AngleSharp by Florian Rappl

<PackageReference Include="AngleSharp" Version="0.9.1" />

.NET API 1,208,832 bytes

 CssDocumentRule

Contains the rules specified by a @document { /* ... */ } rule.
using AngleSharp.Css; using AngleSharp.Parser.Css; using System.Collections.Generic; namespace AngleSharp.Dom.Css { internal sealed class CssDocumentRule : CssGroupingRule, ICssDocumentRule, ICssConditionRule, ICssGroupingRule, ICssRule, IStyleFormattable { private readonly List<CssDocumentFunction> _conditions; public string ConditionText { get { string[] array = new string[_conditions.Count]; for (int i = 0; i < array.Length; i++) { array[i] = _conditions[i].ToCss(); } return string.Join(", ", array); } set { List<CssDocumentFunction> list = base.Parser.ParseDocumentRules(value); if (list == null) throw new DomException(DomError.Syntax); _conditions.Clear(); _conditions.AddRange(list); } } public List<CssDocumentFunction> Conditions => _conditions; internal CssDocumentRule(CssParser parser) : base(CssRuleType.Document, parser) { _conditions = new List<CssDocumentFunction>(); } protected override void ReplaceWith(ICssRule rule) { base.ReplaceWith(rule); CssDocumentRule cssDocumentRule = rule as CssDocumentRule; _conditions.Clear(); _conditions.AddRange(cssDocumentRule._conditions); } public override string ToCss(IStyleFormatter formatter) { string rules = formatter.Block(base.Rules); return formatter.Rule("@document", ConditionText, rules); } } }