RpcAnswer.cs

using AltV.Net;

namespace Server.Roleplay.Models;

public class RpcAnswer : IWritable
{
    private readonly IWritable? data;
    private LinkedList<ValidationError>? errors;

    private RpcAnswer(IWritable? data)
    {
        this.data = data;
    }

    private RpcAnswer(ValidationError error)
    {
        errors = new(new[] { error });
    }

    public static RpcAnswer Fail(ValidationError error)
    {
        return new RpcAnswer(error);
    }

    public static RpcAnswer Ok(IWritable? value = default)
    {
        return new RpcAnswer(value);
    }

    public void OnWrite(IMValueWriter writer)
    {
        writer.BeginObject();
        if (errors is { Count: > 0 })
        {
            writer.Name("errors");
            writer.BeginArray();
            foreach (var error in errors)
            {
                error.OnWrite(writer);
            }
            writer.EndArray();
        }
        if (data is not null)
        {
            writer.Name("data");
            writer.Value(data);
        }
        writer.EndObject();
    }

    public RpcAnswer Error(ValidationError error)
    {
        errors ??= new();
        errors.AddLast(error);
        return this;
    }
}

ValidationError.cs

using AltV.Net;

namespace Server.Roleplay.Models;

public class ValidationError : IWritable
{
    public string Name { get; set; }
    public string Code { get; set; }

    public ValidationError(string name, string code)
    {
        Name = name;
        Code = code;
    }

    public void OnWrite(IMValueWriter writer)
    {
        writer.BeginObject();
        writer.Name("name");
        writer.Value(Name);
        writer.Name("code");
        writer.Value(Code);
        writer.EndObject();
    }
}