C#

[DllImport("ntdll.dll", SetLastError = true)]
        public static extern uint ZwQuerySystemInformation(SYSTEM_INFORMATION_CLASS SystemInformationClass, IntPtr SystemInformation, int SystemInformationLength, out int ReturnLength);


        [StructLayout(LayoutKind.Sequential)]
        public struct SYSTEM_HANDLE_INFORMATION
        {
            public int ProcessId; //id of the process whom handle this is
            public byte ObjectTypeNumber; //type of the object
            public byte Flags; // 1 = PROTECT_FROM_CLOSE, 2 = INHERIT
            public short Handle;
            public int Object; //address of the handle
            public int GrantedAccess; //access for the handle
        }

        public const uint STATUS_INFO_LENGTH_MISMATCH = 0xc0000004;

        public static SYSTEM_HANDLE_INFORMATION[] EnumHandles()
        {
            int retLength = 0;
            int handleCount = 0;
            SYSTEM_HANDLE_INFORMATION[] returnHandles;
            int allocLength = 0x1000;
            IntPtr data = Marshal.AllocHGlobal(allocLength);

            // This is needed because ZwQuerySystemInformation with SystemHandleInformation doesn't
            // actually give a real return length when called with an insufficient buffer. This code
            // tries repeatedly to call the function, doubling the buffer size each time it fails.
            while (ZwQuerySystemInformation(SYSTEM_INFORMATION_CLASS.SystemHandleInformation, data,
                allocLength, out retLength) == STATUS_INFO_LENGTH_MISMATCH)
            {
                data = Marshal.ReAllocHGlobal(data, new IntPtr(allocLength *= 2));
            }

            // The structure of the buffer is the handle count plus an array of SYSTEM_HANDLE_INFORMATION
            // structures.
            handleCount = Marshal.ReadInt32(data);
            returnHandles = new SYSTEM_HANDLE_INFORMATION[handleCount];

            for (int i = 0; i < handleCount; i++)
            {
                returnHandles[i] = (SYSTEM_HANDLE_INFORMATION)Marshal.PtrToStructure(
                    new IntPtr(data.ToInt32() + 4 + i * Marshal.SizeOf(typeof(SYSTEM_HANDLE_INFORMATION))),
                    typeof(SYSTEM_HANDLE_INFORMATION));
            }

            Marshal.FreeHGlobal(data);

            return returnHandles;
        }

SYSTEM_HANDLE_INFORMATION[] handles = EnumHandles();
            var winampHandles = from handle in handles
                                where handle.ProcessId == 10004
                                select handle;
            foreach (var winampHandle in winampHandles)
            {
                //do something here...
            }

string openTag = "<upcase>", closeTag = "</upcase>";

string str = "We are living in a <upcase>yellow submarine</upcase>.";

int startIndex = str.IndexOf(openTag);
int endIndex = str.IndexOf(closeTag) + closeTag.Length;

string subStr = str.Substring(startIndex, (endIndex - startIndex));

subStr = subStr.Replace(openTag, "");
subStr = subStr.Replace(closeTag, "");

subStr = subStr.ToUpper();

str = str.Remove(startIndex, (endIndex - startIndex));

str = str.Insert(startIndex, subStr);

private string upperCaseTags(string str, string openTag, string closeTag)
{
    int startIndex;
    while ((startIndex = str.IndexOf(openTag)) != -1)
    {
        int endIndex;
        if ((endIndex = str.IndexOf(closeTag) + closeTag.Length) != -1)
        {
            string subStr = str.Substring(startIndex, (endIndex - startIndex));

            subStr = subStr.Replace(openTag, "").Replace(closeTag, "").ToUpper();

            str = str.Remove(startIndex, (endIndex - startIndex));

            str = str.Insert(startIndex, subStr);
        }
    }
    return str;
}

static void Main(string[] args)
       {
           string str= "19 5456 65";
           string key = "546";
           String encode = Encode(str, key);
           String decode = Encode(encode, key);
           Console.Write(str + "\n" + encode+"\n"+decode);
       }
       static string Encode(string str,string key)
       {
           char []keyChar = key.ToCharArray();
           char[] strChar = str.ToCharArray(); int a = 0;
           for (int i = 0; i < strChar.Length;i++ )
           {
               strChar[i] = (char)(strChar[i] | keyChar[a]);
               a++;
               if (a>keyChar.Length-1)
               {
                   a = 0;
               }
           }
           str = new string(strChar);
           return str;
       }