With.Fody

With.Fody copied to clipboard

This is an add-in for Fody

A Fody addin to extend immutable C# classes with With() methods to return a copy of an object with one field modified.

Introduction to Fody.

The nuget package

https://nuget.org/packages/With.Fody/

PM> Install-Package With.Fody

Your Code

public class MyClass
{
    public MyClass(int intValue, string stringValue, OtherClass c1, OtherClass c2)
    {
        this.IntValue = intValue;
        this.StringValue = stringValue;
        this.C1 = c1;
        this.C2 = c2;
    }

    public int IntValue { get; }

    public string StringValue { get; }

    public OtherClass C1 { get; }

    public OtherClass C2 { get; }

    // Needed for IntelliSense/Resharper support
    public MyClass With<T>(T value) => this;

    // If two properties have same type, we need to append the property name to With
    public MyClass WithC1(OtherClass value) => this;
    public MyClass WithC2(OtherClass value) => this;

    // We can make an explicit version of With for multiple parameters
    public MyClass With(int intValue, string stringValue) => this;

    // Method name can be more explicit, and parameter names should match property names
    public MyClass WithC1andC2(OtherClass c1, OtherClass c2) => this;
}

What gets compiled

public class MyClass
{
    public MyClass(int intValue, string stringValue, OtherClass c1, OtherClass c2)
    {
        this.IntValue = intValue;
        this.StringValue = stringValue;
        this.C1 = c1;
        this.C2 = c2;
    }

    public int IntValue { get; }

    public string StringValue { get; }

    public OtherClass C1 { get; }

    public OtherClass C2 { get; }

    public MyClass With(int value)
    {
        return new MyClass(value, this.StringValue, this.C1, this.C2);
    }

    public MyClass With(string value)
    {
        return new MyClass(this.IntValue, value, this.C1, this.C2);
    }

    // If two properties have same type, we need to append the property name to With
    public MyClass WithC1(OtherClass value)
    {
        return new MyClass(this.IntValue, this.StringValue, value, this.C2);
    }

    public MyClass WithC2(OtherClass value)
    {
        return new MyClass(this.IntValue, this.StringValue, this.C1, value);
    }

    public MyClass With(int intValue, string stringValue)
    {
        return new MyClass(intValue, stringValue, this.C1, this.C2);
    }

    public MyClass WithC1andC2(OtherClass c1, OtherClass c2)
    {
        return new MyClass(this.IntValue, this.StringValue, c1, c2);
    }
}

Motivation

The motivation behind this plugin is explained in the post Tweaking immutable objects with C# and Fody.

Icon

Icon created by Yazmin Alanis from Noun Project