char[] c;
string s = "a12121afdafadfdsd";
c = s.ToCharArray();
for (int i = 1; i < c.Length-1; i++) {
    c[i] = '*';
}
Response.Write(new string(c));

------解决方案--------------------
C# code

using System;
using System.Collections.Generic;
using System.Text;

namespace Csharp_Test_Code
{
    class Run
    {
        static void Main()
        {
            string str = GetString("sas");
        }

        static string GetString(string str)
        {
            if (str.Length <= 2)
            {
                return str;
            }
            StringBuilder sb = new StringBuilder();
            sb.Append(str[0]);
            char c = str[str.Length - 1];
            sb.Append('*', str.Length - 2);
            sb.Append(c);
            return sb.ToString();
        }
    }
}

------解决方案--------------------
C# code

string c = null; 
c = "abcde"; 
c = string.Format("*{0}*", Strings.Mid(c, 2, Strings.Len(c) - 2));

------解决方案--------------------

引用楼主 mimi1002 的帖子:

还有一个问题就是如何获取本页的完整的url