System.Collections.Specialized.StringDictionary.ContainsKey C# (CSharp) Method

        public virtual bool ContainsKey(string key) { throw null; }
        public virtual bool ContainsValue(string value) { throw null; }

        public Arguments(string[] args)
        {
            _params = new StringDictionary();
            Regex spliter = new Regex(@"^-{1,2}|^/|=|:", RegexOptions.IgnoreCase | RegexOptions.Compiled);
            Regex remover = new Regex(@"^['""]?(.*?)['""]?$", RegexOptions.IgnoreCase | RegexOptions.Compiled);

            string parm = null;
            string[] parts;

            foreach (var a in args)
            {
                parts = spliter.Split(a, 3);
                switch (parts.Length)
                {
                    case 1:
                        if (parm != null)
                        {
                            if (!_params.ContainsKey(parm))
                            {
                                parts[0] = remover.Replace(parts[0], "$1");
                                _params.Add(parm, parts[0]);
                            }
                            parm = null;
                        }
                        break;
                    case 2:
                        if (parm != null)
                        {
                            if (!_params.ContainsKey(parm))
                                _params.Add(parm, "true");
                        }
                        parm = parts[1];
                        break;
                    case 3:
                        if (parm != null)
                        {
                            if (!_params.ContainsKey(parm))
                                _params.Add(parm, "true");
                        }
                        parm = parts[1];
                        if (!_params.ContainsKey(parm))
                        {
                            parts[2] = remover.Replace(parts[2], "$1");
                            _params.Add(parm, parts[2]);
                        }

                        parm = null;
                        break;
                }
            }

            if (parm != null)
            {
                if (!_params.ContainsKey(parm))
                    _params.Add(parm, "true");
            }
        }