c# windows form store global data

Using the following Class, you can store somethings you need cross forms.
Pretty handy sometimes instead of using Setting in C#. Setting creates visible config file
and it's pretty slow to read and write.

class GlobalData
    {
        private static GlobalData _instance = new GlobalData();
        private string _formString = "";

        static GlobalData()
        {
        }

        public static GlobalData GetInstance()
        {
            return _instance;
        }

        public string TokenString
        {
            get
            {
                return _formString;
            }
            set
            {
                _formString = value;
            }
        }
    }