Попробуйте
List<Dictionary<string, string>> listDic = new List<Dictionary<string, string>>();
Dictionary<string, string> dic = new Dictionary<string, string>();
Dictionary<string, string> dic1 = new Dictionary<string, string>();
dic.Add("key1", "value1");
dic1.Add("key2", "value2");
listDic.Add(dic);
listDic.Add(dic1);