How do you select all items in a multi-select choice column in a SharePoint form?
For small choice fields with only two or three options this doesn’t matter too much, but if you have more than 4 options the missing select all is missing quite quickly.
Multi-Select choice columns
Table of Contents
In SharePoint you can have multi select columns. Within these column you can tick each option but there is no select all option available. This is quite annoying isn’t it?

We will need to customize the form. Customizing forms is done with Power Apps by selecting the customize with power apps option from the list menu.

We now want to add a checkbox to the form so that all options can be selected as shown below.

And none of the options should be selected when the tick box is deselected!

How to create the Select all?
In my form I located my Favourite Ice cream Multi-select field’s datacard, then I unlocked this field.

You will have to unlock the field otherwise you can configure the filtering as Power Apps doesn’t allow you to set anything within the datacard control unless it is unlocked.

You might have to position the check box correctly on the form. You can place it where ever you like as long as you stay within the form.

Now I set the DataCardValue2 (this is the one of my favourite icecream field) to SelectedItems. Selected Items will be a variable that I’m about to create in the next steps.
Setting the SelectedItems Variable
The OnSelect code for the CheckBox1 control now needs to be set to the following code:
If(
Checkbox1.Value,
Set(
SelectedItems,
[
"Vanilla",
"Strawberry",
"Chocolate"
]
),
Set(
SelectedItems,
[]
)
)
So depending on the value of the checkbox we will either set the Selected Items to an array of flavours or we simply set it to an empty collection []
Thanks for these steps! They work flawlessly on my Form, functionally speaking. I’m running into an issue though, where after my Form has been filled out, saved, and closed, when it’s re-opened, there are no longer selections in my field; it’s just completely wiped out. AKA if I’ve selected the checkbox previously, it re-opens as unselected, and if I’ve made single/multiple selections in my drop-down, instead of utilizing the checkbox to select all, those too disappear upon re-opening… Any thoughts what could be causing this? We’re trying to determine if there’s another specific code which also needs to be entered in another field to help retain the checkbox selection or the single vs. multiple drop-down selection.
It means that the records in the dropdown aren’t loaded properly. Sounds like a reset issue on the dropdown or datasource/collection used by the dropdown
Darn. The drop-down was working and retaining selections properly, until I added in the checkbox, so I’m thinking it’s not the drop-down that’s forcing things to reset. Thank you for the quick response though!