Build 4.0.0.28 of xlsgen adds XLSB template mode. This template mode means you can open an existing XLSB file, make a few changes and save it back preserving everything including objects that xlsgen does not support yet in the API, for instance smart art (also known as diagrams). XLSB is now a first class citizen. After support for importing XLSB files, and saving to XLSB files, it was the next logical step but the dots had to be connected, and it was no easy task to keep everything in context and sometimes re-map and re-contextualize objects, all of which cannot be done without a powerful core runtime.

This template mechanism also works for buffers in memory rather than files.

Scenarios such as migrating XLS or XLSX files (and their variants) to XLSB files also take advantage of this feature to avoid losing objects. And vice versa, from XLSB files to XLSX files.

Build 4.0.0.27 of xlsgen adds support for table parts in XLSB files. Table parts include column name and definition, style as well as custom formulas (i.e. calculated columns). This is to be in par with what xlsgen was doing so far for XLSX files.

Build 4.0.0.26 adds support for expressions such as Table1[[#This Row];[Y2013]:[Y2016]] in the formula parser, as well as for migrating to and from XLSX and XLSB files.

xlsgen 4.0.0.25 of xlsgen rearchitects itself in the area related to styles, named styles, their management (duplication, enforcing) in order to be as neutral as possible with Excel. This is a work for XLSX and XLSB files.

Build 4.0.0.24 of xlsgen adds round-trip support to font features such as the associated theme (minor or major) as well as the alpha channel for colors (transparency level in objects supporting this feature). This is for XLSX and XLSB files (and their variants).

Build 4.0.0.23 of xlsgen fixes the parser used in common expressions in formulas with COUNTIF()/SUMIF() and AVERAGEIF(). The expression to compare to was not supporting all operator cases, and all operand cases, which could return in the calculation engine unable to compute the value in such a cell.