string S = "２００８年０１月３０日";
for (int i = 0; i <= 9; i++)
    S = S.Replace((char)((ushort)'０' + i), (char)((ushort)'0' + i));

------解决方案--------------------
[code=C#][/code]  /**//// <summary>

       /// 转全角的函数(SBC case)

       /// </summary>

       /// <param name="input">任意字符串</param>

       /// <returns>全角字符串</returns>

       ///<remarks>

       ///全角空格为12288，半角空格为32

       ///其他字符半角(33-126)与全角(65281-65374)的对应关系是：均相差65248

       ///</remarks>       

       public string ToSBC(string input)

       {

           //半角转全角：

           char[] c=input.ToCharArray();

           for (int i = 0; i < c.Length; i++)

           {

               if (c[i]==32)

               {

                   c[i]=(char)12288;

                   continue;

               }

               if (c[i]<127)

                   c[i]=(char)(c[i]+65248);

           }

           return new string(c);               

       }





       /**//// <summary>

       /// 转半角的函数(DBC case)

       /// </summary>

       /// <param name="input">任意字符串</param>

       /// <returns>半角字符串</returns>

       ///<remarks>

       ///全角空格为12288，半角空格为32

       ///其他字符半角(33-126)与全角(65281-65374)的对应关系是：均相差65248

       ///</remarks>

       public string ToDBC(string input)

       {   

           char[] c=input.ToCharArray();

           for (int i = 0; i < c.Length; i++)

           {

               if (c[i]==12288)

               {

                   c[i]= (char)32;

                   continue;

               }

               if (c[i]>65280 && c[i]<65375)

                   c[i]=(char)(c[i]-65248);

           }   

           return new string(c);

       }



------解决方案--------------------
string str = "２２１４２３４１２３４１２";
StringBuilder sb = new StringBuilder();
foreach(Char ch in str.ToCharArray())
{
   if(Char.IsDigit(ch))
   {
       switch(ch)
       {
   case '１':  
       sb.Append(1);
       break;
   case '２':
       sb.Append(2);
       break;
   case '３':  
       sb.Append(3);
       break;
   case '４':
       sb.Append(4);
       break;
   case '５':  
       sb.Append(5);
       break;
   case '６':  
       sb.Append(6);
       break;
   case '７':
      sb.Append(7);
       break;
   case '８':  
       sb.Append(8);
       break;
   case '９':
       sb.Append(9);
       break;
   case '０':
       sb.Append(0);
       break;
   default:
       sb.Append(ch);
       break;
}
   }
}
string sss = sb.ToString();