I have this formula as part of a combobox items property:-

    Distinct(colRelatedPostingUnPostingForms, 'Location Name') As v, v.Value in ShowColumns(Filter(Locations,
    StreetTitleSync in ShowColumns(PostingFormStreetComboBox.SelectedItems,"Title")),"Title"))

the idea is that i only want to show the Location Name for the selected Streets from the PostingFormStreetComboBox... but currently i am getting that the ShowColumns has some invalid arguments.. any advice?

2 Answers 2


This is a characteristic of forms in Power Apps canvas apps. While generally you can reference a control's .SelectedItems property in such scenarios, you can't if the control happens to be in a form card. As a workaround, you should use ClearCollect in the control's OnChange to temporarily store the values in a collection. The collection will be accepted in your ShowColumns expression.


See: https://powerusers.microsoft.com/t5/Building-Power-Apps/ShowColumns-DropColumns-based-on-ComboBox-SelectedItems-or/td-p/867702

In PowerApps, ShowColumns is used to create a new table with only the specified columns from an existing table. It expects a table as its first argument and one or more column names as subsequent arguments.

You’re trying to use ShowColumns to filter a table based on the selected items in a ComboBox, which is not its intended use. Use filter

    Distinct(colRelatedPostingUnPostingForms, 'Location Name') As v, 
    v.Value in Filter(Locations, StreetTitleSync in PostingFormStreetComboBox.SelectedItems.Title).Title

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