Automatic extension method generation for easy updating of existing class instances

Proposal

I’m loving the library, but I think it would be very helpful to have the source generator automatically create extension methods for the updating of existing class instances. This would allow classes to become more “record-like”, allowing updates in-place.

I’m proposing here that the “lifting” method to be called BuildNew(), but I dont think this is ideal, and I think a better name should be thought of. I would call it With(), but that conflicts with the current WithX naming convention of the existing builders.

Example API:

[AutoGenerateBuilder(generateSetters: true)]
public class User
{
    public string Name { get; set; }
    public string Gender { get; set; }
}

...

var user = await dbContext.Users.FirstAsync();

user.BuildNew() // `BuildNew` originates from an auto-generated extension method class in UserBuilder.g.cs. Lifts user into a UserBuilder
    .WithName("New Name") // usual updates happen here
    .Build(); // Updates the object in-place.

// OPTIONALLY if generateSetter == True

user.SetName("Newer Name"); // Sets the name

await dbContext.SaveChangesAsync(); // user's Name property is updated.

// also allow for operations on items in a collection
var users = dbContext.Users.Where(x => x.Gender == "Male").ToListAsync();

users.SetGender("Female") // Updates all elements in-place. Could also use `BuildNew()` syntax.

dbContext.SaveChangesAsync();

I feel like this is a natural continuation of the current library. It appears like you’re supposed to be able to use UsingInstance for this purpose to update existing instances in-place, but I can’t get it to work. This would also bring existing non-record classes to be more “record like”.

[StefH]

Official NuGet will be released shorty.

[Meigs2]

@StefH I’ve given it a test, looks great! Appreciate it.