AutoComplete (Using the IAutoComplete interface)

This project is intended to demonstrate how to implement the IAutoComplete interface to VB6.

It provides more features than the "SHAutoComplete" API.

For example to determine whether the drop-down list is dropped down or not.
But the most important feature is that you can define custom sources. (by a simple string array)

At design time (IDE) there is only one dependency. (AutoCompleteGuids.tlb)
But for the compiled .exe there are no dependencies, because the .tlb gets then compiled into the executable.

Notes:
- There is no way to uninitialize the autocomplete object. You can only disable it. Setting the autocomplete object to nothing has therefore no effect and is not recommended. Anyhow, the autocomplete object will be automatically uninitialized when the TextBox (or any other edit control) receives the WM_DESTROY message.
- Use modeless forms to enable the user to use the mouse on the drop-down suggest list as else only keyboard inputs will work on modal forms.

List of revisions:

Code:

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23-Feb-2026
- Included enum AutoCompleteOptionRightToLeft.
16-Apr-2025
- Ready for 64-bit.
- Modified AutoCompleteGuids.tlb. (compiled with same uuid)
  Unregister to old AutoCompleteGuids.tlb is not necessary, just overwrite the file.
06-Nov-2018
- Use of lightweight COM object IEnumString in AutoCompleteHandle.bas.
- Modified AutoCompleteGuids.tlb. (compiled with same uuid)
  Unregister to old AutoCompleteGuids.tlb is not necessary, just overwrite the file.
29-Dec-2013
- Enhancement of the Disable and Enable method.
13-Aug-2013
- Fixed a bug that the application will crash when there is an empty string in the custom source.
12-Aug-2013
- First release.

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I've searched and searched for a solution to the custom lists issue but got nothing but a sniff with some C++ code on planet source code. I didn't understand the C++ code and I don't understand much of your vb6 code yet but you seem to have cracked it; well done! (so far...)
Re. you comment 'The option flag 'AutoCompleteOptionUseTab' is not working when using the intrinsic VB TextBox control' can you expand on/ describe that fault at more length.

Quote:

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Originally Posted by Magic Ink

Re. you comment 'The option flag 'AutoCompleteOptionUseTab' is not working when using the intrinsic VB TextBox control' can you expand on/ describe that fault at more length.

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The autocomplete object is subclassing the TextBox control.
When the option flag 'AutoCompleteOptionUseTab' is set it watches for a tab key on the WM_KEYDOWN message.
But the problem is that the intrinsic VB TextBox cannot trap the tab key. (Only when all control's TabStop properties are false; but that is not an option).

This limitation can be solved when using a control that can trap such keys.
For example in the TextBoxW control of my common controls project. There is a PreviewKeyDown event to solve this issue.

Code:

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Private Sub TextBoxW1_PreviewKeyDown(ByVal KeyCode As Integer, IsInputKey As Boolean)
If KeyCode = vbKeyTab Then IsInputKey = TestAutoComplete.DroppedDown()
End Sub

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The ESC key can also be included. The autocomplete object notice this and closes the list without any activation of "Cancel" CommandButtons.

Code:

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Private Sub TextBoxW1_PreviewKeyDown(ByVal KeyCode As Integer, IsInputKey As Boolean)
If KeyCode = vbKeyTab Or KeyCode = vbKeyEscape Then IsInputKey = TestAutoComplete.DroppedDown()
End Sub

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Thanks for that, and for info on the Esc key which was going to be the subject of my next question.

You may also include the Enter key (vbKeyReturn). Resulting that any "Default" CommandButton will not be fired when selecting an item from the drop-down list with the Enter key.

Or another way: Allow the "Default" CommandButton to be fired when pressing Enter and trap the Enter key to inform the autocomplete object that the Enter key was pressed. (for correct behavior)
But this solution is only necessary when there is any "Default" CommandButton on the form as else the enter key will be already treated as an input key.

Code:

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Private Sub TextBoxW1_PreviewKeyDown(ByVal KeyCode As Integer, IsInputKey As Boolean)
If KeyCode = vbKeyTab Or KeyCode = vbKeyEscape Or KeyCode = vbKeyReturn Then IsInputKey = TestAutoComplete.DroppedDown()
End Sub

' The Call (or any other logic) should be within the KeyDown event and not in the PreviewKeyDown
' Do this only when there is any "Default" CommandButton.
Private Sub TextBoxW1_KeyDown(KeyCode As Integer, Shift As Integer)
If KeyCode = vbKeyReturn Then Call CommandDefault_Click
End Sub

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this is a very good attempt to handle the topic 'AutoComplete'.

Concerning the way to uninitialize the autocomplete object ..

The provided sub '.disable' is not working properly.
It looks like that the "SHAutoComplete - API" is still active. (You could reproduce the situation very simple after a couple of inputs (and Key Down's))

The SHAutoComplete - API could be disabled via the flag '&H20000000'.
If you fire this flag with the api (SHAutoComplete) on the hwnd .. autocomplete is 100% dead.
After this .. there is no way to turn it on again.
Destroying the 'Autocomplete' (set to nothing / re .INIT) is not working properly as mentioned.

In order to allow "toggle" at runtime .. 2 Textboxes are required. (-> Solution: Usercontrol)
Is there a simple way to trigger the WM_DESTROY message - although the control is not destroyed? :confused:

:thumb: I appreciate your work here in the forum.

Quote:

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Originally Posted by adix

The provided sub '.disable' is not working properly.

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I can't replicate the problem. When I use the sub '.Disable' the drop-down list is not anymore dropping down. The reference is indeed not terminated, only "disabled". That's why when you use the sub '.Enable' then it is like you never called '.Disable'.

The Sub '.disable' is not 100% working .. when the type is FileSystem. (autocomplete list still pops up .. after a couple of folder - Inputs)
A proper solution is to reset the options to 'AutoCompleteOptionNone' while you disable the autocomplete

.Options = AutoCompleteOptionNone

Now the Autocomplete works like a charm. Thank you

[
I've enhanced the AutoComplete.cls Enable / Disable Sub's.

(Disable -> Backup current .options / set to None / Disable)
(Enable -> Restore Options / Enable)
]

I dont think that the used IE or shlwapi.dll is important.
I could reproduce the effect on my primary Dev-Environment [Win XP SP3 (running within a VMWare instance)] and on my physical W7 / W8 Environments.

Quote:

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Originally Posted by adix

The Sub '.disable' is not 100% working .. when the type is FileSystem. (autocomplete list still pops up .. after a couple of folder - Inputs)
A proper solution is to reset the options to 'AutoCompleteOptionNone' while you disable the autocomplete

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Update released.
Thanks

hello, your Project is perfect, but in usercontrol keydow not work, not select in list, only mouse, do you know how do it

Update released.

Use of lightweight COM object IEnumString.
Minor modification in TLB. (uuid the same; just replace file)

Now only the first character can be used. Is there a way to drop down the list when entering any one character?

Quote:

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Originally Posted by ChenLin

Now only the first character can be used. Is there a way to drop down the list when entering any one character?

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What you mean with only first character? You can also drop down by code ".DroppedDown = True" or by key arrow down in the edit control.

For example, the word Format, now only the input F will display the result, I mean to enter O or M, or any letter of the Format will display the result.

Quote:

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Originally Posted by ChenLin

For example, the word Format, now only the input F will display the result, I mean to enter O or M, or any letter of the Format will display the result.

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And before the change to lightweight COM it was other or what?

I think ChenLin means that typing a single "O" should also jump to "Format" because of the "o" in it.
But that's more a search function, not autocomplete.

Autocomplete works as the following (to my knowledge!)

Assuming the following auto complete list

• Aqua
• Black
• Blue
• Brown
• Red

If you type "B" the list scrolls to "Black"
If then type "R" (giving the sequence "BR") the lists scrolls to "Brown"

Updated the demo and included the enum AutoCompleteOptionRightToLeft.

A new (better) approach to handle PreviewKeyDown event is to send WM_GETDLGCODE message and check the return value.
IAutoComplete will subclass that message and alter the return values for certain keys.
The benefit is that the flag 'AutoCompleteOptionUseTab' will determine whether DLGC_WANTTAB is returned or not. Thus the code is more dynamic. Of course DLGC_WANTTAB is not returned when the drop-down list is hidden.
For the return and escape key we still just check for DroppedDown().

Code:

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Private Sub TextBoxW1_PreviewKeyDown(ByVal KeyCode As Integer, IsInputKey As Boolean)
Select Case KeyCode
    Case vbKeyTab
        Const WM_GETDLGCODE As Long = &H87, DLGC_WANTTAB As Long = &H2
        IsInputKey = CBool((SendMessage(TextBoxW1.hWnd, WM_GETDLGCODE, KeyCode, ByVal 0&) And DLGC_WANTTAB) = DLGC_WANTTAB)
    Case vbKeyReturn, vbKeyEscape
        If Not TestAutoComplete Is Nothing Then IsInputKey = TestAutoComplete.DroppedDown()
End Select
End Sub

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Quote:

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Originally Posted by Krool

This project is intended to demonstrate how to implement the IAutoComplete interface to VB6.

It provides more features than the "SHAutoComplete" API.

For example to determine whether the drop-down list is dropped down or not.
But the most important feature is that you can define custom sources. (by a simple string array)

At design time (IDE) there is only one dependency. (AutoCompleteGuids.tlb)
But for the compiled .exe there are no dependencies, because the .tlb gets then compiled into the executable.

Notes:
- There is no way to uninitialize the autocomplete object. You can only disable it. Setting the autocomplete object to nothing has therefore no effect and is not recommended. Anyhow, the autocomplete object will be automatically uninitialized when the TextBox (or any other edit control) receives the WM_DESTROY message.
- Use modeless forms to enable the user to use the mouse on the drop-down suggest list as else only keyboard inputs will work on modal forms.

List of revisions:

Code:

---

23-Feb-2026
- Included enum AutoCompleteOptionRightToLeft.
16-Apr-2025
- Ready for 64-bit.
- Modified AutoCompleteGuids.tlb. (compiled with same uuid)
  Unregister to old AutoCompleteGuids.tlb is not necessary, just overwrite the file.
06-Nov-2018
- Use of lightweight COM object IEnumString in AutoCompleteHandle.bas.
- Modified AutoCompleteGuids.tlb. (compiled with same uuid)
  Unregister to old AutoCompleteGuids.tlb is not necessary, just overwrite the file.
29-Dec-2013
- Enhancement of the Disable and Enable method.
13-Aug-2013
- Fixed a bug that the application will crash when there is an empty string in the custom source.
12-Aug-2013
- First release.

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Excellent work! :)
Thank you Krool!!!