Hi Jean,
Sorry for the inconvenience caused.
We have tested the reported issue but we are unable to reproduce the issue. Could you please check the below sample?
Sample:
http://www.syncfusion.com/downloads/Support/DirectTrac/85868/TreeGridBinding-1328606145.zip Below code is showing exact width of the Tree Columns,
treeGrid.InternalGrid.Columns[index].Width
If you still face any difficulties means, could you please modify our sample based on your need and revert us with replication procedure, that would be very helpful to serve you better.
Please let us know if you have any queries.
Thanks,
Rajasekar