with optional properties with [PatchModel(typeof(...))] where typeof(...) points to the target type.

using AutoPatcher;

[PatchModel(typeof(Person))] // <--
public class UpdatePersonModel
{
    public Optional<string> Name { get; set; }
    public Optional<int> Age { get; set; }
}

AutoPatcher will then generate the following Patch extension method for you

public static void Patch(this UpdatePersonModel model, Person target)
{
    if (model.Name.HasValue) target.Name = model.Name.Value;
    if (model.Age.HasValue) target.Age = model.Age.Value;
}

Now let's update our code to use our new extension method

var person = ...; // Get person from somewhere
var model = new UpdatePersonModel { Name = "Jake" };
model.Patch(person);

AutoPatcher also handles nested PatchModels and lists (and lists of PatchModels!).

Usage with ASP.NET Core

Configure AutoPatcher on your Startup or WebApplicationBuilder

// MVC, Controllers, Razor Pages
services.AddControllers().AddAutoPatcher();

// Minimal APIs
services.AddAutoPatcherJsonOptions();

You can now use Optionals on your ASP.NET Core application.

Data annotations

The default data annotations, like [StringLength(...)] or [Email], do not work for Optionals. Don't worry though! AutoPatcher.DataAnnotations adds Optional-friendly alternatives for the annotations you know and love.

using AutoPatcher;
using AutoPatcher.DataAnnotations;

[PatchModel(typeof(Person))]
public class UpdatePersonModel
{
    [OptionalStringLength(250)]
    public Optional<string> Name { get; set; }

    [Range(18, 200)]
    public Optional<int> Age { get; set; }
}

A note on Source generators

Source generators can be tricky sometimes, in case your IDE is not picking up a generated Patch method, a quick IDE restart (or refresh on VS Code) should do the trick.

Usually, even if you're getting squigglies, dotnet build or your IDE's Run command should still work normally.