+20翻转字符.
static   void   Main(string[]   args) 
 		{ 
 			string   m=null; 
 			string   str   =    "hello   world ";			 
 			char[]   chars   =   str.ToCharArray();   
 	                                                      foreach(char   j   in   chars) 
 			{  				          
 				            m+=j;  					 
 			} 
 			System.Console.WriteLine( "{0} ",m); 
 		} 
 我想让程序输出:dlrow   olleh 
 不想用Array.Reverse 
------解决方案--------------------try   
 string m = string.Empty; 
 string str =  "hello world "; 
 StringBuilder sb = new StringBuilder(); 
 for (int i = str.Length - 1; i > = 0; i--) 
 { 
     sb.Append(str[i]); 
 } 
 m = sb.ToString(); 
 System.Console.WriteLine( "{0} ", m);
------解决方案--------------------static void Main(string[] args) 
         { 
             string m = null; 
             string str =  "hello world "; 
             char[] chars = str.ToCharArray();   
             for (int i=chars.Length-1;i> =0;i--) 
             {   
                 m += chars[i];   
             } 
             System.Console.WriteLine( "{0} ", m);   
         } 
------解决方案--------------------string str =  "hello world "; 
          string temp =  " "; 
          for(int i = 0; i <str.Length;i++) 
              temp += str[str.Length - 1 - i]; 
          Console.WriteLine(temp);
------解决方案--------------------string str =  "hello world "; 
 			string revStr = string.Empty; 
 			for (int i= str.Length-1; i> =0; i--) 
 			{ 
 				revStr += str[i]; 
 			} 
 			Console.WriteLine(revStr);
------解决方案--------------------private string StringReverse(string inStr) 
         { 
             string temp = string.Empty; 
             int length = inStr.Length; 
             for (int i = 0; i  < (length / 2); ++i) 
             { 
                 temp = inStr[i]; 
                 inStr[i] = inStr[length - i - 1]; 
                 inStr[length - i - 1] = temp; 
             } 
             return inStr; 
         }
------解决方案--------------------用VB 库的 StrReverse 颠倒字符串位置   
 .NET  可以   
     Function StringReverse(ByVal s As String, Optional ByVal stringIndex As Integer = 0, Optional ByVal count As Integer = -1) 
         Dim chars() As Char = s.ToCharArray() 
         If count  < 0 Then count = s.Length - stringIndex 
         Array.Reverse(chars, stringIndex, count) 
         Return New String(chars) 
     End Function