Build dialogs using model-driven pages to run flows all with low-code

Low-code is all the rush these days. It makes for more maintainable solutions that are built faster, specially when it comes to extending existing platforms like Power Platforms / Dynamics. It makes our work more decoupled from that of Microsoft’s and we can each focus on building better solutions without treading on each other’s toes. 😊

One of the main extension points in Power Platform is adding custom buttons to the Command bar. If you are not fully familiar with command bar, be sure to read the following article in the official docs to know what it is and where it is before reading further.

Command designer overview – Power Apps | Microsoft Docs

The previous experience was called Ribbon which is still around. If you would like to know more about this evolution, please read the following page from the official docs.

Command bar or ribbon presentation (model-driven apps) – Power Apps | Microsoft Docs

What are we building?

  • Reusable JavaScript library to open custom pages as dialog boxes
  • Custom button in command bar
  • Custom page in model-driven app to act as a dialog box
  • A cloud flow

In case you are wondering if this is a good practice to display custom pages in dialog boxes, this whole thing is recommended by Microsoft, but the only caveat right now is that Microsoft has not (yet?) provided a low-code solution to open custom pages. Instead, they have given us a list of JavaScript samples that can be used as starting points. I specially recommend you read the first article to have a good idea of where we are headed.

A cloud flow that can be triggered by apps

First things first, right? If we are building a dialog box to run cloud flows, we would first need a cloud flow. Anything would do, just remember it should be a flow that can be triggered by Power Apps and I strongly recommend to respond back with the result in your flow.

You’ll notice in the following screenshot that I have a flow that uses PowerApps (V2) as trigger and at the end it is returning two parameters as a result to any app that calls the flow.

Adding a Respond to a Power App or Flow at the end will let the caller (app or flow) to know if your flow has succeeded or not and the caller will have a chance to react accordingly.

A custom page in your model-driven app

Next step is to build a custom page that can be used as a dialog box. The goal of this custom page (which is a kind od Canvas app with some more power from model-driven apps by the way) is to help end-user run a flow (or several flows) and wait for them to complete while displaying a spinner and once the flow complete let the user know if something went wrong or simply disappear and refresh the data in the form.

To add a custom page to your model-driven app, you need to open the app in the new modern editor and click on the New Page button.

I suggest you build your custom page the responsive way, so you can display it in any kind of dialog no matter what size. To make a responsive page, I take the following approach.

As you can see on the image, I have one screen that contains a vertical container, an image called BusySpinner, a rectangle that fills the entire page to hide the content when the flow is ongoing.

In the VerticalContainer, I have two horizontal containers, the first one contains the only input parameter (language) I need to ask to user and the last one contains the OkButton. In your case you might need several horizontal containers. One per each parameter.

The visual layout of the page is similar to the following diagram. If it’s not clear enough, let me know in the comments and I will write all the properties you might need in a table here.

You will two variables to store the state of the page, IsBusy and IsValid.

  • IsBusy – this variable will have the value true when the cloud flow is executing and false when not.
  • IsValid – this variable will be false by default and will be true when all the required parameters are given by the end user and they are valid.

In your app’s OnStart you need the following commands to initialize the variables. I use this event to also initialize a simple collection I will use to fill a combo-box for my language parameter.

Set(IsValid, Not(IsBlank(Param("recordId"))));
Set(IsBusy, false);
If(Not(IsValid), Notify("Opportunity is not selected!"));
ClearCollect(LanguageCodes, "EN", "FR", "DE", "PT");

Next, you’ll need to add the cloud flow to your page, once you do that, you can trigger it in the OnSelect event of the OkButton.

Set(IsBusy, true);
Set(FlowResult,'Generatemandatedocument'.Run(Param("recordId"), LanguageOptions.Selected.Value));
    Notify(FlowResult.message, NotificationType.Success);Back(), 
    Notify(FlowResult.message, NotificationType.Error));
Set(IsBusy, false);

As you have noticed in the above code, I’m setting the IsBusy variable to true then I start the flow, while putting its result in a variable called FlowResult, this allows me to check the result of the flow in the line that follows. If the result is successful, I simply close the page (dialog), otherwise I’ll inform the user. At the end I set IsBusy to false.

To display the spinner and fade the content behind, when the flow is ongoing, you simply need to put the IsBusy in the Visible property of both BusySpinner and BusyOverlay.

You can also use the following expression in the DisplayMode property of the OkButton. This will disable the button when the flow is ongoing or when the input parameters are not valid.

If(IsValid And Not(IsBusy), DisplayMode.Edit, DisplayMode.Disabled)

Reusable JavaScript library to show custom pages in dialogs

Save the following script in a .js file (e.g. dialogs.js) and then open your solution in, and click on New, from the drop-down menu, open More and click on Web resource.

/* This function uses Navigation API to display a centered dialog. */
/* Simple parameters are used instead of object to make the function compatible with command bar parameters. */
function displayDialog(rowId, tableName, pageName, title, contentWidth, contentHeight, primaryControl) {
  const parseSize = (str, defaultStr) => (str || defaultStr || "500px").match(/([\d\.]*)(.*)/).splice(1,2);
  let [w, wUnit] = parseSize(contentWidth);
  let [h, hUnit] = parseSize(contentHeight);
    var pageInput = {
      pageType: "custom",
      name: pageName,
      entityName: tableName,
      recordId: rowId.replace(/[{}]/g, "")
    var navigationOptions = {
      target: 2, 
      position: 1,
      width: {value: parseFloat(w), unit: wUnit},
      height: {value: parseFloat(h), unit: hUnit},
      title: title
    Xrm.Navigation.navigateTo(pageInput, navigationOptions)
        function () {
            if (primaryControl.getFormContext) { primaryControl.getFormContext().data.refresh(); }
            else {;}
        function (error) {
          /* TODO: Add exception handling here. */

The above code is based on the Centered Dialog sample of Microsoft. I have only made a bit more production ready.

  • The whole script is a function that can be easily called from the new Command bar designer (still in preview).
  • Width and height have default values to be used in case no value is given by the custom button.
  • Curly braces are removed from rowId to make it Power App friendly.
  • When the dialog box closes, the content is refreshed.

Pay attention to lines 23 and 24 and see how I’m getting to the formContext object. It is done that way so you can use the same script from any flavor of command bar.

I recommend you improve the script to cover for some edge cases and more importantly add exception handling to notify the end-user properly if “something went wrong“. ☠

Adding a custom button to command bar

The new command bar editor can be found in the modern app editor (which is in preview at the time of this writing). You need to select an app in your solution and click on the three dots to open it context menu and select Edit in preview item. Just like the following screenshot.

Once in the new App editor, scroll down to the table where you its command bar to receive this fancy new button. In the following screenshot, you’ll notice I’m editing the command bar of Opportunity table.

Power Platform will ask you which command bar you are interested in. I am going to choose Main form, but in case you are wondering what are these options, you need to read the first link I have shared in the beginning of my post 😉.

Once in the command bar editor, add a new button with the following properties.

LabelRun my flow (can be anything you want).
ActionRun JavaScript (in future I hope we will be able to use PowerFx instead).
LibraryThe name you gave to your web resource. I used fancy_dialogs for example.
If you can’t find your library in the list you will need to click on the pen icon just besides the drop-down menu.
Function namedisplayDialog
Parameter 1FirstPrimaryItemId
Parameter 2String | opporunity (this should be the logical name of your table)
Parameter 3String | fancy_flowlauncher (this should be the name of your custom page)
Parameter 4String | Run flow (this will be the title of your dialog)
Parameter 5String | 500px
Parameter 6String | 500px
Parameter 7PrimaryControl

If you have followed all the steps correctly, the end result should be similar to the following.

Power Platform Tidbit #5 – What events are available in model-driven apps

Model-driven Power Apps can notify your code when certain events happen in the following parts of your apps.

  • Form
    • OnLoad – when form loads.
    • OnSave – when data is saved.
  • Tab
    • TabStateChange – when a tab expands or collapses.
  • Column
    • OnChange – when data changes in the column and its control loses focus.
  • IFrame –
    • OnReadyStateComplete – when the content of IFrame is fully loaded.


  • TabStateChange is the best event to set the src property of an IFrame in a tab. If you otherwise do it in OnLoad event for a an IFrame that is in a collapsed tab, it will be overwritten when the tab expands!
  • OnChange happens immediately for Yes/No buttons that are formatted to use checkbox or radio buttons.
  • OnChange happens also when the data is changed on the server and the form refreshed (e.g. after a record is saved).
  • You can also trigger OnChange by calling attribute.fireOnChange.
  • Make sure to read the official docs about OnChange events. They can be tricky.
  • Try to always stick with these main events, but you can find all events that are available to you in JavaScript in here.

Reference: Configure model-driven app form event handlers

Power Platform Tidbit #4 – Workflows in Business process flows

Business process flows guide people in a stage by stage and step by step flow to get the work done consistently. The process – like anything in Power Platform – can be tailored to security roles of the users. Very often you would need to trigger workflows as users start or complete these flows or when they transition between different stages.

The two types of triggers

Workflows can be either global within the business process flow or they can be called as stage transitions.

  • Stage transition workflows can be triggered by:
    • Stage Entry
    • Stage Exit
  • Global workflows can be triggered by:
    • Process applied (*) – When business flow starts.
    • Process abandoned – When user abandons the flow and it is archived.
    • Process reactivated – When user starts and abandoned flow.
    • Process completed (*) – When user clicks to finish the last stage of the flow.

You should keep in mind that Stage Entry an Stage Exit will not be triggered for the first and last stage respectively. If you need to trigger a workflow for those situations you should rely of global workflows that are triggered by Process applied and Process completed events.


Power Platforms Tidbits #3 – Power Automate flow types

There are five types of flows in Power Automate depending that you can build. Three of them are considered cloud flows.

  • Cloud flows
    • Automated flows
    • Instant flows
    • Scheduled flows
  • Desktop flows
  • Business process flows

Cloud flows

Cloud flows can be either of the following.

  • Automated flows – that are triggered when an event happens. For example when an account is updated.
  • Instant flows – that are triggered manually by a user or even a Virtual Agent.
  • Scheduled flows

Desktop flows

Desktop flows are run using Power Automate for desktop, which is replacing the two legacy options which we had before for Windows and web applications. Namely Windows recorder (V1) and Selenium IDE.

Business process flows

  • Business process flows guide users, step by step to make sure everyone on the team is following the same steps and entering data consistently.
  • You can have up to 10 concurrent business process flows per table that user can switch between and continue at any time.
  • As a bonus you can even run workflows when a user enters or leaves a workflow.

Useful tips!

  • There is an interesting tool called Process Advisor “that quickly captures detailed steps for each process in your organization to help you better understand places to streamline workflows. You can do this on your own or invite colleagues to contribute and collaborate”. Read more here: Overview of process advisor
  • Keep in mind that Power Virtual Agents can call your Instant flows. It means you can have Virtual Agents that not only reply to and guide users but take initiatives!
  • Try as much to standardize business processes in organizations as Business process flows. This approach will reduce human errors and makes it easier for every one to learn and work with the system.


Power Platform Tidbits #2 – What is possible with business rules in Model-Driven Apps vs Canvas Apps

Business rules can be used by Canvas Apps or Model-driven Apps to do the following:

  • Set column values.
  • Clear column values.
  • Validate data and show error messages.

But keep in mind that they can do the following only in model-driven apps:

  • Show or hide columns.
  • Enable or disable columns.
  • Create business recommendations based on business intelligence

Reference: Define and create business rules in Dataverse