Simple URL builder for C#

UrlBuilder.cs

//+ Jonas Raoni Soares Silva
//@ http://raoni.org

using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;

namespace JonasRaoni
{
    class UrlBuilder
    {
        private readonly string _path;
        private readonly NameValueCollection _queryCollection = HttpUtility.ParseQueryString(string.Empty);

        public UrlBuilder(string path) => _path = path;


        [UsedImplicitly]
        public UrlBuilder AddQueryParam(string name, string? value)
        {
            if (string.IsNullOrEmpty(name))
            {
                throw new ArgumentException("Value cannot be null or empty.", nameof(name));
            }

            if (string.IsNullOrEmpty(value))
            {
                return this;
            }

            _queryCollection.Add(name, value);
            return this;
        }


        public override string ToString()
        {
            var query = _queryCollection.ToString();
            return string.IsNullOrEmpty(query) ? _path : $"{_path}?{query}";
        }
    }

    static class UrlBuilderExtensions
    {
        public static UrlBuilder AddQueryParam<T>(this UrlBuilder builder, string name, IEnumerable<T>? values)
        {
            if (values != null)
            {
                foreach (var value in values)
                {
                    builder.AddQueryParam(name, value?.ToString());
                }
            }

            return builder;
        }

        public static UrlBuilder AddQueryParam(this UrlBuilder builder, string name, IEnumerable<long?>? values)
        {
            foreach (var value in values ?? Enumerable.Empty<long?>())
            {
                builder.AddQueryParam(name, value?.ToString(CultureInfo.InvariantCulture));
            }

            return builder;
        }

        public static UrlBuilder AddQueryParam(this UrlBuilder builder, string name, IEnumerable<decimal?>? values)
        {
            foreach (var value in values ?? Enumerable.Empty<decimal?>())
            {
                builder.AddQueryParam(name, value?.ToString(CultureInfo.InvariantCulture));
            }

            return builder;
        }

        public static UrlBuilder AddQueryParam(this UrlBuilder builder, string name, bool? value)
        {
            builder.AddQueryParam(name, value?.ToString());

            return builder;
        }

        public static UrlBuilder AddQueryParam(this UrlBuilder builder, string name, Enum? value)
        {
            builder.AddQueryParam(name, value?.ToString());

            return builder;
        }

        public static UrlBuilder AddQueryParam(this UrlBuilder builder, string name, decimal? value)
        {
            builder.AddQueryParam(name, value?.ToString(CultureInfo.InvariantCulture));

            return builder;
        }

        public static UrlBuilder AddQueryParam(this UrlBuilder builder, string name, long? value)
        {
            builder.AddQueryParam(name, value?.ToString(CultureInfo.InvariantCulture));

            return builder;
        }

        public static UrlBuilder AddQueryParam(this UrlBuilder builder, string name, DateTimeOffset? value)
        {
            if (value != null)
            {
                builder.AddQueryParam(name, value.Value.ToUniversalTime().ToString("s", CultureInfo.InvariantCulture) + "Z");
            }

            return builder;
        }
    }
}