#region 刪除重復字符 
string s = "sdfffffsrlkjesgljfdg03940864e5=_0R9DTGR98YUI//|||'//???fdf///"; 
Response.Write("<br/>String：" + s + "<br/>Result："); 
IEnumerable<char> distinctList = s.Distinct(); 
foreach (char a in distinctList) 
{ 
    Response.Write(a.ToString()); 
} 
 
//使用移除法 
for (int i = 0; i < s.Length; i++) 
{ 
    while (s.IndexOf(s.Substring(i, 1)) != s.LastIndexOf(s.Substring(i, 1))) 
    { 
        s = s.Remove(s.LastIndexOf(s.Substring(i, 1)), 1); 
    } 
} 
Response.Write("<hr/>Result：" + s); 
#endregion