Add logic to commands with Power Fx

  • 5 minutes

Model-driven apps support a command bar at the top of forms and views where you can add custom buttons. Using Power Fx, you can control what happens when a button is selected, whether the button is visible, and how it interacts with the selected record.

What is commanding?

Commanding lets makers add custom buttons to the command bar of a model-driven app using the command designer. Rather than writing JavaScript, you write Power Fx expressions — the same formula language used in canvas apps — to define the button's behavior and visibility.

Note

Many Power Fx functions that work in canvas apps are also supported in commanding. Some functions are not supported, including Set(), Collect(), UpdateContext(), and others that rely on canvas-specific state management.

OnSelect

The OnSelect property defines what runs when a user selects the button. You can use any supported Power Fx function here.

For example, to update the name on the currently selected account record:

Patch(Accounts, Self.Selected.Item, {'Account Name': "Contoso"})

To navigate to a different screen or view:

Navigate(Accounts)

To show a confirmation dialog before taking action:

If(
    Confirm("Are you sure?", { ConfirmButton: "Yes", CancelButton: "No" }),
    Patch(Accounts, Self.Selected.Item, {Status: "Closed"})
)

Visible

The Visible property controls whether the button appears in the command bar. Set it to a Power Fx expression that returns true or false.

For example, to show the button only when one or more records are selected in a grid:

CountRows(Self.Selected.AllItems) > 0

To show the button only for records with a specific field value:

Self.Selected.Item.'Account Rating' > 20

The Selected property

Inside a command's Power Fx expressions, the Self.Selected object gives you access to the record or records that are currently selected in the app.

Property Returns Description
Self.Selected.Item Single record The currently selected record. Blank if nothing is selected or if multiple records are selected.
Self.Selected.AllItems Table of records All currently selected records. Empty if nothing is selected.
Self.Selected.State Enum Whether the form is in Edit (0), New (1), or View (2) state.

Notify the user

Use the Notify function to show a banner message to the app user after a command runs:

Notify("Record updated successfully.")

Next, you'll put your skills into practice by building a complete model-driven app in a hands-on exercise.