int pos=1;//定义位置
            Dictionary<int, string> sortedlist = new Dictionary<int, string>() { 
                {1,"one"},
                {2,"two"},
                {3,"three"}
            };
            Dictionary<int, string> sortedlist1 = sortedlist.Take(pos).ToDictionary(c=>c.Key,c=>c.Value);
            sortedlist1.Add(2,"two.one");
            Dictionary<int, string> sortedlist2 = sortedlist.Skip(pos).ToDictionary(c => c.Key+1, c => c.Value);
            Dictionary<int, string> resultlist = sortedlist1.Concat(sortedlist2).ToDictionary(c => c.Key, c => c.Value);
            /*
             * +        [0]    {[1, one]}    System.Collections.Generic.KeyValuePair<int,string>
                +        [1]    {[2, two.one]}    System.Collections.Generic.KeyValuePair<int,string>
                +        [2]    {[3, two]}    System.Collections.Generic.KeyValuePair<int,string>
                +        [3]    {[4, three]}    System.Collections.Generic.KeyValuePair<int,string>

             */