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Old 10-26-2018, 12:13 PM   #1
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Combobox Zombies Puzzle

Here's a little puzzle for anyone interested.
It is based on a similar item posted at the DBGuy's website 3 years ago which he was unable to explain.
As I like riddles(!) I worked out how it was done and am posting a modified version here with his permission.

The attached database contains just 2 objects
a) A table with one record
b) A form with a combo box whose row source is an empty value list



However the combo shows the following items (back from the dead ... so zombies):



Its not too difficult to recover the row source info
BUT can you work out where the combo list info is stored?
Better still can you re-create this scenario in another database?

NOTE: There are no hidden objects or hidden code in this example. It is NOT another security challenge

If you succeed, please send me your solution by private message or email me using the link in my signature line

Please do NOT post your solution in this thread or it will spoil the puzzle for others
Attached Images
File Type: png ComboboxZombies1.PNG (14.5 KB, 569 views)
File Type: png ComboboxZombies2.PNG (31.0 KB, 579 views)
Attached Files
File Type: zip ComboboxZombies.zip (31.5 KB, 117 views)

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Last edited by isladogs; 10-28-2018 at 06:08 PM.
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Old 10-26-2018, 12:53 PM   #2
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Re: Combobox Zombies Puzzle

I'd like to have a look at this, but would need a 2007 version?, sorry.
I cannot open that one.
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Old 10-26-2018, 03:23 PM   #3
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Re: Combobox Zombies Puzzle

Maybe I am missing something here, but when I open it I see in the rowsource
"*";"ABC";"DEF";"GHI";"XYZ"

That is a copy and paste from the row source. So what am I missing?
I am running Access 2016 on Win 10.

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Old 10-26-2018, 04:20 PM   #4
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Re: Combobox Zombies Puzzle

@Gasman
As requested, attached is a 2007 version
It proved tricky to convert - in the end it seemed not to like the button as it used a theme!
Anyway I created & tested it in my A2007 VM.

@MajP
The row source may have got restored when you enabled content.
Try this to recreate the effect

In design view, clear the contents of the combo row source
Save the form.
Close the database
Reopen & it should show the combo list but the row source should (hopefully) be empty

See attached video to see the effect in action
Attached Files
File Type: zip ComboboxZombiesA2007.zip (25.2 KB, 51 views)
File Type: zip ZombieVIDEO.zip (1,006.0 KB, 51 views)
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Old 10-26-2018, 04:34 PM   #5
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Re: Combobox Zombies Puzzle

Seems to depend on how I open it sometimes the row source shows sometimes it does not.
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Old 10-26-2018, 05:03 PM   #6
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Re: Combobox Zombies Puzzle

Quote:
@MajP
The row source may have got restored when you enabled content.
Try this to recreate the effect

In design view, clear the contents of the combo row source
Save the form.
Close the database
Reopen & it should show the combo list but the row source should (hopefully) be empty
That is pretty interesting. I can "break it" to cause it to restore, but cannot figure out where it is coming from.
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Old 10-26-2018, 05:25 PM   #7
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Re: Combobox Zombies Puzzle

Hi MajP
As i wrote in post #1

Quote:
Its not too difficult to recover the row source info
BUT can you work out where the combo list info is stored?
Better still can you re-create this scenario in another database?
The first sentence was to cover the scenario where it sometimes reappears.
I know how to re-create this scenario in a new form / database
In fact I can create a phantom combo list without entering anything on a form.

Interestingly when I was creating a 2007 version for Gasman, I originally just converted it to A2003 MDB.
The zombie effect disappeared!

The original Gremlins DEMO from the DBGuy was part of an old MDB database which he converted to ACCDB.
He wondered if the effect was caused by hitting the limit for the number of objects over the lifetime of a form.
However, I proved that's not the case by re-creating the effect in a new form/database.
In the Gremlins example, you have to do something slightly different to get the rowsource to reappear. See attached
Attached Files
File Type: zip gremlinsdemoORIGINAL.zip (58.5 KB, 51 views)

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Old 10-26-2018, 05:42 PM   #8
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Re: Combobox Zombies Puzzle

My observation so far. The form opens by default when db is opened. Click on combobox to open the dropdown. Switch to design view and will see RowSource list. Close the form. Now open directly to Design View from Nav Pane, nothing in RowSource. Now switch to Form view. Combobox has list. Switch back to Design View, RowSource is still empty.

I can only create new form and combobox with this effect in my db by importing/copying the original table.
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Last edited by June7; 10-26-2018 at 07:12 PM.
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Old 10-27-2018, 02:08 AM   #9
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Re: Combobox Zombies Puzzle

I *think* I know how it is done, but not where they values are stored yet.
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Old 10-29-2018, 10:31 AM   #10
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Re: Combobox Zombies Puzzle

Quote:
Originally Posted by June7 View Post
I can only create new form and combobox with this effect in my db by importing/copying the original table.
Hello all,

I decided to join the forum today, so I can participate in this discussion. I wanted to post a screenshot, but I guess I'm not allowed to do that yet.

In any case, here's a partial quote from my original article on this subject:

Quote:
What do I think is happening?
Here is my speculation on the issue... You know how Microsoft said that a form can only have so much controls added to it over its lifetime? I was wondering how does it keep track of that number? So, my guess as to what's happening with this form is that the Row Source for the combobox is being tracked somehow and stored somewhere that when you change the Row Source Type back to Value List, the original Row Source returns. However, that doesn't explain why the old Row Source still displays even when I manually change the Row Source property.
As it turns out, I was correct in my thinking back then. I didn't say it had to do with the number of controls on the form; but rather, it has something to do with "where" Access is keeping track of certain things, including the Row Source for a Combobox. In fact, this is why I quoted the last poster above because there is a clue in that statement. It "does" have something to do with the original table. So, to recreate this mysterious situation, one has to know how to recreate the original table setup from scratch (or at least understand how it was created in the first place).

Good luck to all!

Just my 2 cents...

DBG
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Old 10-29-2018, 11:32 AM   #11
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Re: Combobox Zombies Puzzle

Hi,

Sorry if this is inappropriate but just checking if I can do a "quick reply" since I tried to post a regular reply earlier but I can't see it now (yet).

Thanks!
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Old 10-29-2018, 12:45 PM   #12
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Re: Combobox Zombies Puzzle

Hi DB Guy

Good to see you at AWF and I hope to see you sharing your wisdom with many more posts here.

You may not have realised that this is a moderated area. Unfortunately, the forum software doesn't alert mods to new posts. As such it gets picked up when one of the moderators notices a new item and I've been offline most of the day.

To speed things up, please report your own post. See sticky above.

New members can only upload files if they are zipped. After 10 posts that restriction is removed. As you have around 73600 posts at UA, hopefully that won't take too long!

EDIT Apologies for misquoting you (re form controls over form lifetime) in post #1. It wasted a fair bit of time on my part following up that point...should have read your blog more carefully!!
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Last edited by isladogs; 10-31-2018 at 02:33 AM.
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Old 10-29-2018, 12:55 PM   #13
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Re: Combobox Zombies Puzzle

Hi Colin,

Thank you for the explanation. I suspected as much and have already started accumulating posts, so I can participate more fully around here. As soon as I have more than 10 posts, I will come back and post the screenshot I mentioned earlier.

Cheers,
DBG


Edit: Okay, as promised, attached is the screenshot of the original article.
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Last edited by theDBguy; 10-29-2018 at 05:35 PM.
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Old 10-29-2018, 01:27 PM   #14
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Re: Combobox Zombies Puzzle

Post 13 was moderated, I'm posting to trigger email notifications.
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Old 10-29-2018, 01:41 PM   #15
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Re: Combobox Zombies Puzzle

Quote:
Originally Posted by Gasman View Post
I *think* I know how it is done, but not where they values are stored yet.
Hi Gasman,

I finally got the real answer from a Microsoft Access engineer as to where this information is stored. I will share it later so as not to spoil this thread for now.

If you want to email me to let me know "how" you think it's done, I'll be happy to give you a hint "where" it is stored (unless of course you figure it out as well).

Good luck!

DBG

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