Evaluate escaped string

Question

I have some strings in a file that are already escaped. So the content of the file looks like this:

Hello\\nWorld. This is\\tGreat.

When I

Answer 1

based on @deAtog 's code, i made some minor additions

• support \U00000000 format chars

• simplify the hex conversions somewhat

  string UnEscape(string s)
  {
      StringBuilder sb = new StringBuilder();
      Regex r = new Regex("\\\\[abfnrtv?\"'\\\\]|\\\\[0-3]?[0-7]{1,2}|\\\\u[0-9a-fA-F]{4}|\\\\U[0-9a-fA-F]{8}|.");
      MatchCollection mc = r.Matches(s, 0);
  
      foreach (Match m in mc)
      {
          if (m.Length == 1)
          {
              sb.Append(m.Value);
          }
          else
          {
              if (m.Value[1] >= '0' && m.Value[1] <= '7')
              {
                  int i = Convert.ToInt32(m.Value.Substring(1), 8);
                  sb.Append((char)i);
              }
              else if (m.Value[1] == 'u')
              {
                  int i = Convert.ToInt32(m.Value.Substring(2), 16);
                  sb.Append((char)i);
              }
              else if (m.Value[1] == 'U')
              {
                  int i = Convert.ToInt32(m.Value.Substring(2), 16);
                  sb.Append(char.ConvertFromUtf32(i));
              }
              else
              {
                  switch (m.Value[1])
                  {
                      case 'a':
                          sb.Append('\a');
                          break;
                      case 'b':
                          sb.Append('\b');
                          break;
                      case 'f':
                          sb.Append('\f');
                          break;
                      case 'n':
                          sb.Append('\n');
                          break;
                      case 'r':
                          sb.Append('\r');
                          break;
                      case 't':
                          sb.Append('\t');
                          break;
                      case 'v':
                          sb.Append('\v');
                          break;
                      default:
                          sb.Append(m.Value[1]);
                          break;
                  }
              }
          }
      }
  
      return sb.ToString();
  }