Tuesday, October 04, 2005

Blank page when setting a tabcontrol's tabpage by its index

I am working on an application that has 30-40 tabs in a tab control. To keep it reasonable for the user, I need to limit the displayed tabs to just the 4-5 tabs that are relevant to the current action.

First I tried the obvious of just setting the visible property of the unwanted tabpages to false. This hid the contents of the tabpage, but the tabpage itself remained visible and in the row of tabs that could be selected by the user. If the tabpage had fully hidden itself as it should have (in my mind), I would have been all set. But instead I had a problem to solve.

To clarify, I have almost 40 tabpages total in the tabcontrol. There are four tabpages that always should be shown in a particular order (tabpages 2-5) and I wanted the first tabpage on the left to be different and selected depending on which item was selected in a tree control on the form.

In other words, I want all 40 tabs on the tabcontrol for ease of maintenance on the form, but to only show 5 of those tabpages at any time and to be able to dynamically change which tabpage from the non-display tabpages was to be shown at the first tabpage, depending on what is selected on a tree control on the form.

The first issue was that I could not insert a tabpage to a certain position. The .add method only adds the tabpage to the end of the existing tabpages collection.

The second issue was that any direct assignment to a tabpage always produced a blank tabpage, i.e., none of its child controls were visible and all attempts to get them to appear failed. That was disappointing as I could have just added a dummy tabpage as the first one and then repeatedly replaced with with the tabpage of current interest as the user moved around the tree control.

Utilimately I created a second non-visible tab control on the form named tcHidden, moved all the tabs over to it at Form_Load, then moved the tabpages between the two controls in the desired order as the user moved around in the tree control. It works well and it is fast enough that the users are happy with it.

The tabcontrol is one of those controls that seems to give me fits, probably because I always try to push it to its limits, so I wanted to post one of my workarounds in case someone else has a similar need. If you found this helpful, please post a comment and let me know. Thanks.

Note that I am using Visual Basic .Net 2003 and Framework v1.1

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