test.cs

public static class TextControlExtensions {
  public static int Load(this ServerTextControl serverTextControl,
                         LoadSettings ls,
                         byte[] data,
                         int iterator = 0) {
    try {

      // check format based on first 4 bytes
      if (iterator == 0) {
        var test = data.Take(4);

        foreach (var hintFormat in HintFormats) {
          if (test.SequenceEqual(hintFormat.Value)) {
            iterator = hintFormat.Key;
            break;
          }
        }
      }

      switch (iterator) {
        case 0:
          serverTextControl.Load(data, BinaryStreamType.WordprocessingML, ls);
          return 1024;

        case 1:
          serverTextControl.Load(data, BinaryStreamType.MSWord, ls);
          return 64;

        case 2:
          serverTextControl.Load(data, BinaryStreamType.AdobePDF, ls);
          return 512;

        case 3:
          serverTextControl.Load(Encoding.UTF8.GetString(data), 
                                 StringStreamType.RichTextFormat, ls);
          return 8;

        case 4:
          serverTextControl.Load(Encoding.UTF8.GetString(data), 
                                 StringStreamType.HTMLFormat, ls);
          return 4;

        case 5:
          serverTextControl.Load(data, 
                                 BinaryStreamType.InternalUnicodeFormat, ls);
          return 32;

        case 6:
          serverTextControl.Load(data, 
                                 BinaryStreamType.SpreadsheetML, ls);
          return 4096;
      }
    }
    catch (MergeBlockConversionException) { }
    catch {
      if (iterator != 6) {
        iterator++;
        return Load(serverTextControl, ls, data, iterator);
      }
    }

    return 0;
  }

  private static readonly Dictionary<int, byte[]> HintFormats =
    new Dictionary<int, byte[]> {
      [0] = new byte[] { 80, 75, 3, 4 }, // WordProcessingML
      [1] = new byte[] { 208, 207, 17, 224 }, // MSWord
      [2] = new byte[] { 37, 80, 68, 70 }, // AdobePDF
      [3] = new byte[] { 123, 92, 114, 116 }, // RichTextFormat
      [5] = new byte[] { 8, 7, 1, 0 } // InternalUnicodeFormat
  };
}