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I have a problem with NULL (Blank()) values in Gallery+Form application; Dropdown component

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Posted on by VictorSotnikov

I have a typical canvas App that has a Gallery. Its data source is a table of SQL Server. The gallery is editable. We can change a field New Patient directly in the Gallery; it is available as Dropdown:

The Allowed Values are [Blank(), "Y", "N"] in App. The corresponding column in the DB table is NULLable.

A user also can open a Form (for a selected Gallery row) and modify the field New Patient there (as a Dropdown component):

I have met a problem when the field has NULL (blank) value. The scenario is the following:

I am in the Gallery. There is a row where the New Patient field is “Y”:

I change the dropdown value to blank. Then I look at the DB table and see – yes, the corresponding row has acquired value NULL, as expected.

Then I open the Form and see that the New Patient field displays value Y, not blank.

Then I (without modifying anything in the Form) close the Form; and open it again. Now the New Patient field has blank value, as expected. In other words, the Form has shown the correct (blank) value in the dropdown only after the Form was re-opened.

Why the Form did not show blank value in the field the first time; why it shows the blank value only after it was re-opened? Should I call some Reset() or anything like this somewhere?

I can add that I see the same behavior in the both situation when the App is run: when I do Preview or when I do Play (of a published version).

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Building Power Apps

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RandyHayes 76,297 Super User 2024 Season 1 on at

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@VictorSotnikov

What is the Items property of your Gallery and the Item property of your form?

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VictorSotnikov 75 on at

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“What is the Items property of your Gallery” – it is a complicated one:

….
SortByColumns(Filter('data.VisitType', te_DataSourceKey_Filter.Text in DataSourceKey, te_VisitType_Filter.Text in VisitType, If(IsBlank(te_IsNewPatient_Filter.Text),true,te_IsNewPatient_Filter.Text in isNewPatient)) ,varSortPriority,If(SortDescending,Ascending,Descending))
….

The 'data.VisitType' is the data source (corresponds to the SQL table). The te_DataSourceKey_Filter etc are text fields that play role of a filter. The varSortPriority is a session variable with sorting column name. The SortDescending is a session variable that contains either true or false.

“the Item property of your form?” – it is the following: gl_Type.Selected. The gl_Type is the Gallery component name.

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RandyHayes 76,297 Super User 2024 Season 1 on at

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@VictorSotnikov

Not too complex, although you can simplify a little with:

SortByColumns( Filter('data.VisitType', te_DataSourceKey_Filter.Text in DataSourceKey, te_VisitType_Filter.Text in VisitType, IsBlank(te_IsNewPatient_Filter.Text) || (te_IsNewPatient_Filter.Text in isNewPatient) ), varSortPriority, If(SortDescending,Ascending,Descending) )

This just primarily removes the If statement in the formula - which should be avoided!

Next, I need to know your terminology. You stated - "close the Form; and open it again" Does this mean that you display the EditForm in your app again, or that you close the App and then reopen it?

You also stated - "The gallery is editable" does this mean that you are performing the edits in a Gallery or in the EditForm (or both)? (I assume both based on your further description)

How are you updating that to your datasource in the Gallery?

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VictorSotnikov 75 on at

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“…Does this mean that you display the EditForm in your app again, or that you close the App and then reopen it?...” – this means that I open the EditForm in my app again.

“You also stated - "The gallery is editable" does this mean that you are performing the edits in a Gallery or in the EditForm (or both)? (I assume both based on your further description)” - yes, I am performing the edits in both the Gallery and EditForm. But in the given error scenario I did not do any real edit in the EditForm; I did not modify any component. I just saw that the Dropdown does not display the expected blank value – and immediately closed the EditForm; then immediately opened it again.
BTW, here is the code that works in the EditForm when I click Close button:

Event: OnSelect; Code: ResetForm(Form1);Back()

Please ask more details if you need them.

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VictorSotnikov 75 on at

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I have found the following solution:
in OnSelect event of the button that opens the Form I do the following:

EditForm(Form1);
Navigate(VisitTypeForm, ScreenTransition.None);
ResetForm(Form1);

Do you have any comment on that?

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