The Code

The new version of the HelpReader.Net uses the following libraries
  • HTML Help Library by Klaus Weisser – See
  • OpenNetCF Library for the HTML Viewer Control - See
  • SharpZipLib Library included (required by HtmlHelp Library) See

I also ported from ‘C’ into ‘C#’ the CHMLib library by Jed Wing.

A Big thank you to these guys for releasing there code so we can all benefit from it. Thanks.

There are a number of points to make here concerning the porting of the CHMLib. Firstly, when porting LZW decompression code, I had to first compile the code in ‘C’ and get the pre-processor to export the source sent to the compiler. This is because the original code used a lot of macros which made it very difficult to see how to port come sections of the code. Once I had this source I could port the code to C#. I had to convert all the buffer accesses to use .Net Streams, along with the code which read buffers. This included creating special classes with hold the data from the internal structures of the CHM File Stream, and manually reading the data from the CHM file into the data members of the class. (Using BinaryReader.ReadUInt16 etc).

Once I had a version which compiled in C#, I then had to test that the code worked. This was a case of running both versions of the library side by side in 2 instances of Visual Studio 2003 and extracting files from the same CHM file, making source that the output was the same.

Once done, I replaced the base stream handling used by the HTML Help library with the ported library, and then had a working CHM Reader which could extract files, extract help indexes & perform searches using the HTML Help library.

The HelpReader

Now that I had the basics working, I then when on to develop the Reader it’s self. Once you have the filename of the page you want to display (From the Index, Contents or search) you can then extract that file from the Help file. This file then as to be scanned, and the images, frame pages & Style Sheets used by the HTML page need to be extracted, and the HTML patched so that they point to the new location of the files. In this case a temp directory in the filing system. Also at this point I remove XML and Script tags as they are not supported. Once this is done I can then save the file, and use the OpenNetCF library’s HTML Viewer control to view the page as intended.

There is more to it that what I have described, so look that the code. The code is not optimized as yet. This is some that may or may not get done depending on time.

If you can not read a Help File, please debug the code and post any changes, If you really can not get the Help file to view, then please email me with the Help file.

I hope you enjoy this version.

Last edited Jun 17, 2008 at 11:14 AM by PJTewkesbury, version 2


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