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jed76
Post Prodigy
Post Prodigy

ComboBox IsEmpty not working?

I can't understand what I'm doing wrong here:

 

I'd like a ComboBox to either be visible or not (or I could use DisplayMode.Edit / DisplayMode.View) if another ComboBox is empty. However, it doesn't seem to work and even when I use:

 

If(!IsEmpty(ComboBox1.Selected),DisplayMode.View,DisplayMode.Edit) for the DisplayMode of the other ComboBox, it still seems to think that there is some content in the ComboBox even when it is actually blank / empty? This means the other ComboBox remains in VIEW mode even when the other box is blank?

1 ACCEPTED SOLUTION

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RandyHayes
Super User
Super User

@jed76 

@poweractivate 

 

.Selected is VERY viable on a ComboBox.  It is not Deprecated.  I believe you are thinking of SelectedText which IS deprecated and should be avoided.

 

But, Selected is absolutely usable and HAS to be used in many cases.  If you want to know what item is selected in your ComboBox...how else would you do it?  That is what .Selected is for.

 

Selected returns the selected record in your ComboBox.

SelectedItems returns the table of records selected IF you have multiple selections turned on.

 

DefaultSelectedItems is an input property to the combobox, so you cannot check it in a formula.

 

Like ALL controls that have an Items property as an Input, any output will present either a record or a table of records based on the schema of the Items property records.

 

SO...whatever columns you have in your Items property are what you would check in your formula.

The column you check is completely dependent on the schema of the Items property records!

 

If you had an Items property that was just ["A", "B", "C"] then this would represent a table with a Value column...and then Selected.Value would be what to check.

 

@jed76 

Your original formula is using IsEmpty.  This function is well misunderstood as it is a function to test if a record or table is empty.  And by empty, I mean nothing!

For example:  IsEmpty(Table()) is true whereas IsEmpty(Table({})) is false

This is because the second one has a record in it.  Technically it is all empty (to us), but to the IsEmpty function, it has something and is not empty.

So, when trying to do the IsEmpty function on a schema based table that is found in a SelectedItems it will always return false

Bottom-line...it is NOT the function you want to use to test with in this case.

 

IsBlank is what you want!

 

Your formula should be:

If(!IsBlank(ComboBox1.Selected.Value), DisplayMode.View, DisplayMode.Edit)

(using the .Value here based on prior comments...again, replace with the appropriate column from your items schema)

 

You could also use:

If(CountRows(ComboBox1.SelectedItems)>0, DisplayMode.View, DisplayMode.Edit)

 

Note, the first is looking at a record from the combobox.  Selected will ALWAYS represent the record of the last selected item of the control.  

SelectedItems is used in the second formula in which case (again, IsEmpty will not work on it) we use the CountRows to countrows of the table.

 

Hopefully this all makes sense and is helpful.

 

 

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30 REPLIES 30
poweractivate
Super User
Super User

@jed76 

 

You should not use Selected for ComboBox

 

use SelectedItems instead, and do not use the Selected property of a Combo Box control, if possible

 

Try this instead:

 

//untested - adjust as needed
If(!IsEmpty(ComboBox1.SelectedItems),DisplayMode.View,DisplayMode.Edit)

 

 

or this (but the above is better):

 

//untested - adjust as needed
If(!IsBlank(First(ComboBox1.SelectedItems)),DisplayMode.View,DisplayMode.Edit)

 

 

Also, note:

 

IsEmpty is for a Table

IsBlank is for a single Record

 

and you should not use Selected property for ComboBox

use SelectedItems property instead for ComboBox

 

------------

NOTE:

Although the below may still work with Selected, I do not recommend it and I think it is deprecated

Spoiler
//DO NOT USE THIS, NOT RECOMMENDED
If(!IsBlank(ComboBox1.Selected),DisplayMode.View,DisplayMode.Edit)
//don't use it - this might stop working in the future
//and you shouldn't use the Selected property of a ComboBox
//use SelectedItems or DefaultSelectedItems instead

I do not recommend using Selected property of ComboBox, I think it is actually deprecated and may stop working in the future

 

poweractivate
Super User
Super User

@jed76 

 

Don't use Selected for a ComboBox.

Use either DefaultSelectedItems or SelectedItems

 

In your case, you probably want SelectedItems

 

see if it helps @jed76 

RandyHayes
Super User
Super User

@jed76 

@poweractivate 

 

.Selected is VERY viable on a ComboBox.  It is not Deprecated.  I believe you are thinking of SelectedText which IS deprecated and should be avoided.

 

But, Selected is absolutely usable and HAS to be used in many cases.  If you want to know what item is selected in your ComboBox...how else would you do it?  That is what .Selected is for.

 

Selected returns the selected record in your ComboBox.

SelectedItems returns the table of records selected IF you have multiple selections turned on.

 

DefaultSelectedItems is an input property to the combobox, so you cannot check it in a formula.

 

Like ALL controls that have an Items property as an Input, any output will present either a record or a table of records based on the schema of the Items property records.

 

SO...whatever columns you have in your Items property are what you would check in your formula.

The column you check is completely dependent on the schema of the Items property records!

 

If you had an Items property that was just ["A", "B", "C"] then this would represent a table with a Value column...and then Selected.Value would be what to check.

 

@jed76 

Your original formula is using IsEmpty.  This function is well misunderstood as it is a function to test if a record or table is empty.  And by empty, I mean nothing!

For example:  IsEmpty(Table()) is true whereas IsEmpty(Table({})) is false

This is because the second one has a record in it.  Technically it is all empty (to us), but to the IsEmpty function, it has something and is not empty.

So, when trying to do the IsEmpty function on a schema based table that is found in a SelectedItems it will always return false

Bottom-line...it is NOT the function you want to use to test with in this case.

 

IsBlank is what you want!

 

Your formula should be:

If(!IsBlank(ComboBox1.Selected.Value), DisplayMode.View, DisplayMode.Edit)

(using the .Value here based on prior comments...again, replace with the appropriate column from your items schema)

 

You could also use:

If(CountRows(ComboBox1.SelectedItems)>0, DisplayMode.View, DisplayMode.Edit)

 

Note, the first is looking at a record from the combobox.  Selected will ALWAYS represent the record of the last selected item of the control.  

SelectedItems is used in the second formula in which case (again, IsEmpty will not work on it) we use the CountRows to countrows of the table.

 

Hopefully this all makes sense and is helpful.

 

 

_____________________________________________________________________________________
Digging it? - Click on the Thumbs Up below. Solved your problem? - Click on Accept as Solution below. Others seeking the same answers will be happy you did.
NOTE: My normal response times will be Mon to Fri from 1 PM to 10 PM UTC (and lots of other times too!)
Check out my PowerApps Videos too! And, follow me on Twitter @RandyHayes

Really want to show your appreciation? Buy Me A Cup Of Coffee!
jed76
Post Prodigy
Post Prodigy

@RandyHayes 

 

As always - a thorough and very helpful response. Thank you very much! I’ll give your suggestions a try.

 

Thank you!!

poweractivate
Super User
Super User

@RandyHayes 

 

I really like this explanation, however I was still not sure whether or not the Selected property of a Combo Box control in particular, might be internally scheduled for eventual future deprecation

and if so that it should not be used, and here is why I might suspect this:

 

Since there are cases where a Combo Box may allow multiple selections, then using the Selected property would be ambiguous, because it would result in only one Record (when I checked, it works, but it picked the very last selection, though I am not sure exactly what selection it picks, whether it's the first one, last one, or even just arbitrary). In this case, the expected behavior might be for it to get all the Records, in some points of view.

 

That's not what I necessarily think the expected behavior of Selected should be, I think it's behaving fine.

 

However, if someone were to use that property Selected for a Combo Box in particular, they might get confused about the behavior of why only one Record is being returned and not a Table. In other words, perhaps some people might wonder, why is there a property Selected of a Combo Box which returns just one Record, when a Combo Box may have one or more Records - and if there are multiple records, how are they supposed know which of the selections will be chosen if they use the Selected property of a Combo Box?

 

The obvious answer is not to use Selected when your Combo Box allows multiple selections, as it would result in an unexpected outcome. 

 

However, SelectedItems can be used predictably and consistently with a Combo Box control in both cases - with one selection, or multiple selections.

 

Instead, whether it's only one Record or multiple Records, SelectedItems is more consistent. When there's only one Record, then just use

 

//example formula - change ComboBoxControl to the actual name of your Combo Box control
First(ComboBoxControl.SelectedItems)

 

When the destination requires a Record and not a Table, they should get an error in the formula, so they will have to change the formula to use only one of the Combo Box selections explicitly, such as by using First.

 

However, Selected will not give any error, it will just pick one of the multiple selections. Some people may wonder, why would there be a property which would have an unexpected outcome in the case of multiple selections? Also, some people may wonder, Selected returns only one Record - does that mean - a Combo Box always returns one Record too? It might introduce ambiguity in even what a Combo Box is and whether it returns one Record or a Table from some points of view.

 

I personally don't really have an issue with this, however, I believe that in some points of view, this type of situation is considered problematic, specifically that: when multiple Records are expected from a Combo Box (i.e. a Table) why is there a built in property that returns just one of them (i.e. a Record), whether it's the first one, last one, or an arbitrary one?

 

I also noticed that the property Selected of a Combo Box control is missing entirely from the relevant official Microsoft documentation page.

In case this was not a mistake, it may mean that the property is internally being scheduled for eventual deprecation. I am aware it could be a mistake, however, I am actually unsure it is a mistake in this case, I think there is a chance that the Selected property of a Combo Box might be intentionally missing from the documentation in this case.

 

I suspect it could be because of what I described, and thus, the Selected property of a Combo Box control in particular might be internally scheduled for eventual deprecation for the reasons I described in this post.

 

The use of property Selected is not consistent with the principle that while a Combo Box may have only one selection, and often does in many cases, (such as when the SharePoint List data source's Choice column  does not have Allow multiple selections toggled to Yes in the settings, and the default setting if not explicitly changed, is indeed No, so often it's just one selection in the Combo Box control that uses this column) but that it may also have multiple selections in some cases.

 

The Selected property on a Combo Box control introduces ambiguity on what Record is returned in the case that the Combo Box does have multiple selections. 

 

I wanted to know if @v-jefferni , @v-bofeng-msft , or @v-xiaochen-msft could please clarify on this. Specifically, to clarify on:

 

1. Is it a mistake or is it intentional that the property Selected of a Combo Box control is missing entirely from the relevant official Microsoft documentation page

 

2. If it is intentional that the property Selected of a Combo Box control is missing from that page, is it because the Selected property of a Combo Box  might be internally scheduled for eventual future deprecation?

 

3. If the Selected property of a Combo Box  might be internally scheduled for eventual future deprecation, might it be partially because of what I just described in this post, potentially among other reasons?

 

4. If the Selected property of a Combo Box  might be internally scheduled for eventual future deprecationdespite what @RandyHayes says being a very strong explanation (I really like it a lot personally), that maybe it is actually not a good idea to be encouraging anyone to continue to use the Selected property of a Combo Box and in that case, would it be better to go with my advice instead to simply not use the Selected property of a Combo Box and instead to use SelectedItems in all such cases, even for returning just one Record ?

So:

 

//example formula - change ComboBoxControl to the actual name of your Combo Box control
First(ComboBoxControl.SelectedItems)

 

for cases where it is known that there is going to be only one selected item in the Combo Box?

 

5. If it actually was a mistake that the Selected property of a Combo Box control is missing from that page, could it be clarified which Record is returned exactly, when using the  Selected property of a Combo Box control that allows multiple selections - is it always the first Record, the last Record, or is it not predictable at all which Record is returned?

 

I wanted to know if the above could be clarified so I could have the correct understanding.

 

Thanks!

@RandyHayes  Just tried this and it works a treat.....

 

*****IGNORE - I have just figured it out by using an OR statement set to check for "ThisItem.<columnName" !IsEmpty as well. Many thanks. *******

 

However. When the gallery writes back to the SP list, I have the ComboBox's Default Selected Items to show "ThisItem.<Column Name in SP List>". How can I also use this value as well so that the other ComboBox is in VIEW mode only? For example, when I am populating the boxes, it works a treat. However, when I return the gallery after the items have been patched back to the SP list, the combobox returns a FALSE again since it is now displaying its default seleced item, if you see what I mean?

 

Many thanks. 

@jed76 


@jed76 wrote:

... when I return the gallery after the items have been patched back to the SP list, the combobox returns a FALSE again since it is now displaying its default seleced item, if you see what I mean?

 

Many thanks. 


For that check if below two threads help you identify this potential specific issue:

Combo box auto populated data not working with Patch or in email

Combo Box Selected Items - Lookup Field Issues 

 

 

poweractivate
Super User
Super User

@jed76 

 

First, check your Form's Item property (if it's a Form). Is it set to the Record you want?

If it's not a Form, or if you are sure it is correct, then:

 

Check the Gallery you are referring to. Do you mean that the Combo Box is a Control that is inside the Gallery? If so, check the DisplayMode of the Combo Box - is it set to DisplayMode.View? Whether it is or not though, a value should still be populating in there if you have  DefaultSelectedItems correctly set of that same Combo Box (which it seems like you do to me).

 

Otherwise, you have already indicated that you might have DefaultSelectedItems correctly set

(but check it once more just in case).

and if so,

Check those two threads I gave

especially the first one Combo box auto populated data not working with Patch or in email  

as that may help you identify your issue.

 

See if it helps @jed76 


@jed76 wrote:

@RandyHayes  Just tried this and it works a treat.....

 

*****IGNORE - I have just figured it out by using an OR statement set to check for "ThisItem.<columnName" !IsEmpty as well. Many thanks. *******

I see you might have resolved your issue now, glad you were able to resolve it 🙂

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