Egothor.Stemmer.Diff.Apply C# (CSharp) Method

        public static void Apply(StringBuilder dest, string diff)
        {
            try
            {

                if (diff == null)
                {
                    return;
                }

                int pos = dest.Length - 1;
                if (pos < 0)
                {
                    return;
                }
                // orig == ""
                for (int i = 0; i < diff.Length / 2; i++)
                {
                    char cmd = diff[2 * i];
                    char param = diff[2 * i + 1];
                    int par_num = (param - 'a' + 1);
                    switch (cmd)
                    {
                        case '-':
                            pos = pos - par_num + 1;
                            break;
                        case 'R':
                            dest[pos] = param;
                            break;
                        case 'D':
                            int o = pos;
                            pos -= par_num - 1;
                            /*
                             * delete par_num chars from index pos
                             */
                            // String s = orig.toString();
                            // s = s.substring( 0, pos ) + s.substring( o + 1 );
                            // orig = new StringBuffer( s );
                            dest.Remove(pos, (o + 1) - pos);
                            break;
                        case 'I':
                            dest.Insert(pos += 1, param);
                            break;
                    }
                    pos--;
                }
            }
            catch (IndexOutOfRangeException /*x*/)
            {
                // x.printStackTrace();
            }
            catch (ArgumentOutOfRangeException /*x*/)
            {
                // x.printStackTrace();
            }
        }

 private static void AssertTrie(Trie trie, string file, bool usefull,
                                bool storeorig)
 {
     using (TextReader @in =
                new StreamReader(new FileStream(file, FileMode.Open), Encoding.UTF8))
     {
         for (string line = @in.ReadLine(); line != null; line = @in.ReadLine())
         {
             try
             {
                 line = line.ToLowerInvariant();
                 StringTokenizer st = new StringTokenizer(line);
                 st.MoveNext();
                 string stem = st.Current;
                 if (storeorig)
                 {
                     string cmd = (usefull) ? trie.GetFully(stem) : trie
                                  .GetLastOnPath(stem);
                     StringBuilder stm = new StringBuilder(stem);
                     Diff.Apply(stm, cmd);
                     assertEquals(stem.ToLowerInvariant(), stm.ToString().ToLowerInvariant());
                 }
                 while (st.MoveNext())
                 {
                     string token = st.Current;
                     if (token.Equals(stem, StringComparison.Ordinal))
                     {
                         continue;
                     }
                     string cmd = (usefull) ? trie.GetFully(token) : trie
                                  .GetLastOnPath(token);
                     StringBuilder stm = new StringBuilder(token);
                     Diff.Apply(stm, cmd);
                     assertEquals(stem.ToLowerInvariant(), stm.ToString().ToLowerInvariant());
                 }
             }
             catch (InvalidOperationException /*x*/)
             {
                 // no base token (stem) on a line
             }
         }
     }
 }