Dictionary: как правильно описать свойство set {} - C#

    public class A
    {
        string value1;
        string valuse2;
        public A()
        {
            value1 = "aaa";
            valuse2 = "ббб";
        }
 
        public Dictionary<string, string> d
        {
            get
            {
                var dic = new Dictionary<string, string>
                {
                    {"val1", value1},
                    {"val2", valuse2}
                };
 
                return dic;
            }
            set
            {
                
            }
        }
    }