AnyGenerator.md

🧩 AnyGenerator — Custom Union Type Generator

The MultiType.NET.Generator package enables you to define your own custom union types using a simple [GenerateAny] attribute. It removes boilerplate and auto-generates rich union logic for your own domain-specific types.

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⚙️ What It Does

• Generates a struct based on your type definition.
• Implements all core APIs: Match, TryMatch, Map, Switch, From, TryFrom, and more.
• Adds optional System.Text.Json support for serialization.
• Integrates seamlessly with Controllers, Minimal APIs, and DTOs.

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🚀 How to Use

1️⃣ Install the Generator Package

dotnet add package MultiType.NET.Generator

2️⃣ Annotate Your Partial Struct

[GenerateAny(typeof(int), typeof(string))]
public partial struct IntOrString;

3️⃣ Use It Like Any<T1, T2>

IntOrString value = "hello";

var result = value.Match(
    i => $"Int: {i}",
    s => $"String: {s}"
);

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✨ Advanced Example

[GenerateAny(typeof(Success), typeof(Warning), typeof(Error), typeof(Info))]
public partial struct StatusType
{
    public static StatusType From(string value) => value.ToLowerInvariant() switch
    {
        "success" => new Success(),
        "warning" => new Warning(),
        "error" => new Error(),
        "info" => new Info(),
        _ => throw new ArgumentException("Invalid status")
    };

    public bool IsSuccess => this.Is<Success>();
    public bool IsWarning => this.Is<Warning>();
    public bool IsError => this.Is<Error>();
    public bool IsInfo => this.Is<Info>();

    public readonly struct Success { }
    public readonly struct Warning { }
    public readonly struct Error { }
    public readonly struct Info { }
}

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📤 JSON Support

The generated type is automatically decorated to support System.Text.Json Without any manual changes.

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// Generates a discriminated union of int, string, or Guid
[GenerateAny(typeof(int), typeof(string), typeof(Guid))]
public partial struct Payload;

// POST endpoint accepting Payload from body
[HttpPost("submit-payload")]
public async Task<IActionResult> SubmitPayload(
    [FromBody] Payload payload)
{
    // payload.Match(...)
    return Ok();
}

// GET endpoint accepting Payload from query
[HttpGet("search")]
public async Task<IActionResult> SearchPayload(
    [FromQuery] Payload query)
{
    return Ok();
}

✅ Use Cases

Use Case	Example
API Payloads	IntOrString for flexible IDs
Workflow Status	StatusType for state modeling
Dynamic Input	StringOrBoolOrInt from forms or query strings

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📎 Notes

• Generated files are .g.cs and automatically included during compilation.
• Works with source generators (no runtime reflection).
• Types must be readonly struct.

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📘 Next Step

➡️ Proceed to CLI Generator for generating Any<T1..T50> and custom JSON converters.